Influence ofl-Triiodothyronine on Steroid Hormone Metabolism: Studies in a Patient with Adrenal Hyperplasia (Cushing's Syndrome)

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Abstract
A low urinary excretion of the 5α-metabolite of cortisol, allo-THF, was previously reported by us to occur in patients with adrenal hyperplasia (Cushing's type). An attempt to increase 5α reduction by administering increasing amounts of l-triiodothyronine (T3)—0.2–0.8 mg/day—was made in a 17-yr-old boy with this syndrome. Progressive quantitative changes in individual C19 and C21 steroid metabolites excreted during T3 administration were compared with control periods during which no T3 was given, with the following results: 1) progressive increases in the following ratios of 5α/5β metabolites: androsterone/etiocholanolone, 0.3 to 1.3; allo-THF/THF, 0.1 to 0.7, and 11β-OH androsterone/11β-OH etiocholanolone, 0.2 to 0.8; 2) increased “total” cortisol metabolites; 3) increased absolute and relative amounts of THE; and 4) relatively constant excretion of THF, androsterone+etiocholanolone and percentage of allo-THF. These results suggest that thyroid hormone does increase steroid 5α-reductase activity as well as the rate of steroid-glucuronide formation in this type of patient and, presumably, in man in general. The ability of T3 to alter the biosynthesis of steroids in the adrenal is also indicated.

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