Aldosterone Secretion and Metabolism in Hyperthyroidism and Myxedema1

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Abstract
Aldosterone secretion and metabolism were studied in 12 patients with clear evidence of myxedema or hyperthyroidism. Studies were repeated after return of thyroid function to normal. The secretion rate of aldosterone, which was usually in the lower range of normal in myxedema, increased when thyroid was administered. The metabolic clearance of labeled aldosterone from plasma was low in hypothyroidism and increased when thyroid was given. Estimates of the miscible pool and mean concentration of aldosterone in plasma were within normal limits in myxedema and showed no significant or consistent change with treatment. In hyperthyroidism, more rapid disappearance of labeled aldosterone from plasma was reflected by high metabolic clearance rate and increased turnover in pools per day, which returned to normal when thyroid excess was corrected. In one hyperthyroid patient, a high normal secretion rate declined significantly after treatment. The other 6 patients secreted average normal quantities of aldosterone, with little or no decrease in secretion after return to the euthyroid state. Decreased pool size, a smaller apparent volume of distribution, and normal mean plasma aldosterone concentration were found in some of these hyperthyroid patients. The relative amounts of the major metabolites of aldosterone excreted in the urine were not affected by variation in thyroid function. These findings are compared with certain changes in cortisol secretion and metabolites observed simultaneously.