Experimental Hyperthyroidism and Adrenocortical Function in the Rat

Chronic administration of triiodothyronine (T3) in high daily doses (40, 25 μg; 3–36 days) to male and female rats induced hyperactivity of the adrenal cortex, as indicated by marked increases in corticoid concentrations of plasma and adrenal and by hypertrophy of the gland. An inverse relationship was found between ascorbic acid and corticosterone concentration in adrenals of severely hyperthyroid animals. Adrenal ascorbic acid concentration was consistently reduced (14–24%) with higher doses of T3, while corticosterone levels in gland and plasma increased 2- to 4-fold and 40–80%, respectively. Ascorbic acid content of enlarged adrenals in the male increased significantly, however. It is concluded that in the hyperthyroid animal increased adrenocortical secretion occurs which can be maintained for at least several weeks. Cortical hormone elaboration by the adrenal in experimental hyperthyroidism bears no quantitative relationship to its ascorbic acid content. (Endocrinology74: 509, 1964)