Age-Related Autonomous Aldosteronism
Background—Both aging and inappropriate secretion of aldosterone increase the risk for developing cardiovascular disease; however, the influence of aging on aldosterone secretion and physiology is not well understood.
Methods—The relationship between age and adrenal aldosterone synthase (CYP11B2) expression was evaluated in 127 normal adrenals from deceased kidney donors (age 9mo-68y). Following immunohistochemistry, CYP11B2 expressing area and areas of abnormal foci of CYP11B2 expressing cells, called aldosterone-producing cell clusters (APCCs), were analyzed. In a separate ancillary clinical study of 677 participants without primary aldosteronism, who were studied on both high and restricted sodium diets (age 18-71y), we used multivariable linear regression to assess the independent associations between age and renin-angiotensin-aldosterone system physiology.
Results—In adrenal tissue, the total CYP11B2 expressing area was negatively correlated with age (r=−0.431, P <0.0001), whereas the total APCC area was positively correlated with age (r=0.390, P<0.0001). The integrated ratio of APCC to CYP11B2 expressing area was most strongly and positively correlated with age (r=0.587, P < 0.0001). When participants in the clinical study were maintained on a high sodium balance, renin activity progressively declined with older age, whereas serum and urinary aldosterone did not significantly decline. Correspondingly, the aldosterone-to-renin ratio (ARR) was positively and independently associated with older age (adjusted β=+5.54 ng/dL per ng/mL/h per 10 years, P<0.001). In contrast, when participants were assessed under sodium restricted conditions, physiologic stimulation of aldosterone was blunted with older age (β=−4.6 ng/dL per 10 years, P<0.0001).
Conclusions—Aging is associated with a pattern of decreased normal zona glomerulosa CYP11B2 expression and increased APCC expression. This histopathologic finding parallels an age-related autonomous aldosteronism and abnormal aldosterone physiology that provides one potential explanation for age-related cardiovascular risk.
- Received March 4, 2017.
- Revision received April 25, 2017.
- Accepted May 15, 2017.