Evaluation of the Oral Fludrocortisone Suppression Test for Diagnosing Primary Hyperaldosteronism in Cats

Infraspinatus muscle necrosis in a cat with primary hyperaldosteronism

Case summary

Persistent and progressive weakness secondary to hypokalaemia, that is, hypokalaemic polymyopathy, is one of the most common clinical signs of primary hyperaldosteronism (PHA). Herein, we report a case of PHA with infraspinatus muscle necrosis. A 5-year-old castrated male domestic shorthair cat presented with a history of polyuria and polydipsia, decreased activity, staggering gait, difficulty in jumping and inward rotation of both forelimbs. Blood examination revealed hypokalaemia, increased serum creatinine kinase activity and high serum aldosterone concentration. Abdominal ultrasonography and CT revealed an enlarged right adrenal gland. Post-contrast thoracic CT showed peripheral contrast enhancement and a non-enhanced centre in the bilateral infraspinatus muscles. From the day of initial presentation, the cat was started on oral potassium replacement therapy. On day 17, the right adrenal gland was surgically resected and the left infraspinatus muscle was biopsied. Histopathological examination confirmed the presence of an adrenocortical adenoma in the right adrenal gland and necrosis of the muscle fibres in the left infraspinatus muscle. On day 29, all clinical signs had disappeared, and the serum potassium concentration, creatinine kinase activity and aldosterone concentration had normalised. On day 57, atrophy of the bilateral infraspinatus muscles was noted, but there was no evidence of any posture or gait abnormalities.

Relevance and novel information

To the authors' knowledge, this is the first report of possible infraspinatus muscle necrosis in a cat with PHA. It is also possible that the infrinatus muscle necrosis with hypokalaemic polymyopathy secondary to PHA was caused by compartment syndrome in the cat described here.

Prospective evaluation of a telmisartan suppression test as a diagnostic tool for primary hyperaldosteronism in cats

BACKGROUND

In a previous study, telmisartan suppressed aldosterone secretion in healthy cats but not in cats with primary hyperaldosteronism (PHA).

HYPOTHESES

Telmisartan suppresses aldosterone secretion in middle-aged healthy cat and cats with diseases that may result in secondary hyperaldosteronism, but not in those with PHA.

ANIMALS

Thirty-eight cats: 5 with PHA; 16 with chronic kidney disease (CKD), subclassified as hypertensive (CKD-H) or non-hypertensive (CKD-NH); 9 with hyperthyroidism (HTH); 2 with idiopathic systemic arterial hypertension (ISH); and 6 healthy middle-aged cats.

METHODS

Prospective, cross-sectional study. Serum aldosterone concentration, potassium concentration, and systolic blood pressure were measured before and 1 and 1.5 hours after PO administration of 2 mg/kg of telmisartan. The aldosterone variation rate (AVR) was calculated for each cat.

RESULTS

No significant difference in the minimum AVR was observed among groups (median [quartile 1 (Q1); quartile 3 (Q3)]: 25 [0; 30]; 5 [-27; -75]; 10 [-6; -95]; 53 [19; 86]; 29 [5; 78]) for PHA, CKD, HTH, ISH, and healthy cats, respectively (P = .05). Basal serum aldosterone concentration (pmol/L) was significantly higher in PHA cats (median [Q1; Q3]: 2914 [2789; 4600]) than in CKD-H cats (median [Q1; Q3]: 239 [189; 577], corrected P value = .003) and CKD-NH cats (median [Q1; Q3]: 353 [136; 1371], corrected P value = .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

The oral telmisartan suppression test using a single dose of 2 mg/kg telmisartan did not discriminate cats with PHA from healthy middle-aged cats or cats with diseases that may result in secondary hyperaldosteronism.

Evaluation of oral telmisartan administration as a suppression test for diagnosis of primary hyperaldosteronism in cats

BACKGROUND

Development of a telmisartan-based suppression test may facilitate the diagnosis of primary hyperaldosteronism (PHA) in cats, which remains difficult today.

OBJECTIVES

To develop a telmisartan suppression test (TST) that is safe, and able to suppress aldosterone secretion in healthy cats but not in cats with PHA.

ANIMALS

Ten healthy cats and 6 cats with PHA.

METHODS

Prospective study using a placebo-controlled crossover design to investigate a TST in healthy cats, and evaluation of TST in cats with PHA. Plasma aldosterone concentration, potassium concentration, and systolic blood pressure (SBP) were measured before (T0), and 1 hour (T1) and 1.5 hours after (T1.5) PO administration of 1 mg/kg of telmisartan, 2 mg/kg of telmisartan or placebo.

RESULTS

Median age in healthy cats was 3 years old (range, 1-7). In healthy cats, a telmisartan dose of 2 mg/kg significantly decreased aldosterone concentration at T1 and T1.5 compared with T0. Placebo had no significant effect on aldosterone concentration. In cats diagnosed with PHA, a 2-mg/kg dose of telmisartan did not induce any significant change in aldosterone concentration at T1 or T1.5 compared with T0. No adverse effects of telmisartan (e.g., hyperkalemia, systemic hypotension) were observed in any cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

The oral TST shows promise as a diagnostic test for the diagnosis of PHA in cats.

Retrospective study of aldosterone and progesterone secreting adrenal tumors in 10 cats

Background

Primary hyperaldosteronism caused by adrenal neoplasia has been well described in cats. Multiple corticosteroid abnormalities occur in a subset of affected cats, but characterizations of this syndrome are limited to several case reports.

Objectives

To describe a series of cats with adrenal tumors secreting aldosterone and additional corticosteroids.

Animals

Ten cats with multiple corticosteroid secreting adrenocortical tumors.

Methods

Retrospective case series. Medical records of cats with adrenal tumors secreting both aldosterone and progesterone were identified. Data concerning historical findings, clinicopathologic features, treatments, and outcomes were retrieved from medical records.

Results

All 10 cats had diabetes mellitus in addition to biochemical features of hyperaldosteronism such as hypokalemia. High corticosterone concentrations were observed in all 3 cats in which this corticosteroid was measured. Ultrasound examinations revealed unilateral adrenal tumors in all 10 cases, and the contralateral adrenal gland was either atrophied or not identified in 5 cats. Three of 4 cats developed hypoadrenocorticism after surgical adrenalectomy. Three cats achieved diabetic remission after adrenalectomy. Two cats treated with adrenalectomy survived >1 year, 1 cat survived 6.5 months, and 1 cat was alive 5.5 months after diagnosis. Survival >1 year occurred in 2 of 4 cats treated with medical management alone. Two cats were not treated.

Conclusions and Clinical Importance

The presence of multiple corticosteroid abnormalities should be considered in cats with aldosterone secreting adrenal tumors, especially those with concurrent diabetes mellitus. Both surgical and medical management can result in long‐term survival, although diabetic remission was documented only in cats undergoing adrenalectomy.

Multiple corticosteroid abnormalities in cats with hyperaldosteronism

Background

The frequency with which multiple corticosteroid abnormalities occur in cats with aldosterone secreting adrenocortical tumors is unknown.

Objectives

To evaluate adrenal‐derived corticosteroids in cats in which blood samples were submitted for measure of aldosterone.

Animals

Two hundred ninety‐seven cats.

Methods

Retrospective study. Analysis of a convenience sample of previously submitted serum or plasma. Progesterone, corticosterone, and cortisol were measured in feline serum or plasma samples submitted to an endocrinology laboratory for aldosterone measurements. Demographics and clinical history were retrieved from submittal forms when provided. Statistical testing was performed to investigate associations among the adrenal corticosteroids.

Results

Progesterone and corticosterone concentrations were strongly correlated (ρ = 0.74; P < .001). Progesterone (median, 5 nmol/L; interquartile range, 3‐10 nmol/L) and corticosterone (113 nmol/L, 38‐250 nmol/L) in cats with markedly increased aldosterone concentrations (≥3000 pmol/L) were higher than progesterone (1 nmol/L, 1‐2 nmol/L) and corticosterone (12 nmol/L, 3‐25 nmol/L) in cats with normal aldosterone concentrations (P < .001 for both comparisons). Progesterone concentrations ≥10 nmol/L (normal, ≤2 nmol//L) occurred in 24 of 76 (32%) cats with aldosterone concentrations ≥3000 pmol/L. Cortisol was lower in cats with aldosterone concentrations ≥3000 pmol/L as compared to those with aldosterone concentrations <500 pmol/L (59 nmol/L, 27‐103 nmol/L vs 103 nmol/L, 49‐182 nmol/L; P = .002).

Conclusions and Clinical Importance

Multiple corticosteroid abnormalities occur in a subset of cats with hyperaldosteronism. The magnitude of increases in progesterone and corticosterone in some cats with hyperaldosteronism is likely to be clinically relevant.

Primary Hyperaldosteronism in Cats: An Underdiagnosed Disorder

Primary hyperaldosteronism, also known as Conn's syndrome, is the most common adrenocortical disease in cats. As in humans, this disease is underdiagnosed in cats. Cats presenting with systemic arterial hypertension, hypokalemia, or both quite often are only treated symptomatically without further investigations. This practice may potentially exclude a significant number of cats from receiving appropriate treatment. It is therefore important for general practitioners to be aware of the disease. This article describes the (patho)physiology, clinical presentation, diagnostic approach, and treatment options of for feline primary hyperaldosteronism.

Serum aldosterone and cortisol concentrations before and after suppression with fludrocortisone in cats

Primary hyperaldosteronism is an increasingly recognized syndrome in cats, and diagnosis can be difficult. A potential diagnostic method has been reported, utilizing oral fludrocortisone administered twice daily for 4 days followed by collection of urine. In the current study, we sought to determine if blood sampling and a shorter dosing period would provide a possible means to test for primary hyperaldosteronism. Also, cortisol concentrations were measured to assess the potential of fludrocortisone to act as a glucocorticoid in cats. In phase I, 8 healthy laboratory cats were studied in a placebo-controlled, crossover design. Serum aldosterone and cortisol concentrations were measured before and on the second, third, and fourth day of treatment and compared within groups. In phase II, based on the results obtained in phase I, 8 healthy client-owned cats were administered 3 doses of fludrocortisone or placebo. Serum aldosterone and cortisol concentrations were compared before and after treatment within groups. In both phases, serum aldosterone and cortisol concentrations were significantly suppressed in fludrocortisone-treated cats. Thus, it was determined that oral administration of fludrocortisone causes suppression of serum aldosterone in healthy adult cats after only 3 doses. Further research is needed to determine the effects of oral fludrocortisone in cats with primary hyperaldosteronism and cats with other disorders causing hypertension and/or hypokalemia to determine if this protocol can be used as a tool for the definitive diagnosis of primary hyperaldosteronism.