Hyperadrenocorticism in six cats

2022 Update of the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) Domain 1- Defining populations at risk

OBJECTIVES

To expand the number of conditions and interventions explored for their associations with thrombosis in the veterinary literature and to provide the basis for prescribing recommendations.

DESIGN

A population exposure comparison outcome format was used to represent patient, exposure, comparison, and outcome. Population Exposure Comparison Outcome questions were distributed to worksheet authors who performed comprehensive searches, summarized the evidence, and created guideline recommendations that were reviewed by domain chairs. The revised guidelines then underwent the Delphi survey process to reach consensus on the final guidelines. Diseases evaluated in this iteration included heartworm disease (dogs and cats), immune-mediated hemolytic anemia (cats), protein-losing nephropathy (cats), protein-losing enteropathy (dogs and cats), sepsis (cats), hyperadrenocorticism (cats), liver disease (dogs), congenital portosystemic shunts (dogs and cats) and the following interventions: IV catheters (dogs and cats), arterial catheters (dogs and cats), vascular access ports (dogs and cats), extracorporeal circuits (dogs and cats) and transvenous pacemakers (dogs and cats).

RESULTS

Of the diseases evaluated in this iteration, a high risk for thrombosis was defined as heartworm disease or protein-losing enteropathy. Low risk for thrombosis was defined as dogs with liver disease, cats with immune-mediated hemolytic anemia, protein-losing nephropathy, sepsis, or hyperadrenocorticism.

CONCLUSIONS

Associations with thrombosis are outlined for various conditions and interventions and provide the basis for management recommendations. Numerous knowledge gaps were identified that represent opportunities for future studies.

Feline comorbidities: Recognition, diagnosis and management of the cushingoid diabetic

PRACTICAL RELEVANCE

Diabetes mellitus (DM) is a common feline endocrinopathy, and is often driven by underlying insulin resistance with associated pancreatic beta (β)-cell dysfunction. Although spontaneous hyperadrenocorticism (HAC) with hypercortisolemia (hypercortisolism) is relatively uncommon in cats, it is a well-established cause of insulin resistance and is routinely associated with DM in this species.

CLINICAL CHALLENGES

Many of the clinical signs associated with feline HAC are subtle and may be attributed to concurrent DM or the aging process. Failure to recognize HAC in the diabetic cat can impact patient wellbeing and predispose the patient to progressive compromise. Unfortunately, it can be difficult to establish a diagnosis of HAC, as test results may be influenced by poor diabetic regulation, and protocols are different to those used in canine patients. Treatment options depend on the underlying cause, and often require careful, ongoing assessment and modulation of both adrenal function and insulin requirements. However, various approaches have been shown to either improve glycemic control in cats with sustained insulin dependence, or facilitate diabetic remission.

EVIDENCE BASE

This review summarizes the current literature on feline HAC, with a particular focus on cats with concurrent DM. The clinical findings that suggest HAC are discussed, along with an outline of diagnostic options and their limitations. Published outcomes for various medical options, surgical procedures and radiation therapy are provided. The authors also share their thoughts on the safe and effective management of cats with HAC and DM, with an emphasis on the anticipation and recognition of changing insulin requirements.

Feline abdominal ultrasonography: what's normal? what's abnormal? The adrenal glands

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Ultrasound examination of the adrenal glands can provide important information pertaining to several conditions including hyperaldosteronism and hyperadrenocorticism.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even for the experienced ultrasonographer, differentiating between incidental findings, such as adrenal mineralisation, and clinically significant pathological changes can be challenging.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses the ultrasonographic examination of the normal and diseased adrenal glands. Aimed at general practitioners who wish to improve their knowledge of and confidence in feline abdominal ultrasound, this review is accompanied by high-resolution images and videos available online as supplementary material.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although the use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Clinical, laboratory, and hemostatic findings in cats with naturally occurring sepsis

OBJECTIVE To characterize clinical and laboratory findings in cats with naturally occurring sepsis, emphasizing hemostasis-related findings, and evaluate these variables for associations with patient outcomes. DESIGN Prospective, observational, clinical study. ANIMALS 31 cats with sepsis and 33 healthy control cats. PROCEDURES Data collected included history; clinical signs; results of hematologic, serum biochemical, and hemostatic tests; diagnosis; and outcome (survival vs death during hospitalization or ≤ 30 days after hospital discharge). Differences between cats with and without sepsis and associations between variables of interest and death were analyzed statistically. RESULTS The sepsis group included cats with pyothorax (n = 10), septic peritonitis (7), panleukopenia virus infection (5), bite wounds (5), abscesses and diffuse cellulitis (3), and pyometra (1). Common clinical abnormalities included dehydration (21 cats), lethargy (21), anorexia (18), pale mucous membranes (15), and dullness (15). Numerous clinicopathologic abnormalities were identified in cats with sepsis; novel findings included metarubricytosis, hypertriglyceridemia, and high circulating muscle enzyme activities. Median activated partial thromboplastin time and plasma D-dimer concentrations were significantly higher, and total protein C and antithrombin activities were significantly lower, in the sepsis group than in healthy control cats. Disseminated intravascular coagulopathy was uncommon (4/22 [18%] cats with sepsis). None of the clinicopathologic abnormalities were significantly associated with death on multivariate analysis. CONCLUSIONS AND CLINICAL RELEVANCE Cats with sepsis had multiple hematologic, biochemical, and hemostatic abnormalities on hospital admission, including several findings suggestive of hemostatic derangement. Additional research including larger numbers of cats is needed to further investigate these findings and explore associations with outcome.

Peculiarities of feline hyperadrenocorticism: Update on diagnosis and treatment

Practical relevance: Hyperadrenocorticism (HAC) is a relatively uncommon endocrinopathy of older cats, with a mean age at diagnosis of 10 years. In addition to pituitary-dependent and adrenal-dependent hypercortisolism, clinical signs of HAC can result from adrenal sex steroid-producing tumours. Clinical challenges: While HAC in cats has many similarities to canine HAC, there are key differences in presentation, diagnosis and response to therapy. Most, but not all, cats with HAC have concurrent diabetes mellitus, which is often insulin resistant. Up to a third of cats with HAC have extreme skin fragility and are at high risk of debilitating iatrogenic skin tears during diagnostic or therapeutic interventions. Infections of the skin and nail beds, and urinary, respiratory and gastrointestinal tract, secondary to cortisol-induced immune suppression, are also common. Cats respond differently to dogs to adrenal function tests including adrenocorticotropic hormone (ACTH) stimulation and dexamethasone suppression tests; a 10-fold higher dose of dexamethasone is recommended in cats to screen for HAC. Curative treatment options include adrenalectomy or transsphenoidal hypophysectomy. Radiation or medical treatment may improve clinical signs. The response to mitotane therapy is poor. While trilostane is the medical treatment of choice based on retrospective studies, investigations into the pharmacokinetics of this drug in cats are lacking. Global importance: Feline HAC occurs worldwide and is not associated with any purebreed predisposition. Although uncommon, adrenal sex steroid-producing tumours have a higher prevalence in cats than in dogs. Evidence base: The information in this review is drawn from over 180 reported cases of feline HAC. Reports investigating clinical presentation, clinicopathological findings and treatment outcomes are observational, retrospective multiple case series (EBM grade III) or single case reports (EBM grade IV). While most endocrine testing studies for diagnosis are cohort controlled analytical studies (EBM grade III), prospective, randomised, placebo-controlled studies have been performed (EBM grade I).

Multiple Endocrine Neoplasia Type-I-like Syndrome in Two Cats

Multiple endocrine neoplasia (MEN) embodies a group of diseases in human patients and domestic animals that are characterized by hyperplasia or neoplasia, or both, of two or more endocrine tissues. The MEN-1 syndrome is associated with menin gene mutations that induce various combinations of parathyroid, pituitary, and pancreatic endocrine tumors in humans. Two male, Domestic Shorthair cats developed symmetric alopecia, insulin-resistant diabetes mellitus, and pituitary-dependent hyperadrenocorticism at 12 and 13 years of age. Examination of skin biopsy specimens revealed atrophic dermatosis associated with hyperadrenocorticism. In one cat, cutaneous lesions consistent with paraneoplastic alopecia associated with pancreatic adenocarcinoma also were evident. Multiple invasive pancreatic beta cell carcinomas, pituitary corticotroph adenomas, and thyroid C-cell and parathyroid chief cell hyperplasia were diagnosed on the basis of results of gross, histologic, and immunohistochemical findings in both cats. Pancreatic exocrine adenocarcinoma was diagnosed in both cats. one cat also had hepatocellular carcinoma. Exons 1-8 of the feline menin gene were sequenced and were found to bear 93% homology with the human gene sequence, and the corresponding amino acid sequences shared 98% homology. Purification of total RNA and amplification of cDNA from lesional tissues to document mutations in the feline menin gene sequence were unsuccessful. The combination of lesions observed was consistent with the diagnosis of MEN-1-like syndrome in both cats.

Clinical findings, diagnostic test results, and treatment outcome in cats with spontaneous hyperadrenocorticism: 30 cases

Background

Spontaneous hyperadrenocorticism (HAC) is rare in cats. Clinical findings, diagnostic test results, and response to various treatment options must be better characterized.

Objectives

To report the clinical presentation, clinicopathologic findings, diagnostic imaging results, and response to treatment of cats with HAC.

Animals

Cats with spontaneous HAC.

Methods

Retrospective descriptive case series.

Results

Thirty cats (15 neutered males, 15 spayed females; age, 4.0–17.6 years [median, 13.0 years]) were identified from 10 veterinary referral institutions. The most common reason for referral was unregulated diabetes mellitus; dermatologic abnormalities were the most frequent physical examination finding. Low‐dose dexamethasone suppression test results were consistent with HAC in 27 of 28 cats (96%), whereas ACTH stimulation testing was suggestive of HAC in only 9 of 16 cats (56%). Ultrasonographic appearance of the adrenal glands was consistent with the final clinical diagnosis of PDH or ADH in 28 of 30 cats (93%). Of the 17 cats available for follow‐up at least 1 month beyond initial diagnosis of HAC, improved quality of life was reported most commonly in cats with PDH treated with trilostane.

Conclusions and Clinical Importance

Dermatologic abnormalities or unregulated diabetes mellitus are the most likely reasons for initial referral of cats with HAC. The dexamethasone suppression test is recommended over ACTH stimulation for initial screening of cats with suspected HAC. Diagnostic imaging of the adrenal glands may allow rapid and accurate differentiation of PDH from ADH in cats with confirmed disease, but additional prospective studies are needed.

Concurrent somatotroph and plurihormonal pituitary adenomas in a cat

An 8-year-old, male neutered, domestic longhair cat was referred for investigation of insulin-resistant diabetes mellitus. Routine haematology, serum biochemistry, urinalysis (including culture), total T4 and urine creatinine:cortisol ratio were unremarkable, but markedly increased insulin-like growth factor-1 concentration was identified and a pituitary mass was subsequently documented. The cat was treated conservatively with the dopamine agonist L-deprenyl and was re-presented 16 months later for worsening polyuria, polydipsia, polyphagia, marked lumbar muscle atrophy, development of a pendulous abdomen and marked thinning of the abdominal skin. Hyperadrenocorticism was diagnosed based on abdominal ultrasonography, dexamethasone suppression testing and endogenous adrenocorticotropic hormone (ACTH). The cat was treated with trilostane (30 mg q24h PO) and showed some clinical improvement, but developed an opportunistic fungal infection and skin fragility syndrome 4.5 months after commencing treatment, and was euthanased. A double-pituitary adenoma comprising a discrete somatotroph adenoma and a separate plurihormonal adenoma (positive immunoreactivity for ACTH, melanocyte-stimulating hormone and follicle-stimulating hormone) was identified on post-mortem examination. These two pituitary adenomas were suspected to have arisen as independent neoplastic entities with the plurihormonal tumour either being clinically silent at the initial presentation or having developed over the subsequent 16 months.

Ultrasonographic appearance of adrenal glands in healthy and sick cats

The first part of the study aimed to describe prospectively the ultrasonographic features of the adrenal glands in 94 healthy cats and 51 chronically sick cats. It confirmed the feasibility of ultrasonography of adrenal glands in healthy and chronically sick cats, which were not statistically different. The typical hypoechoic appearance of the gland surrounded by hyperechoic fat made it recognisable. A sagittal plane of the gland, not in line with the aorta, may be necessary to obtain the largest adrenal measurements. The reference intervals of adrenal measurements were inferred from the values obtained in the healthy and chronically sick cats (mean ± 0.96 SD): adrenal length was 8.9-12.5 mm; cranial height was 3.0-4.8 mm; caudal height was 3.0-4.5 mm. The second part of the study consisted of a retrospective analysis of the ultrasonographic examination of the adrenal glands in cats with adrenal diseases (six had hyperaldosteronism and four had pituitary-dependent hyperadrenocorticism) and a descriptive comparison with the reference features obtained in the control groups from the prospective study. Cats with hyperaldosteronism presented with unilateral severely enlarged adrenal glands. However, a normal contralateral gland did not preclude a contralateral infiltration in benign or malignant adrenal neoplasms. The ultrasonographic appearance of the adrenal glands could not differentiate benign and malignant lesions. The ultrasonographic appearance of pituitary-dependent hyperadrenocorticism was mainly a symmetrical adrenal enlargement; however, a substantial number of cases were within the reference intervals of adrenal size.

Multiple endocrine diseases in cats: 15 cases (1997-2008)

The objective of this retrospective study was to characterize a population of cats from a tertiary care center diagnosed with multiple endocrine disorders, including the specific disorders and time intervals between diagnosis of each disorder. Medical records of 15 cats diagnosed with more than one endocrine disorder were reviewed. The majority of cats were domestic shorthairs, and the mean age at the time of diagnosis of the first disorder was 10.3 years. The most common combination of disorders was diabetes mellitus and hyperthyroidism. Two cats had concurrent diabetes mellitus and hyperadrenocorticism, one cat had concurrent central diabetes insipidus and diabetes mellitus. A mean of 25.7 months elapsed between diagnoses of the first and second endocrine disorder, but this was variable. This study suggests the occurrence of multiple endocrine disorders is uncommon in cats.

Hyperaldosteronism and hyperprogesteronism in a cat

CLINICAL FINDINGS AND INVESTIGATIONS: A 14-year-old female neutered domestic shorthair cat was referred for investigation of progressive hair loss, muscle wasting and hind limb weakness. Diabetes mellitus had been diagnosed 8 months earlier and was well controlled. Abnormalities on serum biochemistry included persistent mild azotaemia, hypochloridaemia, hypokalaemia, metabolic alkalosis and elevated creatine kinase. Physical examination revealed a pot-bellied appearance, with muscle wasting, marked thinning and fragility of the skin, bilaterally symmetrical alopecia, a gallop rhythm and systolic hypertension (173 mmHg). A large, lobulated left adrenal mass was identified using abdominal ultrasound. CONFIRMATION OF DIAGNOSIS: Primary hyperaldosteronism was diagnosed based on an elevated plasma aldosterone concentration and normal plasma renin activity. Hyperprogesteronism was confirmed by adrenocorticotrophic hormone stimulation test.

PRACTICAL RELEVANCE

This is only the second reported case of hyperaldosteronism and hyperprogesteronism in the cat. Clinicians should be alert to the possibility of concurrent hyperaldosteronism and hyperprogesteronism in cats with adrenal tumours showing clinical signs referable to both conditions. The putative mechanism is either increased secretion of aldosterone and progesterone from neoplastic cells of the zona glomerulosa and fasciculata/reticularis, respectively, or increased production of progesterone, as an intermediate in the synthesis of aldosterone, from neoplastic cells of the zona glomerulosa alone.

Pituitary Macroadenoma in a Cat with Diabetes Mellitus, Hypercortisolism and Neurological Signs

A 13-year-old neutered male European short-hair cat was presented because of blindness and behavioural abnormalities. On physical examination, abnormal behaviour, compulsive walking, circling, continuous vocalization and blindness were the main neurological signs. In addition, abdominal alopecia, thin and inelastic skin, weight loss despite polyphagia, polyuria and polydipsia were present. Laboratory investigation revealed diabetes mellitus and pituitary-dependent hypercortisolism. Diagnostic imaging showed bilaterally enlarged adrenals and a large pituitary mass. Histopathological and immunohistochemical examination confirmed the clinical diagnosis of an ACTH-producing pituitary macroadenoma.

Feline diabetes mellitus in the UK: the prevalence within an insured cat population and a questionnaire-based putative risk factor analysis

Prevalence and risk factors for the development of diabetes mellitus (DM) in cats in the United Kingdom have not previously been reported. The prevalence of DM was evaluated in a large insured population and was found to be 1 in 230 cats. In this insured cat population Burmese cats were 3.7 times more likely to develop DM than non-pedigree cats. A convenience-sampling questionnaire-based study was used in order to identify putative risk factors for the development of DM. The univariate risk factor analysis identified being male, neutered, inactive, weighing >or=5 kg and having a history of corticosteroid treatment as significant risk factors for the development of DM in these cats. In addition, male cats treated with megestrol acetate had a significantly increased risk of developing DM compared to females. In contrast, there was no difference in DM occurrence between male and female Burmese cats. A multivariate classification tree-based model on the questionnaire data looking for interactions between risk factors, identified gender as the most important overall risk factor for the development of DM with low physical activity being the next most important risk factor for female cats and breed the next most important for male cats.

Feline Adrenal Disorders

Although only recently discovered, feline adrenal disorders are becoming increasingly more recognized. Feline adrenal disorders include diseases such as hyperadrenocorticism (Cushing's syndrome) and hyperaldosteronism (Conn's syndrome). The clinical signs of feline hyperadrenocorticism, which include unregulated diabetes mellitus and severe skin atrophy, are unique to the cat. Other signs of feline hyperadrenocorticism, such as potbellied appearance, polydipsia, polyuria, and susceptibility to infections are also seen in dogs with hyperadrenocorticism. Conn's syndrome has only recently been described in the cat and is in fact more common in cats than in dogs. Characterized by severe hypokalemia, hypertension, and muscle weakness, Conn's syndrome may be misdiagnosed as renal failure. The clinician should become familiar with the clinical signs of adrenal disorders in cats and the common diagnostic tests used to diagnose these syndromes in cats as they differ from those in the dog. Treatment of feline adrenal disorders may be challenging; the clinician should become familiar with common drugs used to treat adrenal disorders in cats.

Iatrogenic Hyperadrenocorticism in 12 Cats

Iatrogenic hyperadrenocorticism is an extremely rare condition in cats. Twelve cats with a medical history of progressive skin lesions and long-term treatment with corticosteroids were retrospectively studied. Noncutaneous signs in the cats were variable and included anorexia, lethargy, polydipsia, polyuria, and atrophy of the thigh muscles. Laboratory abnormalities included leukocytosis, elevated alanine aminotransferase levels, and hyperglycemia. Transient diabetes mellitus was a secondary complication in four cats, and transient hypothyroidism was suspected in four cats. The mean time for regression of signs was 4.9 months after corticosteroid withdrawal.

Use of trilostane for the treatment of pituitary-dependent hyperadrenocorticism in a cat

Hyperadrenocorticism occurs much less frequently in cats than in dogs and, at present, is more difficult to manage successfully. This report documents the use of the steroid synthesis inhibitor trilostane for the treatment of hyperadrenocorticism in a domestic shorthaired cat with pituitary-dependent disease. Although trilostane was able to alleviate the severity of the clinical signs and was well tolerated, the cat subsequently died of renal failure secondary to a fungal infection of the urinary tract.

Diabetes mellitus and bilateral cataracts in a kitten

An 18-week-old male domestic long-hair kitten was presented with a history of polyuria and polydipsia for several weeks. The general condition was unremarkable, but the kitten was considerably smaller than expected for the age and showed cataracts in both eyes. Serum glucose concentrations were persistently elevated and based on clinical findings and an elevated serum fructosamine concentration, a diagnosis of diabetes mellitus was established. Diabetes mellitus is not commonly diagnosed in young kittens, nor are cataracts recognised as a frequent feature of this disease in cats. The cataracts progressed in spite of the insulin therapy and the kitten was euthanised 10 weeks after referral. Histopathological examination of the pancreas revealed few and small islets of Langerhans compared to the examination of pancreas from a healthy kitten of the same age. Histopathological changes in the eyes included cataracts affecting both cortex and nucleus.

Hypophysectomy as a treatment for canine and feline Cushing's disease

The microsurgical technique of transsphenoidal hypophysectomy performed with the dogs and cats positioned in sternal recumbency enables the treatment of Cushing's disease, independent of skull type, in a safe and effective manner. In dogs, the short-term survival rate after hypophysectomy is comparable to that after treatment with o,p'-DDD, whereas the recurrence rate in this period is lower. When the surgeon has gone through a learning curve, the results of the 1- to 3-year follow-up interval may be better than those after adrenocorticolysis with o,p'-DDD. CT enables assessment of localization and size of the pituitary before surgery. In general, dogs with Cushing's disease and normal-sized pituitaries or moderately enlarged pituitaries (up to 12 mm in diameter) are suitable candidates for transsphenoidal surgery. In dogs with larger pituitary tumors and tumor extension rostrally or caudally over the dorsum sellae, transsphenoidal debulking surgery may be only a palliative treatment. The main complications are postoperative hypernatremia, keratoconjunctivitis sicca, diabetes insipidus, and secondary hypothyroidism. In cats, special attention should be paid to closure of the soft palate. The neurosurgeon must be familiar with these complications so as to recognize them as early as possible and to treat them immediately and effectively. It is concluded that microsurgical transsphenoidal hypophysectomy in dogs and cats with Cushing's disease is an effective method of treatment.

Management of feline diabetes mellitus

Up to one quarter of diabetic cats can be well controlled with oral hypoglycemic drugs, although at least 75% require insulin therapy. Most available insulins provide good clinical control but only moderate glycemic control. Because mild to moderate hyperglycemia is well tolerated by cats receiving insulin but hypoglycemia can be life threatening, conservative insulin dosing is recommended. Clinical signs and water intake indicate whether a dose adjustment is required, but serial blood glucose measurements are usually needed to determine the direction of the adjustment. Starting doses of 0.3 to 0.5 IU/kg administered twice daily (rounded down to the nearest whole unit) are usually safe. Dose adjustments should not exceed 1 IU per cat every 2 to 4 weeks unless clinical hypoglycemia has occurred. Cats with clinical hypoglycemia need to be reassessed to see if they are in remission. If not, a 50% to 75% reduction in dose is advised. Approximately 30% of cats go into diabetic remission 1 to 4 months after an adequate treatment protocol is instituted.

Iatrogenic hyperadrenocorticism in a cat following a short therapeutic course of methylprednisolone acetate

Iatrogenic hyperadrenocorticism (or iatrogenic Cushing's syndrome) is an adrenal disorder that may result from long-term administration of glucocorticoids for therapeutic purposes, most often given to treat allergic or immune-mediated disorders. Prolonged treatment with synthetic glucocorticoids can suppress hypothalamic corticotrophin releasing hormone and plasma adrenocorticotrophic hormone (ACTH), thus causing a functional inactivity of the adrenal cortex. The result is a clinical syndrome of hyperadrenocorticism but with basal and ACTH-stimulated plasma cortisol concentrations that are consistent with spontaneous hypoadrenocorticism (Addison's disease). Whilst iatrogenic hyperadrenocorticism is relatively frequent in dogs, the diagnosis of iatrogenic hyperadrenocorticism in cats is very uncommon because this species has been found to be remarkably resistant to prolonged administration of glucocorticoids. To the author's knowledge, there are only two published clinical cases of feline iatrogenic Cushing's syndrome. This report describes a case of iatrogenic hyperadrenocorticism in a cat, and shows how normalisation of the adrenal function was achieved with supportive treatment and withdrawal of glucocorticoid administration.

Transsphenoidal hypophysectomy for treatment of pituitary-dependent hyperadrenocorticism in 7 cats

OBJECTIVE

Evaluation of microsurgical transsphenoidal hypophysectomy for the treatment of pituitary-dependent hyperadrenocorticism (PDH) in cats.

STUDY DESIGN

Prospective clinical study.

ANIMALS OR SAMPLE POPULATION

Seven cats with PDH.

METHODS

Urinary cortisol/creatinine ratios, pituitary-adrenocortical function tests, and computed tomography (CT) were performed on 7 cats that presented with a provisional diagnosis of hyperadrenocorticism. All cats underwent microsurgical transsphenoidal hypophysectomy with histologic examination of the excised specimen. Follow-up consisted of clinical evaluation, repeat adrenocortical function testing, and CT.

RESULTS

Four cats had concurrent diabetes mellitus. In all cats, the urinary cortisol/creatinine (C/C) ratios were elevated. The dexamethasone screening test showed that 2 cats did not meet the criterion for hyperadrenocorticism. The response of the cats' plasma concentrations of cortisol and adrenocorticotrophic hormone to a high dose of dexamethasone varied from very sensitive to completely dexamethasone resistant. Basal plasma alpha-melanocyte-stimulating hormone concentrations were elevated in 2 cats with a pars intermedia adenoma and in 3 cats with an adenoma that originated from the anterior lobe. Preoperative CT enabled accurate assessment of pituitary size (5 nonenlarged pituitaries with a height <4 mm and 2 enlarged pituitaries with a height >5 mm) and localization relative to intraoperative anatomic landmarks. Two cats died within 4 weeks after surgery of a nonrelated disease. In the remaining 5 cats, the hyperadrenocorticism went into both clinical and biochemical remission. Hyperadrenocorticism recurred in 1 cat after 19 months, but no other therapy was given and the cat died at home 28 months after surgery. CT evaluation of this cat had identified pituitary remnants 6 weeks after surgery. The main postoperative complications were oronasal fistula (1 cat), complete dehiscence of the soft palate (1 cat), and transient reduction of tear production (1 cat). One cat died at 6 months (undefined anemia), and another cat at 8 months (recurrent nose and middle ear infection secondary to soft palate dehiscence) after surgery. In the surviving 2 cats, the remission periods at the time of writing were 46 and 15 months. In the 2 cats with sufficient follow-up time, the concurrent diabetes mellitus disappeared, ie, insulin treatment could be discontinued at 4 weeks and 5 months after hypophysectomy. In all 7 cats, the histologic diagnosis was pituitary adenoma.

CONCLUSIONS

Microsurgical transsphenoidal hypophysectomy is an effective method of treatment for feline PDH in specialized veterinary institutions having access to advanced pituitary imaging techniques. Concurrent diabetes mellitus is usually reversible after hypophysectomy. Thorough presurgical screening for coexisting diseases is imperative.

CLINICAL RELEVANCE

PDH in cats can be effectively treated by hypophysectomy. The neurosurgeon performing hypophysectomy must master a learning curve and must be familiar with the most frequent complications of the operation to treat them immediately and effectively. Urinary C/C ratios are sensitive indicators for the assessment of remission and recurrence of hyperadrenocorticism.

Cortisol response to two different doses of intravenous synthetic ACTH (tetracosactrin) in overweight cats

Fifteen middle-aged to older, overweight cats attending a first-opinion clinic were investigated to rule out hyperadrenocorticism as a cause of their weight problem, using two different protocols for the adrenocorticotropic hormone (ACTH) stimulation test. The cats received intravenous synthetic ACTH (tetracosactrin) at an initial dose of 125 microg; a second test was performed between two and three weeks later, using a dose of 250 microg intravenously. The mean basal serum cortisol concentration was 203 nmol/litre (range 81 to 354 nmol/litre). The highest mean serum cortisol concentration occurred at 60 minutes following the 125 microg dose and at 120 minutes following the 250 microg dose. There was, however, no statistically significant difference between these peak cortisol concentrations attained using either dose of tetracosactrin. A significantly higher mean serum cortisol concentration was attained after the higher dose at the 180 minutes time point, indicating a more prolonged response when compared with the lower dose. The cats were followed up for one year after the initial investigations and none were found to develop hyperadrenocorticism during this time.

Hyperadrenocorticism treated with metyrapone followed by bilateral adrenalectomy in a cat

A 6-year-old spayed female cat was evaluated for uncontrolled diabetes mellitus and poor hair coat. Clinicopathologic abnormalities included high serum activity of liver enzymes, hyperglycemia, hypercholesterolemia, glucosuria, and an exaggerated response to ACTH stimulation. Abdominal ultrasonography revealed large adrenal glands. Hyperadrenocorticism was diagnosed. Treatment for a facial abscess was instituted along with administration of metyrapone for hyperadrenocorticism. After stabilization, bilateral adrenalectomy was performed. The cat recovered without complications and has remained clinically normal for 5 months with treatment of desoxycorticosterone pivalate and prednisone. Treatment with metyrapone appeared to stabilize the cat metabolically and clinically prior to surgery.

Use of abdominal ultrasonography in the diagnosis of primary hyperaldosteronism in a cat

A 13-year-old castrated male cat was examined because of a 2-week history of weakness, cervical ventroflexion, and dysphagia. Clinicopathologic abnormalities included hypokalemia and high serum creatine kinase activity. Abdominal ultrasonography revealed a 15-mm spherical mass in the area of the left adrenal gland. Plasma aldosterone concentration was high, and plasma renin activity was low. Findings were diagnostic of primary hyperaldosteronism. The cat responded well to intravenous and oral potassium supplementation while in the hospital. The owner declined surgery; therefore, repeated follow-up abdominal ultrasonography was recommended. The cat did well clinically with medical management alone until day 334, when it was lost to follow-up.

Ultrasonographic examination of the adrenal gland and evaluation of the hypophyseal-adrenal axis in 20 cats

The adrenal glands of 20 healthy, non-sedated cats were examined ultrasonographically; visualisation and assessment was possible in all cases. In comparison with the surrounding tissue, the adrenal glands were hypoechoic and two distinct zones could be differentiated in six of the cats. The length and width of the adrenal glands varied from 0.45 to 1.37 cm and 0.29 to 0.53 cm, respectively, and both dimensions could be reliably reproduced. The adrenal glands did not differ between male and female cats, and, in comparison to dogs, those of cats are more easily visualised ultrasonographically. The basal cortisol value ranged from 2.0 to 79 micrograms/litre. Values 30 and 60 minutes after administration of ACTH (0.125 mg/cat intramuscularly) varied from 36 to 126 micrograms/litre. The basal value of aldosterone ranged from 4 to 618 pg/ml. Values 30 and 60 minutes after administration of ACTH varied from 100 to 832 pg/ml. In all cats, suppression of the cortisol value below the level of detection (< 2.0 micrograms/litre) occurred four and eight hours after the administration of dexamethasone (0.1 mg/kg intravenously).