Changes in PTH Across the Spectrum of Renin-independent Aldosteronism

CONTEXT: Primary aldosteronism (PA) is the most common cause of endocrine hypertension. While elevated serum PTH levels have been associated with PA, the extent and nature of this relationship across the broader spectrum of renin-independent aldosteronism remain unclear. OBJECTIVE: This study aims to elucidate the relationship between PTH and aldosterone excess across the spectrum of renin-independent aldosteronism. DESIGN, SETTING, PARTICIPANTS: Adults screened for PA who also had a PTH measurement were retrospectively identified from the Monash Health Endocrine Hypertension Clinic (n = 462). Based on the aldosterone-to-renin ratio and results of the saline suppression test where applicable, patients were categorized into 3 groups: PA, low renin without PA, and non-PA. The association between PTH and PA status was evaluated. MAIN OUTCOME MEASURES: Serum PTH concentration. RESULTS: PTH levels were higher in patients with PA compared to low renin without PA and non-PA (median 5.7 vs 5.3 vs 5.1 pmol/L respectively, P < .05) despite comparable calcium and kidney function. Twenty-four-hour urinary calcium excretion increased progressively across the spectrum of renin suppression (4.1 vs 4.3 vs 4.9 mmol/day in non-PA, low renin without PA, and PA groups respectively, P < .05). Patients with PA were more likely to have elevated PTH with normal serum calcium concentration compared to those without PA (38% vs 28%, P = .010). CONCLUSION: Increasing PTH concentration and 24-hour urinary calcium excretion were observed across the spectrum of renin-independent aldosteronism. While PTH remained in the normal range for most patients, PA may be considered in patients with elevated PTH and normal serum calcium concentration.