Hypophyseal Mediation of Estrogen-Induced Hypocholesterolemia

Abstract

Although under certain conditions the administration of estrogenic substances has been reported to result in an increase in serum cholesterol in the rat (1,2), relatively large doses of estrogen will produce a marked depression in cholesterol concentration in the serum and adrenal glands in this species (3,4). Cholesterol has been shown to be an obligatory precursor in the biosynthetic pathway to adrenal steroid hormones (5). It is believed that the free cholesterol of the adrenal may be derived from the plasma cholesterol (6), or exchanges with plasma cholesterol after synthesis in situ. In attempting to explain the mode of action of estrogens in cholesterol metabolism, Levin (3) proposed that the adrenal gland, subjected to continual and excessive stimulation by endogenous pituitary corticotropin in estrogen-treated rats, converted cholesterol at such a rate that its own stores as well as those of the serum became depleted. However, Barakat (2) reported an increase in the serum cholesterol of hypophysectomized rats on treatment with corticotropin, although this hormone had no effect on serum cholesterol in intact rats.