Changes in serum vitamin A level during the human menstrual cycle.

THE purpose of the present investigation was to study the variations of serum vitamin A concentration in normal women in relation to the menstrual cycle. The wide variety of reports in the literature indicates that the equilibrium which exists between serum levels and liver stores of vitamin A is influenced by hormones (1–8). For example, Reichstein's compound L (3,β-acetoxy-17-α-hydroxy-allopregnan-20-one) appears to alter the equilibrium between blood and liver “A,” resulting in a decreased level of serum vitamin A and increased liver stores (1). Stimulation of the sympathetic nervous system with adrenaline increases the vitamin A content of the blood and mobilizes vitamin A from the liver (2). Combined injections of estradiol and testosterone have been reported to produce a threefold to fourfold increase in the concentration vitamin A in the blood serum of immature pullets (3). When growth hormone is given to vitamin A-deficient rats, a subacute deficiency of the vitamin is converted to an acute defici...