Effects of trilostane on the pituitary-adrenocortical and renin-aldosterone axis in dogs with pituitary-dependent hypercortisolism

Association between post-ACTH cortisol and trilostane dosage in dogs with pituitary-dependent hypercortisolism

Trilostane is the current treatment of choice for managing pituitary-dependent hypercortisolism (PDH) in dogs. While prescribing higher initial doses may elevate the risk of iatrogenic hypocortisolism, opting for more conservative approach could result in delayed disease control, since most individuals end up requiring dosage increases. The adrenocorticotrophin stimulation test (ACTHst), a widely recognized hormonal test for assessing adrenal function, is an essential tool for monitoring the pharmacological treatment of canine hypercortisolism (CH) that can also be used for diagnostic purposes. The aim of this study was to investigate the relationship between post-ACTH cortisol (cpACTH) at PDH diagnosis and the required trilostane dose for sign control and endogenous cortisol regulation in dogs, considering a hypothesis that higher serum cpACTH concentration would necessitate a higher trilostane dosage for disease management. Data for 43 dogs with PDH had their diagnostic cpACTH recorded and correlated to the trilostane dosage necessary to control clinical signs and achieve satisfactory cortisol levels (ideally 2-7 μg/dL). The odds ratio (p=0.042) suggests that dogs with cpACTH ≥ 27 μg/dL at diagnosis are 96% more likely to need a higher trilostane dosage for achieving satisfactory control of PDH. Thus, cpACTH was found to be associated with the final trilostane dose for controlling PDH in dogs.

Iatrogenic symptomatic hypoadrenocorticism after treatment with trilostane for hyperadrenocorticism in dogs: eight cases (2008-2019)

OBJECTIVES

Trilostane is the medical treatment of choice for hyperadrenocorticism. Iatrogenic hypoadrenocorticism is thought to be rare, with most cases being transient and only a few cases of permanent hypoadrenocorticism have been reported. This study reports findings from eight cases of iatrogenic hypoadrenocorticism and examines the presence of concurrent diseases at the time of diagnosis.

MATERIALS AND METHODS

Medical records of dogs treated for hyperadrenocorticism with trilostane since 2008 were reviewed, and cases of clinical iatrogenic hypoadrenocorticism were extracted. Cases were considered permanent if long-term replacement therapy was required.

RESULTS

Eight dogs met the inclusion criteria. The time between the beginning of trilostane treatment and the diagnosis of hypoadrenocorticism ranged from 4 days to 13 months, and the dosage of trilostane ranged between 1 and 8 mg/kg/day. Six dogs had a suspicion of concurrent disease at the time of hypoadrenocorticism diagnosis. The trilostane dose was decreased in two dogs; trilostane was withdrawn in one case without further relapse of hyperadrenocorticism; and glucocorticoids with or without mineralocorticoid supplementation were prescribed in five dogs. Two of these five dogs were lost to follow-up, and the other three had a diagnosis of permanent hypoadrenocorticism. Adrenal gland ultrasonography in these three dogs showed a progressive reduction in gland sizes with heterogeneous echogenicity.

CLINICAL SIGNIFICANCE

Iatrogenic hypoadrenocorticism is a rare but potentially life-threatening complication of trilostane treatment in dogs with hyperadrenocorticism. The occurrence of a concurrent disease might trigger the development of clinical signs of hypoadrenocorticism in previously subclinical dogs.

The Efficacy of a 3β-Hydroxysteroid Dehydrogenase Inhibitor for the Termination of Mid-Term Pregnancies in Dogs

Simple Summary

The medical termination of unwanted pregnancies in dogs is practiced throughout the world for many reasons, including at the request of animal owners. For these procedures, it is advised to use rapidly effective drugs with minimal side effects. In this study, we investigated trilostane, which decreases progesterone levels, for its efficacy in terminating mid-term pregnancies in dogs, as well as potential side effects. Although trilostane is not a standalone alternative for the termination of pregnancy in dogs, it has been determined that its combined use with another medical agent of known efficacy reduces both the abortion time and potential side effects. Further studies investigating an increased frequency of administration rather than the administration dose could contribute to determining the efficacy of trilostane in dogs.

Abstract

Progesterone (P4) is the only hormone needed to maintain pregnancy in dogs. Therefore, a competitive inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) could be a safe and effective option to terminate pregnancy by inhibiting P4 synthesis. To address this hypothesis, we investigated the efficacy of trilostane (TRL), a competitive inhibitor of 3β-HSD, in terminating pregnancy in dogs. Twenty-one dogs between days 30 and 38 of pregnancy were randomly assigned to one of two treatment groups (trilostane (TRL) and aglepristone (AGL)) and an untreated control (CON) group (n = 7 dogs each). Fetal heart rates (FHRs) (measured at 12 h intervals) and serum P4 concentrations (measured at 6 h intervals) were evaluated. The pregnancy termination rates were 0% and 100% in the TRL and AGL groups, respectively. The decrease in the FHR in the TRL and AGL groups was significantly lower than that observed in the CON group. There was a marked decrease in P4 concentrations in the TRL group 6, 54, and 102 h after the initiation of treatment. The luteal expression of StAR appeared to be weaker in the AGL group than the CON group. In conclusion, although a treatment-induced decrease was observed in plasma P4 concentrations, a seven-day TRL treatment alone was not effective in terminating pregnancies. Further studies are needed on the effects of the prolonged administration of TRL with varying doses and frequencies for the termination of mid-term pregnancy in dogs.

Association between ACTH stimulation test results and clinical signs in dogs with hyperadrenocorticism treated with trilostane

Trilostane is the recommended medical treatment for dogs with hyperadrenocorticicm (HAC). The objective of this study was to investigate the association between ACTH stimulation test (ACTHST) results, and relevant clinical signs, in dogs treated with trilostane. A disease-specific questionnaire was developed, which included the owner's assessment of polydipsia, polyuria, polyphagia, panting, and satisfaction with the treatment, based on a 5-response category rating scale. Forty-nine dogs with HAC were prospectively enrolled. Dogs were grouped according to their recheck appointment (first recheck, 710 days after commencement of treatment or change of trilostane dose; second recheck, 4 weeks after the first recheck; third recheck, performed at 3-6 months intervals once the dog was well controlled). At the recheck appointment, the owner's questionnaire responses were recorded, and an ACTHST was performed, along with urine specific gravity measurement. Linear mixed effects models were used to assess differences among the three recheck time points and to test possible associations between ACTHST results and clinical signs. Significant differences between rechecks were present for stimulated cortisol (first to third recheck, P < 0.001; second to third recheck, P < 0.01), polydipsia (first to second recheck, P = 0.001), polyuria (first to second recheck, P < 0.001; first to third recheck, P = 0.001), and owner satisfaction (first to second recheck, P < 0.001; first to third recheck, P < 0.001). Backward stepwise variable elimination did not identify any significant associations between ACTHST results and clinical signs. Therefore, clinical signs of HAC were not predicted based on the ACTHST results.

Evaluation of Iatrogenic Hypocortisolemia Following Trilostane Therapy in 48 Dogs with Pituitary-Dependent Hyperadrenocorticism

This study aimed to retrospectively describe the clinical progression following diagnosis of iatrogenic hypocortisolemia (iHC) in 48 dogs receiving trilostane for pituitary-dependent hyperadrenocorticism. Cortisol concentrations were ≥1.5 mg/dL within 6 mo following diagnosis of iHC in 76.3% of dogs (95% confidence interval [CI] 59.8-88.6%). At the time of study completion, 25% of dogs (95% CI 13.6-39.6%) were receiving either glucocorticoids or mineralocorticoids or both; 42% of dogs (95% CI 27.6-56.8%) were on no adrenal-related medications; and the remaining 33% of dogs (95% CI 20.4-48.4%) were receiving trilostane. No patient-, clinicopathologic-, or trilostane-associated factors were identified to influence adrenal recovery following diagnosis of iHC, and it remains difficult to predict the clinical progression in this population of dogs.

Concurrent pituitary and adrenocortical lesions on computed tomography imaging in dogs with spontaneous hypercortisolism

Background

Spontaneous hypercortisolism or Cushing's syndrome in dogs is either pituitary or adrenal dependent, but concurrent pituitary and adrenal hypercortisolism also has been reported.

Objective

To determine how often concurrent pituitary and adrenal lesions are present in dogs with spontaneous hypercortisolism.

Animals

Two hundred one client‐owned dogs with spontaneous hypercortisolism.

Methods

Retrospective study. Pre‐ and post‐contrast computed tomography (CT) scans of the pituitary and adrenal glands were performed in dogs with confirmed hypercortisolism.

Results

In dogs with dexamethasone‐suppressible hypercortisolism (122/201), 78 dogs (64%) had an enlarged pituitary gland (median pituitary height/brain area [P/B], 0.43 × 10⁻² mm⁻¹; range, 0.32‐1.21 × 10⁻² mm⁻¹). Two of these 78 dogs had concurrent adrenal lesions. In the remaining dogs (44/122; 36%), the pituitary gland was not enlarged. In the dexamethasone‐resistant group (79/201), the pituitary gland was enlarged in 47 dogs (59%; median P/B, 0.57 × 10⁻²; range, 0.32‐1.50 × 10⁻² mm⁻¹). Eight of these 47 dogs (17%) had concurrent adrenal lesions. In the remaining 32 dexamethasone‐resistant dogs (41%), the pituitary gland was not enlarged. Among them, 27 dogs had adrenal lesions and suppressed ACTH concentrations consistent with adrenal‐dependent hypercortisolism and 5 dogs were diagnosed with pituitary‐dependent hypercortisolism.

Conclusions and Clinical Importance

Concurrent pituitary and adrenal lesions were present in 5% of all dogs with hypercortisolism and in 10% of the dexamethasone‐resistant dogs. Diagnostic imaging of both pituitary and adrenal glands should be included in the diagnostic evaluation of every dog with spontaneous hypercortisolism to obtain information needed for estimation of prognosis and choosing the optimal treatment.

Melanocortin 2 receptor antagonists in canine pituitary-dependent hypercortisolism: in vitro studies

Canine hypercortisolism is most often caused by an ACTH-secreting pituitary adenoma (pituitary-dependent hypercortisolism; PDH). An interesting target for a selective medical treatment of PDH would be the receptor for ACTH: the melanocortin 2 receptor (MC2R). In this study we investigated whether two peptide compounds, BIM-22776 (#776) and BIM-22A299 (#299), are effective MC2R antagonists in vitro. Their effects on cortisol production and mRNA expression of steroidogenic enzymes, MC2R and melanocortin 2 receptor accessory protein (MRAP) were evaluated in primary adrenocortical cell cultures (n = 8) of normal canine adrenal glands. Cortisol production stimulated by 50 nM ACTH was dose-dependently inhibited by #299 (inhibition 90.7 ± 2.3% at 5 μM) and by #776 (inhibition 38.0 ± 5.2% at 5 μM). The ACTH-stimulated mRNA expression of steroidogenic enzymes, MC2R and MRAP was significantly inhibited by both compounds, but most potently by #299. These results indicate that canine primary cell culture is a valuable in vitro system to test MC2R antagonists, and that these compounds, but especially #299, are effective MC2R antagonists in vitro. To determine its efficacy in vivo, further studies are warranted. Antagonism of the MC2R is a promising potential treatment approach in canine PDH.

Treating canine Cushing's syndrome: Current options and future prospects

Naturally occurring hypercortisolism, also known as Cushing's syndrome, is a common endocrine disorder in dogs that can be caused by an adenocorticotrophic hormone (ACTH)-producing pituitary adenoma (pituitary-dependent hypercortisolism, PDH; 80-85% of cases), or by an adrenocortical tumor (ACT; 15-20% of cases). To determine the optimal treatment strategy, differentiating between these two main causes is essential. Good treatment options are surgical removal of the causal tumor, i.e. hypophysectomy for PDH and adrenalectomy for an ACT, or radiotherapy in cases with PDH. Because these options are not without risks, not widely available and not suitable for every patient, pharmacotherapy is often used. In cases with PDH, the steroidogenesis inhibitor trilostane is most often used. In cases with an ACT, either trilostane or the adrenocorticolytic drug mitotane can be used. Although mostly effective, both treatments have disadvantages. This review discusses the current treatment options for canine hypercortisolism, and considers their mechanism of action, efficacy, adverse effects, and effect on survival. In addition, developments in both adrenal-targeting and pituitary-targeting drugs that have the potential to become future treatment options are discussed, as a more selective and preferably also tumor-targeted approach could have many advantages for both PDH and ACTs.

Steroidogenic factor-1 inverse agonists as a treatment option for canine hypercortisolism: in vitro study

Hypercortisolism is one of the most commonly diagnosed endocrinopathies in dogs, and new targeted medical treatment options are desirable. Steroidogenic factor-1 (SF-1), an orphan nuclear hormone receptor, is a key regulator of adrenal steroidogenesis, development, and growth. In pituitary-dependent hypercortisolism (PDH), high plasma ACTH concentrations increase the transcriptional activity of SF-1. In adrenal-dependent hypercortisolism, SF-1 expression is significantly greater in dogs with recurrence after adrenalectomy than in those without recurrence. Inhibition of SF-1 could therefore be an interesting treatment option in canine spontaneous hypercortisolism. We determined the effects of 3 SF-1 inverse agonists, compounds IsoQ A, #31, and #32, on cortisol production, on the messenger RNA (mRNA) expression of steroidogenic enzymes and SFs, and on cell viability, in primary adrenocortical cell cultures of 8 normal adrenal glands and of 3 cortisol-secreting adrenocortical tumors (ATs). To mimic PDH, the normal adrenocortical cell cultures were stimulated with ACTH. The results show that only compound #31 inhibited cortisol production and SF-1 target gene expression in non-ACTH-stimulated and ACTH-stimulated normal adrenocortical cells but did not affect cell viability. In the AT cell cultures, the effects of #31 on cortisol production and target gene expression were variable, possibly caused by a difference in the SF-1 mRNA expressions of the primary tumors. In conclusion, inhibition of SF-1 activity shows much promise as a future treatment for canine hypercortisolism.

Proopiomelanocortin processing and prohormone convertase 1 level in dogs with pituitary corticotroph tumors

Preliminary data suggest that prohormone convertase 1 (PC1/3) protein expression and proopiomelanocortin (POMC) processing are altered in large corticotroph tumors. The aim of this study was to characterize the levels of ACTH precursors and PC1/3 protein in small and large corticotroph tumors of dogs with Cushing's disease. Pituitary tumors of dogs with Cushing's disease were collected postmortem 30 min to 12h after natural death or euthanasia, and classified as small or large. POMC, pro-ACTH, and PC1/3 were detected by Western blotting. Five small and 6 large corticotroph tumors were collected. POMC and pro-ACTH signals were visualized in 5/6 large tumors and in 4/5 small tumors. The strongest signal intensity was observed in 2 large tumors. The PC1/3 signal was weak to undetectable in 6/6 large tumors but strong in 5/5 small tumors. These results suggest differences in PC1/3 protein levels and patterns of POMC processing between large and small corticotroph tumors. If confirmed in larger groups of tumors, further studies will be required to characterize the mechanism involved in these differences.

Pre-trilostane and three-hour post-trilostane cortisol to monitor trilostane therapy in dogs

It is recommended that trilostane therapy of canine hyperadrenocorticism is monitored using an ACTH stimulation test, however this has never been validated. Three cortisol concentrations (pre-trilostane, 3-hour posttrilostane and 1-hour post-ACTH stimulation) were compared to a clinical score obtained from an owner questionnaire. There were 110 sets of 3 cortisol measurements and questionnaires obtained from 67 trilostane treated dogs. Questionnaire results were used to classify each dog as well or unwell. Well dogs were then categorised as having excellent, moderate or poor hyperadrenocorticism control, using thresholds produced by 14 independent veterinarians. Correlation co-efficients were used to compare the three cortisol concentrations to the owner score and the Kruskal Wallis and Mann-Whitney U tests were used to compare the three cortisol concentrations between categories of control. Cortisol cut-off values between significantly different categories were determined using ROC curves. Pre-trilostane and 3-hour post-trilostane cortisol were better correlated to the owner score and had cut-offs to differentiate between categories of control that had superior sensitivity and specificity results, than the post-ACTH cortisol. Iatrogenic hypoadrenocorticism was not detected in any unwell dog. This study shows that the pre-trilostane and 3-hour post-trilostane cortisol are potentially better monitoring methods than the ACTH stimulation test.

Evaluation of baseline cortisol concentration to monitor efficacy of twice-daily administration of trilostane to dogs with pituitary-dependent hyperadrenocorticism: 22 cases (2008-2012)

OBJECTIVE

To evaluate use of cortisol concentration prior to ACTH stimulation (baseline) to monitor efficacy of twice-daily administration of trilostane to dogs with pituitary-dependent hyperadrenocorticism (PDH).

DESIGN

Retrospective case series.

ANIMALS

22 dogs with PDH.

PROCEDURES

The database of a veterinary hospital was searched to identify dogs with PDH that were treated with the FDA-approved veterinary formulation of trilostane twice daily between January 1, 2008, and December 31, 2012. For each dog, signalment and details regarding each hospital visit including comorbidities, electrolyte concentrations, and clinical signs were extracted from the record. For each ACTH stimulation test performed, the respective correlations between baseline cortisol concentration and the cortisol concentration after ACTH stimulation (ACTH-stimulated cortisol concentration) and resultant decision regarding trilostane dose adjustment were determined. Excessive suppression of cortisol production was defined as an ACTH-stimulated cortisol concentration < 2.0 μg/dL. The ability of various baseline cortisol concentrations to predict whether a dog had excessive suppression of cortisol production was determined.

RESULTS

109 ACTH stimulation tests were performed for the 22 dogs. A baseline cortisol concentration > 3.2 μg/dL predicted that ACTH-stimulated cortisol concentration would be ≥ 2.0 μg/dL with 100% certainty; however, 14 of 64 tests with a baseline cortisol concentration > 3.2 μg/dL had an ACTH-stimulated cortisol concentration ≤ 3.2 μg/dL, which was suggestive of inadequate adrenocortical cortisol reserves.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that baseline cortisol concentration should not be used as the sole monitoring tool for management of dogs with PDH treated with trilostane twice daily.

Comparison of adrenocorticotropic hormone stimulation test results started 2 versus 4 hours after trilostane administration in dogs with naturally occurring hyperadrenocorticism

Background

Trilostane medical treatment of naturally occurring hyperadrenocorticism (NOH) in dogs is common, as is use of the adrenocorticotropic hormone (ACTH) stimulation test (ACTHst) in monitoring response to treatment. There is uncertainty regarding when the ACTHst should be started relative to time of trilostane administration.

Objective

To compare ACTHst results in dogs being treated for NOH with trilostane when the test is begun 2 versus 4 hours after trilostane administration.

Animals

Twenty‐one privately owned dogs with NOH, each treated with trilostane for at least 30 days.

Methods

Each dog had 2 ACTHst completed, 1 started 2 hours and the other 4 hours after trilostane administration. The second test was started no sooner than 46 hours and no later than 74 hours after the first.

Results

For all 21 dogs, the mean post‐ACTH serum cortisol concentration from tests started 2 hours after trilostane administration (5.4 ± 3.7 μg/dL) was significantly lower (P = .03) as compared with results from the tests started 4 hours after administration (6.5 ± 4.5 μg/dL).

Conclusions

Results of ACTHst started at different times yield significantly different results. Dogs with NOH, treated with trilostane, and monitored with ACTHst results should have all of their subsequent ACTHst tests begun at or about the same time after trilostane administration.

Effect of trilostane and mitotane on aldosterone secretory reserve in dogs with pituitary-dependent hyperadrenocorticism

Background

Maximal aldosterone secretion in healthy dogs occurs 30 minutes postadrenocorticotropin (ACTH; 5 μg/kg IV) stimulation. The effect of trilostane and mitotane on aldosterone at that time is unknown.

Objectives

To assess the effect of trilostane and mitotane in dogs with pituitary‐dependent hyperadrenocorticism on aldosterone secretory reserve. To determine if aldosterone concentration correlates with electrolyte concentrations.

Animals

Serum collected from 79 client‐owned dogs and 33 stored samples.

Methods

Client‐owned dogs had ACTH stimulation tests with cortisol concentrations measured at 0 and 60 minutes and aldosterone concentrations measured at 0, 30, and 60 minutes. Stored samples had aldosterone concentrations measured at 0 and 60 minutes. Ten historical clinically healthy controls were included. All had basal sodium and potassium concentrations measured.

Results

The aldosterone concentrations in the mitotane‐ and trilostane‐treated dogs at 30 and 60 minutes post‐ACTH were significantly lower than in clinically healthy dogs; no significant difference was detected in aldosterone concentration between 30 and 60 minutes in treated dogs. However, a significantly higher percentage of dogs had decreased aldosterone secretory reserve detected at 30 minutes than at 60 minutes. At 30 minutes, decreased secretory reserve was detected in 49% and 78% of trilostane‐ and mitotane‐treated dogs, respectively. No correlation was detected between aldosterone and serum electrolyte concentrations.

Conclusions and Clinical Importance

Decreased aldosterone secretory reserve is common in trilostane‐ and mitotane‐treated dogs; it cannot be predicted by measurement of serum electrolyte concentrations. Aldosterone concentration at 30 minutes post‐ACTH stimulation identifies more dogs with decreased aldosterone secretory reserve than conventional testing at 60 minutes.

Effect of trilostane on hormone and serum electrolyte concentrations in dogs with pituitary-dependent hyperadrenocorticism

Background

The effects of trilostane on key hormones and electrolytes over 24 hours in dogs with pituitary‐dependent hyperadrenocorticism (PDH) are unknown.

Objectives

To determine the plasma concentration of cortisol, endogenous adrenocorticotropic hormone (ACTH), aldosterone, sodium, potassium, and ionized calcium concentrations, and plasma renin activity over a 24‐hour period after administration of trilostane to dogs with well‐controlled PDH.

Animals

Nine dogs (mean age 9.3 ± 0.67 years, mean weight 31.9 ± 6.4 kg) with confirmed PDH.

Methods

Prospective study. Thirty days after the first administration of trilostane, blood samples were taken at −30, 0 (baseline), 15, 30, 60, and 90 minutes, and 2, 3, 4, 6, 8, 12, 16, 20, and 24 hours after administration of trilostane and plasma concentration of cortisol, endogenous ACTH, aldosterone, sodium, potassium, ionized calcium, and renin activity were determined.

Results

Cortisol concentrations decreased significantly (P < .001) 2–4 hours after trilostane administration. From baseline, there was a significant (P < .001) increase in endogenous ACTH concentrations between hours 3–12, a significant increase (P < .001) in aldosterone concentration between hours 16–20, and a significant (P < .001) increase in renin activity between hours 6–20. Potassium concentration decreased significantly (P < .05) between hours 0.5–2.

Conclusion and Clinical Importance

Treatment with trilostane did not cause clinically relevant alterations in plasma aldosterone and potassium concentration. Results suggest that in dogs with PDH, the optimal time point for an ACTH‐stimulation test to be performed is 2–4 hours after trilostane dosing. Future studies are necessary to establish interpretation criteria for a 2‐ to 4‐hour postpill ACTH‐stimulation test.

Evaluation of baseline cortisol, endogenous ACTH, and cortisol/ACTH ratio to monitor trilostane treatment in dogs with pituitary-dependent hypercortisolism

BACKGROUND

The effectiveness of trilostane treatment is currently monitored by regular ACTH stimulation tests, which are time-consuming and expensive. Therefore, a monitoring system without a stimulation protocol and with less client expense would be preferable.

HYPOTHESIS/OBJECTIVES

The aim of our study was to evaluate if baseline cortisol, endogenous ACTH (ACTH) concentration or the baseline cortisol to ACTH ratio (cortisol/ACTH ratio) could replace the ACTH stimulation test.

ANIMALS

Forty trilostane-treated dogs with pituitary-dependent hypercortisolism (PDH) were included in this prospective study.

METHODS

A total of 148 ACTH stimulation tests and 77 ACTH concentrations and cortisol/ACTH ratios were analyzed. Control of cortisol release was classified according to cortisol concentration after ACTH administration as excessive (<1.5 μg/dL; group 1), adequate (1.5-5.4 μg/dL; group 2), or inadequate (>5.4 μg/dL; group 3).

RESULTS

Baseline cortisol concentrations had considerable overlap between excessively, adequately, and inadequately controlled dogs. Only baseline cortisol >4.4 μg/dL (in 12% of tests) was a reliable diagnosis of inadequate control. Endogenous ACTH concentrations did not differ between groups. The overlap of the cortisol/ACTH ratio between groups was large. Correct classification was only possible if the cortisol/ACTH ratio was >15, which occurred in 4% of tests.

CONCLUSIONS AND CLINICAL IMPORTANCE

To monitor trilostane treatment the ACTH stimulation test cannot be replaced by baseline cortisol, ACTH concentration, or the cortisol/ACTH ratio.

Animal models of adrenocortical tumorigenesis

Over the past decade, research on human adrenocortical neoplasia has been dominated by gene expression profiling of tumor specimens and by analysis of genetic disorders associated with a predisposition to these tumors. Although these studies have identified key genes and associated signaling pathways that are dysregulated in adrenocortical neoplasms, the molecular events accounting for the frequent occurrence of benign tumors and low rate of malignant transformation remain unknown. Moreover, the prognosis for patients with adrenocortical carcinoma remains poor, so new medical treatments are needed. Naturally occurring and genetically engineered animal models afford a means to investigate adrenocortical tumorigenesis and to develop novel therapeutics. This comparative review highlights adrenocortical tumor models useful for either mechanistic studies or preclinical testing. Three model species - mouse, ferret, and dog - are reviewed, and their relevance to adrenocortical tumors in humans is discussed.

Long-term follow-up of renal function in dogs after treatment for ACTH-dependent hyperadrenocorticism

BACKGROUND

Systemic hypertension and proteinuria are frequent complications in dogs with Cushing's syndrome and do not always resolve after treatment of hypercortisolism. Therefore, dogs with Cushing's syndrome may be at risk for renal dysfunction before and after treatment.

HYPOTHESIS/OBJECTIVES

To assess renal function in dogs with ACTH-dependent hyperadrenocorticism (ADHAC) before and after treatment.

ANIMALS

A total of 19 dogs with ADHAC and 12 control dogs.

METHODS

Renal function was assessed before and at 1, 3, 6, and 12 months after treatment. Twelve dogs were treated with trilostane and 7 dogs by transsphenoidal hypophysectomy. Routine renal markers were measured and urinary albumin (uALB), immunoglobulin G (uIgG), and retinol-binding protein (uRBP) were assessed by ELISA. Urinary N-acetyl-β-D-glucosaminidase (uNAG) was determined colorimetrically. All urinary markers were indexed to urinary creatinine concentration (c). Plasma clearance of creatinine (Cl(creat)), exo-iohexol (Cl(exo)), and endo-iohexol (Cl(endo)) was used to measure glomerular filtration rate (GFR). Data were analyzed using a general linear model.

RESULTS

Serum creatinine and urea concentrations increased post-treatment, but remained within reference ranges. Plasma Cl(creat) and Cl(endo) were significantly lower post-treatment, whereas Cl(exo) was not different. Urinary protein-to-creatinine ratio (UPC), uALB/c, uIgG/c, and uRBP/c were decreased post-treatment, but at 12 months 5/13 dogs remained proteinuric. Urinary NAG/c did not change significantly.

CONCLUSIONS AND CLINICAL IMPORTANCE

A decrease in GFR and persistent proteinuria post-treatment may warrant the clinician's attention. Future research including renal histopathology of dogs with persistent proteinuria or low GFR is needed to further assess renal outcome.

Adrenocorticotropic hormone, but not trilostane, causes severe adrenal hemorrhage, vacuolization, and apoptosis in rats

Adrenal necrosis has been reported as a complication of trilostane application in dogs with hyperadrenocorticism. One suspicion was that necrosis results from the increase of adrenocorticotropic hormone (ACTH) during trilostane therapy. The aim of the current study was to assess the effects of ACTH and trilostane on adrenal glands of rats. For experiment 1, 36 rats were divided into 6 groups. Groups 1.1 to 1.4 received ACTH in different doses (60, 40, 20, and 10 μg/d) infused subcutaneously with osmotic minipumps for 16 wk. Group 1.5 received saline, and group 1.6 received no therapy. For experiment 2, 24 rats were divided into 3 groups. Group 2.1 and 2.2 received 5 and 50 mg/kg trilostane/d orally mixed into chocolate pudding for 16 wk. Eight control rats received pudding alone. At the end of the experiments, adrenal glands were assessed for necrosis by histology and immunohistochemistry; levels of endogenous ACTH and nucleosomes were assessed in the blood. Rats treated with 60 μg ACTH/d showed more hemorrhage and vacuolization and increased numbers of apoptotic cells in the adrenal glands than rats treated with 20 or 10 μg ACTH/d, trilostane, or control rats. Rats treated with 60 μg ACTH/d had a higher amount of nucleosomes in the blood compared with rats treated with 10 μg ACTH/d, trilostane, or saline. We conclude that in healthy rats ACTH, but not trilostane, causes adrenal degeneration in a dose-dependent manner. Results of this study support the hypothesis that adrenal gland lesions seen in trilostane-treated dogs are caused by ACTH and not by trilostane.

A comparison of factors that influence survival in dogs with adrenal-dependent hyperadrenocorticism treated with mitotane or trilostane

BACKGROUND

Trilostane is a recognized treatment for canine pituitary-dependent hyperadrenocorticism (PDH); however, its efficacy in dogs with adrenal-dependent hyperadrenocorticism (ADH) is unknown.

OBJECTIVES

To examine factors that might influence survival in the medical management of ADH, with particular emphasis on treatment selection.

ANIMALS

Thirty-seven animals referred to 4 centers over a period of 12 years that had been diagnosed with ADH and treated with either trilostane (22/37), mitotane (13/37), or both (2/37).

METHODS

Retrospective analysis of clinical records.

RESULTS

There was no statistically significant difference between the survival times of 13 dogs treated only with mitotane when compared with 22 dogs treated only with trilostane. The median survival time for animals treated with trilostane was 353 days (95% confidence interval [CI] 95-528 days), whereas it was 102 days (95% CI 43-277 days) for mitotane. Metastatic disease was detected in 8 of 37 dogs. There was a significantly lower probability of survival for dogs with metastatic disease when compared with those without metastatic disease (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The choice of medical treatment for ADH may not have a major effect on survival times. However, the presence of metastatic disease considerably decreases survival time regardless of the choice of medical treatment.

Cushing's syndrome, glucocorticoids and the kidney

Glucocorticoids (GCs) affect renal development and function in fetal and mature kidneys both indirectly, by influencing the cardiovascular system, and directly, by their effects on glomerular and tubular function. Excess GCs due to endogenous GC overproduction in Cushing's syndrome or exogenous GC administration plays a pivotal role in hypertension and causes increased cardiac output, total peripheral resistance and renal blood flow. Glucocorticoids increase renal vascular resistance (RVR) in some species and experimental settings and decrease RVR in others. Short term administration of adrenocorticotrophic hormone or GCs causes an increased glomerular filtration rate (GFR) in humans, rats, sheep and dogs. Interestingly, chronic exposure may cause a decreased GFR in combination with a higher cardiovascular risk in human patients with Cushing's syndrome. Glomerular dysfunction leads to proteinuria and albuminuria in canine and human Cushing's patients, and some cases also show histological evidence of glomerulosclerosis. Tubular dysfunction is reflected by an impaired urinary concentrating ability and disturbed electrolyte handling, which can potentially result in increased sodium reabsorption, hypercalciuria and urolithiasis. Conversely, chronic kidney disease can also alter GC metabolism. More research needs to be performed to further evaluate the renal consequences of Cushing's syndrome because of its implications for therapeutic aspects as well as the general well-being of the patient. Because there is a high incidence of Cushing's syndrome in canines, which is similar to the syndrome in humans, dogs are an interesting animal model to investigate the link between hypercortisolism and renal function.