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.