Doi:10.1016/j.rvsc.2007.08.009

Available online at www.sciencedirect.com Research in Veterinary Science 85 (2008) 26–34 Cushing's disease in dogs: Cabergoline treatment V.A. Castillo *, N.V. Go´mez, J.C. Lalia, M.F. Cabrera Blatter, J.D. Garcı´a Hospital Escuela-Unidad de Endocrinologı´a, A. Clı´nica Me´dica de Pequen˜os Animales, Fac. de Ciencias Veterinarias-UBA, Av.
Chorroarin 280, 1427 C. Buenos Aires, Argentina Accepted 11 August 2007 The treatment of pituitary-dependent hyperadrenocorticism (PDH) in dogs has for a long time been focused on inhibiting the adrenal gland using drugs such as o–p0-DDD, Ketoconazole and Trilostane, without attacking the primary cause: the corticotrophinoma. Cor-ticotroph cells can express the D2 dopaminergic receptor; therefore cabergoline (Cbg) could be effective as a treatment. Follow-up over 4years was carried out in 40 dogs with PDH that were treated with Cbg (0.07 mg/kg/week. Out of the 40 dogs, 17 responded to Cbg(42.5%). A year after the treatment, there was a significant decrease in ACTH (p < 0.0001), a-MSH (p < 0.01), urinary cortisol/creatinineratio (p < 0.001), and of the tumor size (p < 0.0001) evaluated by nuclear magnetic resonance. Dogs responding to Cbg lived significantlylonger (p < 0.001) than those in the control group. To conclude, Cbg is useful in 42.5% of dogs with PDH, justifying its use as atreatment.
 2007 Elsevier Ltd. All rights reserved.
Keywords: Hyperadrenocorticism; Cushing's disease; Corticotrophinoma; Cabergoline; D2 dopamine receptor adenoma, we have recently shown that 9-cis retinoic acid iseffective to control PDH in dogs, as it had been previously The treatment of the pituitary-dependent Cushing's dis- reported in mice ), causing a ease (PDH) or Cushing's disease (CD) in dogs has for a reduction of the tumour and the inhibition of the synthesis long time been mainly focused on the inhibition of the secretion of cortisol by means of drugs that act on the adre- The presence and inhibitory action of dopaminergic nal gland, either by causing its necrosis or by inhibiting the receptors in the anterior pituitary lobe was discovered synthesis of steroids Dopaminergic drugs (such as bromo- ). Although the solution criptine) have been tested for the treatment of PDH with would be the removal of the pituitary tumor, the problem varying success ( in veterinary cases lies in the fact that the whole pituitary gland is removed and not only the diseased area The debate as to the use of these types Radiotherapy has also been proposed as a of drugs arises due to the different opinions on the genesis therapeutic method, the problem being not only the cost, of the corticotroph adenoma ( but also the high risk of damaging the optical chiasm or as well as the results obtained. It has been the surrounding brain tissue widely accepted that the origin of the corticotroph ade- With regard to drugs that act upon the synthe- noma is monoclonal, but the theory that an over stimula- sis and release of ACTH and also control the corticotroph tion of the corticotroph area of the hypophysis by thehypothalamus (increase in ACTH [CRH] releasing factor or reduction of the dopaminergic tone) may bring about Corresponding author. Tel./fax: +54 11 4524 8496.
E-mail address: (V.A. Castillo).
the development of neoplasia, after a first stage of 0034-5288/$ - see front matter  2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.rvsc.2007.08.009 V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 hyperplasia, has not been ruled out clinical signs characteristic of the disease ( ), cortisol: creatinine ratio in urine greater than has been described that both the degeneration of dopami- 70 nmol/L with elevated plasma ACTH and evidence of a nergic neurons and the loss of D2 receptors due to age, pituitary tumour or abnormal PI appearance detected by affects the actions of dopamine (DA), both in the central nuclear magnetic resonance imaging (NMRI).
nervous system as well as in the negative regulation on The dogs' average age was 9 (range 3–14 years old), 40% the hypophysis, especially on the lactotroph and cortico- of them being mixed-breed and the rest of several breeds: troph cells of the pars intermedia (PI) Poodle, German Shepherd, Beagle, Boxer, Doberman, This age-related neurodegener- Daschund, Syberian Husky, Samoyedo, Shetland Sheep ation has also been described in dogs therefore, the reduc- dog, Standard Schnauzer. All cases were sent to the Endo- tion of DA would lead to the lifting of the hypothalamic crinology Unit of the Veterinary School Hospital of the inhibition and chronic stimulation of the CRH over the Faculty of Veterinary Sciences of the University of Buenos corticotroph area, causing its hyperplasia ( Aires and had the written consent of their owners to partic- On the other hand, both ipate in the study.
describe a reduction in Dogs were divided into two groups in the following the synthesis and actions of dopamine in cases of chronic manner: every 3 cases, the first one was incorporated to stress, resulting in a greater activation of the hypothala- the control group (up until 23 cases) and the following 2 mus-pituitary-adrenal axis (HPA) and in hyperplasia of cases into the Cbg group (up to 40 cases). This was done the corticotroph cells. It is known that the pars intermedia so as to end up with the same amount of cases in both con- (PI) of the pituitary is negatively neuro-regulated by DA, trol and Cbg groups, based on a previous experience in inhibiting in this way the synthesis of the melanocyte-stim- nude mice with an implanted ACTH secreting adenoma ulating hormone (a-MSH), and it has been described in the where approximately 50% did not respond to Cbg. Thus, dog that the corticotroph cells of the pars distalis (PD) may the resulting groups were: also be inhibited by DA Control group (Ketoconazole group): 23 dogs (13 female In dogs the corticotropinoma's origin may [9 non-castrated] and 10 male) which received ketoconazole be either from the PD, the PI or indeed be of mixed origin (Ktz, 20 mg/kg/day), this being the conventional therapy (). PI tumours are resistant to the sup- for canine Cushing's syndrome in Argentina. This was used pressive effects of dexamethazone as a control because of ethical and legal reasons that do not allow us to leave animals without a proven treatment.
Cabergoline (Cbg) is a dopamine D2 receptor agonist The Cbg group: 40 dogs (26 female [15 non-castrated] with a higher affinity and a longer half-life than bromocrip- and 14 male) which received a total of 0.07 mg/kg Cbg tine (In humans, its effectiveness and per week, dividing the dose into 3 and giving one every tolerance in the treatment of prolactinomas ( 48 hours. Cases where there was no response to Cbg within ) and growth-hormone secreting adenomas 3 months after starting the treatment or when there were (have been demonstrated. side effects ascribed to the therapy that put the animal's life describe reduction in size of the aggressive cor- at risk were withdrawn from the study and transferred to ticotroph adenoma which causes Nelson's Syndrome, while the conventional therapy used in Argentina (in accordance the anti-neoplasic effects of Cabergoline have been reported with the ethics committee's indications) and therefore were to be effective in the treatment of non-functional tumours not evaluated statistically nor incorporated in the Ktz of corticotroph cell ( group. The group with those dogs that continued with describe the presence of D2 receptors in a cor- Cbg was renamed: Cbg responding treatment (CbgRT).
ticotroph adenomas in a patient with Nelson's Syndrome.
As a clinical follow-up, the following parameters of As the usefulness of Cbg in the treatment of PDH in objective evaluation, as well as those highly frequent in dogs had not been studied, and taking into account the dogs with PDH ), were controlled: pres- neurophysiological characteristics of the canine hypophysis ence or absence of polydipsia–polyuria (Pd–Pu), urine den- sity, polyphagia (Pf), size of abdomen (prominent or we decided to treat a group of dogs with PDH normal), weight (kg) and return to oestrous cycle in with Cbg with the purpose of evaluating the effectiveness of females. The appearance of the skin (elasticity, thickness this drug in the therapy of the disease.
and pigmentation) and of the hair (alopecia and signs suchas 2. Materials and methods Response to the treatment was considered positive if within3 months the following improvements were observed: sus- 2.1. Population under study pension or reduction of Pd–Pu (liquid intake <100 ml/kg/day), increase of urine density, and at least a 5% reduction A single-blind, longitudinal study, with a 4 year follow- in weight, compared to the initial weight. It was deemed up, was performed in 63 dogs with PDH, diagnosed that there had been a full response to the treatment if according to the following criteria: presence of at least 4 besides continuing with the normalization of the above V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 mentioned parameters, there was evidence of normaliza- cortisol to creatinine. (measured in Metrolab Autoanalizer tion of the endocrine-biochemistry and a reduction of the Merck, Germany, according to the manufacturer's indica- size of the adenoma or of the aspect of the PI in the images tions). The inter- and intra-assay coefficients of variation after one year of treatment.
for cortisol were 8% and 5%, respectively.
Evaluations of ACTH and C/CR were repeated every 2.2. Diagnosis of Cushing's disease and follow-up of groups year for four years, while the a-MSH was only repeatedafter one year of treatment.
The PDH diagnosis protocol (Endocrinology Unit, Fac- ulty of Veterinary Sciences of the University of Buenos 2.4. Statistical analysis Aires) was based on: (1) an increase of urine clearance ofcortisol (evaluated through the cortisol/creatinine ratio in Student's t-test was used for the analysis of the same urine, C/CR) with inadequate high concentrations of group and the unpaired t test was used to compare both plasma ACTH, and (2) a reduction of the C/CR to more groups, both before the treatment and after 1 year of treat- than 50% of the basal value of C/CR previously obtained ment. The Wilcoxon's test and the Mann–Whitney's test were used in those cases deemed necessary, according to after oral administration of 0.1 mg/kg of dexamet- results of the normality test of the variables under study.
hazone every 8 h. Confirmation of the pituitary adenoma The survival curve was performed and evaluated according was obtained through nuclear magnetic resonance imaging to the log-rank v2 test. The Odds ratio (OR) was calculated (NMRI), with sections every 2 mm. To evaluate the by means of the v2 test (contingency table and Fisher's appearance of the adenoma, the sagittal section was taken exact test), as well as if the clinical improvement was due through the middle line, classifying the tumours into intra- to the use of Cbg. Values are expressed as means ± stan- sellar (65 mm) and extra-sellar (P5.5 mm) according to dard deviation (SD), median and range, as applicable, with the phases described by and validated a significance level of 0.05.
by our previous observations in normal dogs and dogs withPDH. With this same sagital section, the appearance of the 2.5. Ethical approval PI was studied (abnormal: image of more than 0.5 mm ofthickness at the sagittal section, without an openly visible The study was approved by the Ethics Committee of the signal to the gadolinium enhancing, according to our Faculty of Veterinary Sciences of the University of Buenos observations in healthy dogs). The size of the adenoma Aires and by the Secretarı´a de Ciencia y Te´cnica (Secretar- was measured through the transversal section, calculating iat of Science and Techniques) of the said University the greatest diameter or height (greatest height from the (UBACyT; V045 project) in fulfilment of the national laws base to the highest point of the section) and the tumour on experiments with animals. Dog owners gave their signed surface by multiplying the height (greatest diameter of consent for the participation of their animals in this study.
the tumour in the transversal section) by the width(height · width = mm2). A pituitary with a normal appear- ance in a NMRI is equivalent to ‘‘0'' mm. The imagesobtained by NMRI were repeated after one year of treat- 3.1. Response to treatment and survival ment with Cbg and after 4 years, and were performed bythe same operator. The coefficient of variation between The only side effect in the dogs receiving Cbg was vom- studies was of ±0.5 mm.
iting, which occurred one hour after taking the first dose in90% (36/40) of the animals. Only 10% repeated the vomit- 2.3. Hormone measurements ing with the second dose, and there was no report of emesiswith the third dose.
Plasma ACTH concentration was measured by means of Out of the 40 dogs treated with Cbg, 24 (60%) the immunoradiometric assay (IRMA) using an available responded after the first month and 16 (40%) did not commercial kit (Nichols Advantage ACTH Assay, Nichols respond after 2 months of having begun the study and Institute Diagnostics, Bad Vilbel, Germany). The a-MSH hence were switched to receive Ktz at the above mentioned (Euro-Diagnostica AB, Malmo¨, Sweden) was obtained dose. Of the dogs that responded to the treatment, 7/24 with the same sample as the ACTH and measured by (29%) showed a favourable initial response (improvement means of the radioimmuno assay (RIA), the plasma being of the clinical signs) which lasted between 4 and 6 months frozen at 80 C until its processing. The intra-assay and depending on the dog, to afterwards become non-respon- inter-assay coefficients of variation for ACTH were 3% dent (with a return of the clinical signs and persistence of and 6.8% respectively; and for a-MSH were 2.9% and a high C/CR), being switched to treatment with Ktz. These 4.0%, respectively.
dogs were removed from the study. Therefore, dogs with a Urine cortisol was measured by means of RIA, using a full response to the treatment with Cbg (CbgRT) ended up commercial kit (DPC Corporation, San Diego, California, being 17/40 (42.5%) composed of 6 non-castrated females USA). The urine cortisol was expressed as a ratio of urine and four castrated.

V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 When looking at the clinical signs evaluated (), the most conclusive response to the treatment with Cbgwas the normalization of the water intake, already men-tioned by the owners within two months of having startedthe treatment, and consequently, a decrease in the fre-quency of urination, accompanied by the significantincrease in urinary density after one year of treatment whencompared to the pre-treatment baseline value (1010 ± 4.57vs. 1019 ± 4.98; p < 0.0001). Weight reduction was also sig-nificant after one year of treatment (p < 0.01). Theseimprovements were predictably also present in the Ktzgroup, and no significant differences were found betweenboth groups.
The oestrous cycle returned in five of the non-castrated females in the CbgRT group. On the other hand, only onefemale dog of the 10 non-castrated females of the other Fig. 1. Survival curve in dogs with pituitary-dependent Cushing'ssyndrome: comparison of those CbgRT vs. those unresponsive and group returned to oestrus, this difference being significant treated with Ktz. After diagnosis, 50% of the dogs in the Ktz. Group die (p < 0.01) when comparing both groups, with an OR = 50.
approximately 1.8–2 years (range 0.6–3) vs. animals in the CbgRT group Regarding dermatological signs, 3 dogs in the CbgRT (***, p < 0.001), where the average survival time was 3 years (range 1–4). In group that showed hyperpigmentation when the disease this last group, 41% (7/17) of the dogs live 4 years after having been was diagnosed, returned to their normal skin colour after diagnosed and started treatment with Cabergoline. As opposed to the Ktz.
Group, none of these dogs died from complications of Cushing's Disease, 3 months of treatment (2 of them had an increased PI).
but due to age-related causes (>13 years; log-rank test v2).
In the following years, the clinical signs evaluated remained unchanged when compared to the ones observedat clinical diagnosis of the disease (data not shown).
Ktz group 52.2% (12/23) had tumours with extra-sellar Survival after initiation of treatment was significantly projection, 30.4% (7/23) intra-sellar and the others showed longer in the CbgRT compared with Ktz group ).
an affected PI, with the range of age being similar to that in Seven out of the 17 dogs in the CbgRT group completed the CbgRT group.
the 4 years of study and follow-up. After one year of treat- In the CbgRT group, diameter and surface of the ment, the survival rate was already different between the tumours were significantly reduced (p < 0.0001) compared two groups (p < 0.01) with an OR = 19.2.
to the baseline values and compared to the Ktzgroup after one year of treatment (p < 0.0001). This implies 3.2. NMRI pituitary evaluation pre- and post-treatment an average reduction of the diameter and of the surface of31.4% and 38.6%, respectively. In the Ktz group, there Of the dogs treated with Cbg, 55% (22/40) had tumours were no differences in the analyzed values (diameter and with extra-sellar projection, 27.5% (11/40) with intra-sellar surface). Animals with altered PI images presented similar projection, and 17.5% (7/40) showed an increase in the size characteristics to the normal pituitary.
of the PI in the sagittal section of the NMRI but without When analyzing the response or lack of response to Cbg evidence of tumour ). It is necessary to stress that in connection with the size of the tumour or its the average age of the 7 dogs with the affected PI was intra- or extra-sellar projection, dogs that did not respond 10.8 years (range 8–14), this being significant (p < 0.05) to Cbg (16/40 dogs) presented a significantly greater when compared to dogs (33/40) with evident pituitary tumour size than those which were responsive (diameter tumours in PD (mean age 8.7; range 3–13 years). In the p < 0.01 and surface p < 0.01), with only 2 out of 16 unre- Table 1Changes in clinical signs in dogs with PDH treated with 0.07 mg/kg/week of cabergoline (CbgRT) compared with 20 mg/kg/day of ketoconazole (Ktzgroup) Post-treatment (1 year) Post-treatment (1 year) Water intake (Pd–Py/normal) Polyphagia (with/withou Skin and hair d (abnormal/normal) Pre-treatment and post-treatment CbgRT n = 17, pre-treatment Ktz n = 23, post-treatment Ktz n = 17 (see text). All data are expressed as number ofcases (with alteration in sign/improved or normal sign). Contingency table and Fisher's exact test were used for statistical analyses. OR represents oddsratio for post-treatment CbgRT vs. Ktz group.
* P < 0.05 post Cbg vs. post Ktz; dP < 0.05 post Cbg vs. post Ktz, NS: not statistic differences (P = 0.08) post Cbg vs. post Ktz.

V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 Fig. 3. Size of the ACTH producing pituitary tumour: diameter (a) andsurface (b). It is evident that both measurements are greater at the time of Fig. 2. Nuclear magnetic resonance imaging (gadolinium enhanced) in the diagnosis and beginning of the treatment in the Ktz. Group (diameter, dogs before and after 1 year of treatment with Cbg. a–b supra-sellar ** p < 0.01; surface, ** p < 0.01). After one year of treatment, tumour size adenoma (both transverse sections).The reduction in the tumour size can is reduced in dogs in the CbgRT group vs. their baseline values (both be appreciated in both cases. c, image of the increased PI (doted circle measurements, *** p < 0.0001) as well as compared to those in the Ktz.
around PI; arrows point to dark thick line which indicates the lack of Group (both measurements, *** p < 0.0001). Values are expressed as signal on MNRI) compared to a normal one (right and post-treatment) mean ± SD. Unpaired t-test (CbgRT vs. Ktz comparison) and Student's visible in the sagital section. These images did not show changes on the t- test (same group). CbgRT fourth year of evaluation in dogs in the CbgRT group that continue alive.
b, Ktzb = responsive and ketoconazole groups respectively, basal values at the time of diagnosis and beginning oftherapy; CbgRT 1y, Ktz 1y = 1 year of follow-up of the treatment. Shaded sponsive tumours being intra-sellar. All dogs whose PI was squares = CbgRT, open triangles = Ktz.
affected showed a full response to Cbg. After 4 years of fol-low-up, the 7 dogs in the CbgRT group presented a normalpituitary image (data not shown).
Once the dogs in the CbgRT group were separated into those with a tumour and those with a PI with increased size 3.3. Hormone analysis in the NMRI, it became evident that the a-MSH had signif-icantly higher values in the 7 dogs with altered PI image Concentration of ACTH and a-MSH of the 17 dogs in compared to the rest of the animals of that group the CbgRT group () was significantly reduced after (97.34 ± 42.5 pmol/L vs. 25.1 ± 10 pmol/L; p < 0.0001) one year of treatment compared to the baseline values before starting the treatment.
(ACTH, p < 0.0001; a-MSH, p < 0.01) and compared to The C/CR in the CbgRT group (showed signifi- dogs in the Ktz group (ACTH, p < 0.0001, a-MSH cant differences (p < 0.001) with the baseline value, with no p < 0.01). ACTH in the CbgRT group remained within significant changes in the subsequent evaluations (data not the normal range in the subsequent re-evaluations (data shown). The C/CR was also reduced in the Ktz. group not shown), without significant differences after 4 years (p < 0.0001) after one year, also showing differences with vs. 1 year of therapy. The Ktz group evidenced a signifi- the values of the CbgRT group after one year of treatment cant increase (p < 0.0001) of ACTH after one year of (p < 0.05). As with ACTH, the C/CR did not show signif- receiving the drug, but no significant differences in a- icant variations in successive evaluations, remaining within the normal values with no significant differences after 4

V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 Fig. 5. Changes in the urine cortisol/creatinine ratio in dogs thatresponded to treatment with cabergoline (CbgRT) vs. the unresponsivegroup treated with Ketokonazol (Ktz). Reduction is significant in bothgroups after one year of treatment (CbgRTb vs. CbgRT 1y, *** p < 0.0001and Ktzb vs. Ktz 1y, +++ p < 0.0001). However the reduction is mostevident in CbgRT 1y vs. Ktz 1y, d p < 0.05. Values are expressed as medianand ranges, Mann–Whitney's Test (CbgRT vs. Ktz comparison) andWilcoxon's Test (intra-group). CbgRTb, Ktzb = responsive and ketocon-azole groups, basal values at the time of diagnosis and beginning oftherapy respectively; CbgRT 1y, Ktz 1y = 1 year of follow-up oftreatment. Shaded squares = CbgRT, open triangles = Ktz.
so-called Nelson's Syndrome ).
Cbg has been shown to have a positive effect in humans with those tumours that express the D2 dopaminergic Fig. 4. Changes in ACTH and a- MSH in dogs CbgRT vs. Ktz group. a, receptor, especially prolactinomas and somatotrophinomas ACTH after one year of treatment (CbgRT 1 y) vs. CbgRTb and vs. Ktz 1y, *** p < 0.0001. Using Ktz, after one year of treatment (Ktz 1y) ACTHincreases +++ p < 0.0001 vs. baseline values (Ktzb). b, a-MSH in CbgRT show that in the corticotroph tumour cells, the D2 1y vs. CbgRTb, ** p < 0.01, CbgRT 1y vs. Ktz 1y, ** p < 0.01. This receptor is expressed in 80% of them, being functional in hormone did not present significant changes after one year in the Ktz 60%, and they conclude that the therapy with Cbg would group vs. its baseline values. Values are expressed as means ± SD.
be effective in 40% of the cases, and therefore it would be Unpaired t-test (comparison CbgRT vs. Ktz) and Student's t-test (intra- acceptable to use dopaminergic drugs (such as Cbg) for group). CbgRTb, Ktzb = responsive and ketoconazole groups respectively,basal values at the time of diagnosis and beginning of therapy; CbgRT 1y, the treatment of PDH. This finding is confirmed in our Ktz 1y = 1 year of follow-up of the treatment. Shaded squares = CbgRT, study on dogs. Although there was an initial favourable open triangles = Ktz.
response in 60% of the cases, Cbg was ultimately usefulin 42.5% of the treated dogs, agreeing with the above men-tioned authors. Improvement in the clinical signs evaluated years of follow-up vs. 1 year of therapy in the CbgRT occurred without side effects, normalization of the ACTH group (data not shown).
and a-MSH concentration and C/CR, reduction in thetumour size or PI image and prolonged survival time were achieved with Cbg.
From a clinical point of view, it was possible to see a The functional corticotroph adenoma that causes PDH, favourable evolution, especially concerning recovery of has been and is currently under study as a therapeutic tar- the oestrous cycle. This event marked the difference in get for different drugs both in dogs and humans ( the clinical response of the CbgRT group compared to the other group. The inhibiting action of cortisol over Although control of corti- the reproductive function is known ( sol is achieved with the drugs that act upon the adrenal, the tumour that produces ACTH continues synthesizing the the dog with PDH has hypogonadism–hypogonadotro- hormone, resulting in an increase of ACTH secretion and phism and an increase of prolactin (PRL). In this sense the risk of growth of the tumour Cbg, as the negative action of cortisol over the gonadal axis ). This is similar to what happens ceases, besides normalizing the PRL as is widely known, when an adrenalectomy is performed, bringing about the shows its positive action by normalizing the adrenal axis.
V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 These events are decisive for the return of the female's the corticotroph adenoma ( reproductive function; and possibly of the male's too, ). On the other hand, resistance to the inhib- where the sexual dimorphism observed in the corticotroph iting action of glucocorticoids observed in macroadenomas cells must be taken into account (The other clinical signs which should be emphasized are the accompanied by high levels of cortisol, bringing about a decrease in water intake and frequency of urination, events greater reduction in DA and its receptors ( that occur early on during the treatment with Cbg, indicat- ing control of cortisol secretion and its action on the renal In this way, Cbg would have no effect or its effect function With respect to the others signs would be partial. On the other hand, the existence in dogs evaluated, their improvement was greater in the CbgRT of tumours of mixed origin may group than in the Ktz group, already evident after 1 year explain the initial favourable response to afterwards escape of treatment.
from Cbg. Conversely, the favourable response in the intra- Regarding the effects on the synthesis of ACTH and sellars (except for two cases) leads one to think of a greater a-MSH, the inhibition exercised by Cbg over these hor- functional expression of the D2 receptor or that one is in mones (with the corresponding reduction of the C/CR) is the presence of a hyperplasia of the corticotroph area with clear. This makes it evident that in animals responding an adenomatous aspect. These concepts are strengthened favourably, the D2 dopaminergic receptor must be by the observed tumour reduction (both in those of extra- expressed; otherwise there would not be any response. On sellar as well as intra-sellar projections that responded) the contrary, and as expected, ACTH increased in the other and are indicative of a regulatory and proapoptotic action group. This increase is attributable to the reduction of cor- tisol (reflected by the C/CR) due to the effect of Ktz, alter- described by .
ing the negative regulating action that it exercises over the It is important to emphasize the conclusive effect in the 7 corticotroph area, even in individuals with corticotroph dogs that presented the altered PI image, and whose aver- age age was 10.8 years. This is a clear indicator that Cbg ). It is important to point out that the reduction of normalizes the dopaminergic system and the regulation of the C/CR in the Ktz group was not as evident as in the this lobe. This positive action on the PDH originating in group treated with Cbg. This is caused by the persistent the PI is perfectly reflected, not only by the clinical and stimulation of the adrenal due to the increase in ACTH endocrine-biochemical progress observed, but also by the in this group, as has also been previously mentioned ( normalization of the image observed in the NMRI. In these Evidently, by inhibiting the synthesis of dogs, the cause of the disease would be a consequence of ACTH and the adenoma that produces this hormone, the the degeneration of dopaminergic neurons caused by age, result of administering Cbg will be a physiological regula- with a reduction of DA and the deregulation of the cortico- tion of the adrenal steroidogenesis.
troph area of the PI (), as well as of the PD Full therapeutic response is less than expected, which (). When DA decreases, the action of could be due to how the D2 receptors are expressed in dogs the proconvertase 2 (PC2) is reduced, and therefore, the (and maybe in humans too). The evidence that Cbg has a cleavage of ACTH in a-MSH (This brings different effect to other dopaminergic drugs such as bromo- about an increase in the first hormone and the development criptine over the corticotroph adenoma that expresses D2 of hyperadrenocorticism receptors, could be due to their different molecular struc- Therefore, by normaliz- tures and pharmacological actions, especially the greater ing the DA, the action of PC2 and the concentrations of affinity for the D2 receptors and the longer action of Cbg ACTH and a-MSH are normalized. One then obtains a compared to bromocriptine double beneficial effect of Cbg in treating the PDH: its anti- ). This may possibly be explained in connection proliferative and proapoptotic action and its effect over the with the tumour size, the origin of the corticotroph ade- dopaminergic system and the subsequent normalization of noma or the molecular characteristics of the D2 receptor the enzymatic system of the proconvertases. Reduction of the tumour size and improvement of the PI aspect, evi- greater tumour size in dogs that did not respond to Cbg denced in CbgRT but not Ktz group, is a clear demonstra- leads one to believe that in these cases Cbg is perhaps less tion of the proapoptotic and inhibitory effects of Cbg on effective, because these macroadenomas present a different the corticotroph adenoma and DA system.
behaviour and molecular origin to the tumours in intra-sel- The lack of serious side effects, without alteration of the hepatic enzymogram, or of the glucose or the lipid profiles It is probable that they have lost the expression of the D2 (data not shown), make Cbg a safe long-term drug. The receptor, or that these receptors are expressed in a lower dogs' survival has been encouraging, because the average quantity or that they are not functional because they expected life-time with classical treatments is of approxi- express another isoform or then again that they never Unfortunately, this happened with those animals expressed the receptors, taking into account the genesis of treated with ketoconazole.
V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 The fact that after 4 years none of the dogs in the 2006. Retinoic acid as a novel medical therapy for Cushing's disease in CbgRT group presented clinical signs again and that the dogs. Endocrinology 174, 4438–4444.
Casulari, L., Naves, L., Mello, P., Neto, A., Papadia, C., 2004.
endocrine-biochemistry remained normal, is an indication Nelson's syndrome: complete remission with cabergoline but not that Cbg exercises a long lasting control over the disease, as was observed by and by Research 62, 300–305.
Colao, A., Lombardi, G., Annunziato, L., 2000. Cabergoline. Experi- Thus, one can conclude that with 42.5% of the cases mental Opinion Pharmacotherapy 1, 555–574.
Colao, A., Di Sarno, A., Pivonello, R., Di Somma, C., Lombardi, G., showing a favourable response the use of Cbg as a treat- 2002. Dopamine receptor agonists for treating prolactinomas. Exper- ment for PDH is justified, especially if we take into account imental Opinion Investigation Drugs 11, 787–800.
the actions of this drug both over the tumour as well as Dahia, P.L., Grossman, A.B., 1999. The molecular pathogenesis of over the function of the dopaminergic system. In the case corticotroph tumors. Endocrinology Review 20, 136–155.
of intrasellar tumours (no bigger than 5 mm) or when the de Herder, W., Reijs, A., Kwekkeboom, D., Hofland, L., Nobels, F., Oei, H., Krenning, E., Lamberts, S., 1995. In: vivoimaging of pituitary PI is affected, this would be the primary drug indicated.
tumours using a radiolabeled dopamineD2 receptor radioligand.
In cases of neoplasias of extrasellar projection, it could Clinical Endocrinology (Oxf) 45, 1996, pp. 755–767.
be effective or not, depending on the expression, isoform Dong, W., Day, R., 2002. Gene expression of proprotein convertases in and/or function of the D2 dopaminergic receptors. In this individual rat anterior pituitary cells and their regulation in cortico- case, a correct therapeutic management would be to sus- trophs mediated by glucocorticoids. Endocrinology 143, 254–262.
Feldman, E.C., Bruyette, D.S., Nelson, R.W., 1990. Plasma cortisol pend the treatment if there is no response in 3 months, or response to ketoconazoles administration in dogs with hyperadreno- if the clinical signs and the endocrine-biochemical altera- corticism. American Journal Veterinary Medical Association 197, 71– tions typical of the disease return.
Galac, S., Kooistra, H., Teske, E., Rijnberk, A., 1997. Urinary corticoid/ creatinine ratios in the differentiation between pituitary-dependenthyperadrenocorticism and hyperadrenocorticism due to adrenocorticaltumour in the dog. Veterinary Quarterly 19, 17–20.
The work was financed by the Secretarı´a de Ciencia y Giros, B., Solokoff, P., Martres, M.P., Riou, J.F., Emorine, L.J., Te´cnica of the University of Buenos Aires (UBACyT, Schwartz, J.C., 1989. Alternative splicing directs the expression of VO45). We wish to thank Dr. Farfallini for performing two D2 dopamine receptor isoforms. Nature 342, 923–926.
the magnetic nuclear resonance imaging in the dogs.
Gittoes, N.J., 2005. Pituitary radiotherapy: current controversies. Trends Endocrinology Metabolism 16, 407–413.
Goossens, M., Feldman, E., Theon, A., Koblik, P., 1998. Efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadren-ocorticism. Journal American Veterinarian Medical Association 212, Abs, R., Verhelst, J., Maiter, D., Van Acker, K., Nobels, F., Coolens, J.L., et al., 1998. Cabergoline in the treatment of acromegaly: a study in 64 Gore, A., Attardi, B., DeFranco, D., 2006. Glucocorticoid repression of patients. Journal of Clinical Endocrinology and Metabolism 833, 74– the reproductive axis: effects on GnRH and gonadotropin subunit mRNA levels. Molecular and Cellular Endocrinology 256, 40–48.
Antakly, T., Mercille, S., Cote, J.P., 1987. Tissue-specific dopaminergic Heren˜u´, C., Brown, O., Sosa, Y., Morel, G., Reggiani, P., Bellini, M., regulation of the glucocorticoid receptor in the rat pituitary. Endo- Goya, R., 2006a. The neuroendocrine system as a model to evaluate crinology 120, 1558–1562.
experimental gene therapy. Current Gene Therapy 6, 125–129.
Asa, S., Ezzat, S., 1998. The cytogenesis and pathogenesis of pituitary Heren˜u´, C., Cristina, C., Rimoldi, O., Becu´-Villalobos, D., Cambiaggi, D., adenomas. Endocrinology Reviews 19, 798–827.
Portiansky, E., Goya, R., 2006b. Restorative effect of insulin-like Bevan, J.S., Webster, J., Burke, C.W., Scanlon, M.F., 1992. Dopamine growth factor-I gene therapy in the hypothalamus of senile rats with agonists and pituitary tumor shrinkage. Endocrinology Review 13, dopaminergic dysfunction. Gene Therapy 13, 1–9.
Hofmann, B., Fahlbusch, R., 2006. Treatment of Cushing's disease: a Boscaro, M., Barzon, L., Fallo, F., Sonino, N., 2001. Cushing's syndrome.
retrospective clinical study of the latest 100 cases. Frontiers Hormone The Lancet 357, 783–790.
Research 34, 158–184.
Bosje, J., Rijnberk, A., Mol, J., Voorhout, G., Kooistra, H., 2002. Plasma Karl, M., von Wichert, G., Kempter, E., Katz, D., Reincke, M., Monig, concentrations of ACTH precursors correlate with pituitary size and H., Ali, I., Stratakis, C., Oldfield, E., Chouros, G., Schulte, H., 1996.
resistance to dexamethasone in dogs with pituitary-dependent hyper- Nelson's syndorme associated with somatic frame shift mutation in the adrenocorticism. Domestic Animal Endocrinology 22, 201–210.
glucocorticoid receptor gene. Journal Clinical Endocrinology Metab- Bruyette, D.S., 1995. Canine pituitary-dependent hyperadrenocorticism: a olism 81, 124–129.
spontaneous animal model for neurodegenerative disorders and their Kemppainen, R.J., Zenoble, R.D., 1985. Non-dexametasone-suppressible, treatment with L-deprenyl. In: P. Yu, K. Tipton, A. Boulton, (Eds.), pituitary-dependent hyperadrenocorticism in dog. Journal American Current Neurochemical and pharmacological aspects of biogenic Veterinary Medical Association 187, 276–280.
amines, Progres in Brain Research, vol. 106, pp. 207–215.
Kemppainen, R.J., Zerbe, C.A., Sartin, J.L., 1989. Regulation and Caron, M.G., Beaulieu, M., Raymond, V., Gagne, B., Drouin, J., secretion of proopiomelanocortin peptides from isolated perifused Lefkowitz, R.J., Labrie, F., 1978. Dopaminergic receptors in the dog pituitary pars intermedia cells. Endocrinology 124, 2208–2217.
anterior pituitary gland. Journal Biololy Chemistry 253, 2244–2253.
Kintzer, P., Peterson, M., 1991. Mitotane (o,p0-DDD) treatment of 200 Castillo, V.A., Lalia, J.C., Casal, J., Casal, G., Esarte, M., Mira, G., dogs with pituitary- dependent hyperadrenocorticism. Journal Veter- Rodriguez, M., Marquez, A., 1996. Aminoglutetimide: alternativa inary Internal Medicine 5, 182–190.
terape´utica en caninos con Enfermedad de Cushing (hipo´fiso-depen- Komanicky, P., Spark, R.F., Melby, J.C., 1978. Treatment of Cushing's diente). Avances en Medicina Veterinaria 11, 93–96.
syndrome with trilostane (WIN 24,540), an inhibitor of adrenal steroid Castillo, V.A., Giacomini, D.P., Pa´ez-Pered, M., Stalla, J., Labeur, M., biosynthesis. Journal Clinical Endocrinology and Metabolism 47, Theodoropoulou, M., Holsboer, F., Grossman, A., Stalla, G., Arzt, E., V.A. Castillo et al. / Research in Veterinary Science 85 (2008) 26–34 Kooistra, H., Voorhout, G., Mol, J., Rijnberk, A., 1997. Correalation and Cushing's syndrome: basal concentrations. Endocrinology 119, between impairment of glucocorticoid feedback and the size of the pituitary gland in dogs with pituitary-dependent hyperadrenocortic- Petrossians, P., Ronci, N., Valdes Socin, H., Kalife, A., Stevenaert, A., ism. Journal of Endocrinology 152, 387–394.
Bloch, B., Tabarin, A., Beckers, A., 2001. ACTH silent adenoma Labeur, M., Arzt, E., Stalla, G., Pa´ez-Pereda, M., 2004. New perspective shrinking under cabergoline. European Journal Endocrinology 144, in the treatment of Cushing's syndrome. Current Drug Targets- Immune, Endocrine and Metabolic Disorders 4, 29–36.
Pivonello, R., Faggiano, A., Di Salle, F., Filipella, M., Lombardi, G., Lado-Abeal, J., Rodriguez-Arnao, J., Newell-Price, J.D., Perry, L.A., Colao, A., 1999. Complete remission of Nelson's syndrome after Grossman, A.B., Besser, G.M., Trainer, P.J., 1998. Menstrual abnor- 1-year treatment with cabergoline. Journal Endocrinology Investiga- malities in women with Cushing's disease are correlated with hyper- tion 22, 860–865.
cortisolemia rather than raised circulating androgen levels. Journal Pivonello, R., Ferone, D., de Herder, W., Kros, J., del Basso de Caro, M., Clinical Endocrinology Metabolism 83, 3083–3088.
Arvigo, M., Annunziato, L., Lombardi, G., Colao, A., Hofland, L., Lamberts, S., McLoad, R., 1990. Regulation of prolactin secretion at the Lamberts, S., 2004. Dopamine receptor expression and function in level of the lactotroph. Physiology Review 70, 279–318.
corticotroph pituitary tumors. Journal Clinical Endocrinology and Laurent, V., Kimble, A., Peng, B., Zhu, P., Pintar, J., Steiner, D., Metabolism 89, 2452–2462.
Lindberg, I., 2002. Mortality in 7B2 null mice can be rescued by Rijnberk, A., Mol, J., Kwant, M., Croughs, R., 1988a. Efects of adrenalectomy: involvement of dopamine in ACTH hypersecretion.
bromocriptine on corticotrophin, melanotrophin and corticosteroid Medical Sciences 99, 3087–3092.
secretion in dogs with pituitary-dependent hyperadrenocorticism.
Levy, A., Lightman, S., 2003. Molecular defects in the pathogenesis of Journal of Endocrinology 118, 271–277.
pituitary tumours. Frontiers in Neuroendocrinology 24, 94–127.
Rijnberk, A., Van Wees, A., Mol, J., 1988b. Assessment of two tests for Ling, G., Stabenfeldt, G., Comer, K., Gribble, D., Schechter, R., 1979.
the diagnosis of canine hyperadrenocorticism. Veterinary Research Canine hyperadrenocorticism: pre-treatment clinical and laboratory 122, 178–180.
evaluation of 117 cases. Journal American Veterinary Medical Rothulzen, J., 1991. Aging and the hypothalamus-pituitary-adrenocortical Association 174, 1211–1215.
axis, with special referente to tje dog. Acta Endocrinological 125, 73– Meij, B., Mol, J., Bevers, M., Rijnberk, A., 1997. Alterations in anterior pituitary function of dogs with pituitary-dependent hyperadrenocor- Saiardi, A., Bozzi, Y., Ja-Hyun Baik, J., Borrelli, E., 1997. Antiprolifer- ticism. Journal of Endocrinology 154, 505–512.
ative role of dopamine: loss of D2 receptors causes hormonal Meij, B., Voorhout, G., Rijnberk, A., 2002. Progress in transsphenoidal dysfunction and pituitary hyperplasia. Neuron 19, 115–126.
hypophysectomy for treatment of pituitary- dependent hyperadreno- Shraga-Slutzky, I., Shimon, H., Weinshtein, R., 2006. Clinical and corticism in dogs and cats. Molecular Cellular Endocrinology 197, 89– biochemical stabilization of Nelson's syndrome with long-term low- dose cabergoline treatment. Pituitary 9, 151–154.
Melmed, S., 2003. Mechanisms for pituitary tumorigenesis: the plastic Sieber-Ruckstuhl, N., Boretti, F., Wenger, M., Maser-Gluth, C., Reusch, pituitary. Journal Clinical Investigation 112, 1603–1618.
C., 2006. Cortisol, aldosterone, cortisol precursor, androgen and Mercado-Asis, L.B., Yasuda, K., Murayama, M., Mune, T., Morita, H., endogenous ACTH concentrations in dogs with pituitary-dependant Miura, K., 1992. Beneficial effects of high daily dose bromocriptine in hyperadrenocorticism treated with trilostane. Domestic Animal Endo- Cushing's disease. Endocrinology Japan 39, 385–395.
crinology 31, 63–75.
Middleton, D., Rijnberk, A., Bevers, M., Goos, H., Beeftink, E., Sonino, N., Boscaro, M., 1999. Medical therapy for Cushing's disease.
Thijssen, J., Croughs, R., 1987. Some functional and morpho- Endocrinology Metabolism Clinics North America 28, 211–222.
Speert, D., McClennen, S., Seasholtz, A., 2002. Sexually dimorphic Research 17, 10–17.
expression of corticotropin- releasing hormone-binding protein in the Missale, C., Nash, S., Robinson, S., Jaber, M., Caron, M., 1998.
mouse pituitary. Endocrinology 143, 4730–4741.
Dopamine receptors: from structure to function. Physiology Review Tanaka, S., 2003. Comparative aspects of intracellular proteolytic 78, 189–225.
processing of peptide hormone precursors: studies of proopiomelano- Munemura, M., Cote, T., Tsuruta, K., Eskay, R., Kebabian, J., 1980. The cortine processing. Zoological Science 20, 1183–1198.
dopamine receptor in the intermediate lobe of the rat anterior pituitary Thapar, H., Kovacs, K., Laws, E., Muller, P., 1993. Pituitary adenomas: gland: pharmacological characterization. Endocrinology 106, 1676– current concepts in classification, histopathology and molecular biology. The Endocrinologist 3, 39–57.
Ooi, G., Tawadros, N., Escalona, R., 2004. Pituitary cell lines and their Van Craenenbroeck, K., De Bosscher, K., Berghe, W., Vanhoenacker, P., endocrine applications. Molecular and Cellular Endocrinology 228, Haegeman, G., 2005. Role of glucocorticoids in dopamine-related neuropsychiatric disorders. Molecular and Cellular Endocrinology Pa´ez-Pareda, M., Kovalovsky, D., Hopfner, U., Theodoropoulou, M., 245, 10–22.
Pagotto, U., Uhl, E., Losa, M., Stalla, J., Gru¨bler, Y., Missale, C., Verhelst, J., Abs, R., Maiter, D., Van den Bruel, A., Vandeweghe, M., Arzt, E., Stalla, G., 2001. Retinoic acid prevents experimental Cushing Velkeniers, B., et al., 1999. Cabergoline in the treatment of hyper- syndrome. Journal Clinical Investigation 108, 1123–1131.
prolactinemia: a study in 455 patients. Journal of Clinical Endocri- Paez-Pereda, M., Artz, E., Stalla, G., 2002. Cushing's syndrome: drug nology and Metabolism 842, 518–522.
targets and therapeutic options. Experimental Opinion Therapy Westphal, C., Muller, L., Zhou, A., Zhu, X., Bonner-Weir, S., Schamb- Patents 12, 1537–1546.
elan, M., Steiner, D., Lindberg, I., Leder, P., 1999. The neuroendo- Peterson, M., Krieger, D., Drucker, W., Halmi, N., 1982. Immunocyto- crine protein 7B2 is required for peptide hormone processing in vivo chemical study of the hypophysis in 25 dogs with pituitary-dependent and provides a novel mechanism for pituitary Cushing's disease. Cell hyperadrenocorticism. Acta Endocrinological 101, 15–24.
96, 689–700.
Peterson, M., Orth, D., Halmi, N., Zielinski, A., Davis, D., Chavez, F., Young, E., Abelson, J., Lightman, S., 2004. Cortisol pulsatility and its role Drucker, W., 1986. Plasma immunoreactive proopiomelanocortin in stress regulation and health. Frontiers in Neuroendocrinology 25, peptides and cortisol in normal dogs and dogs with Addison's disease

Source: http://betpharm.com/downloads/cushingscastillo2008.pdf