Simultaneous Effects of Estradiol on TSH Secretion and Adrenocortical Function in Male and Female Rats

Sex differences in TSH secretion and adrenal function were revealed in adult male and female Sprague-Dawley rats after chronic administration (14 days) of estradiol benzoate (EB). The effect of the steroid on the pituitarythyroid and adrenocortical systems was dose dependent. Relatively little change in the various indices of adrenal function (gland weight, plasma and adrenal corticosteroids) was seen in the female rat with all dose levels of EB treatment (.1, 1, 10 and 50 μg daily). TSH content of the enlarged pituitary progressively declined, however. Plasma TSH titers also fell. This was accompanied by histological alterations indicative of reduced secretion in the thyroid. The response of the adrenal in estradiol-treated male rats was biphasic. Lower doses (10 and 50 μg) produced adrenal hypertrophy and sharp elevation in plasma and adrenal corticosteroid concentrations. With higher doses of EB (150 μg), all indices of adrenal activity remained normal. TSH content of plasma and adenohypophysis was not...