Secretion Rate of Aldosterone in Normal Pregnancy.

There is a progressive rise in excretion of the metabolites of the estrogens (1) and of progesterone 1 (2) during pregnancy in humans. In late pregnancy, these hormones are largely placental in origin (3-6). The physiological role of the adrenal gland in pregnancy is still not well understood. The high levels of blood hydrocortisone found in pregnancy were initially explained as a reflection of an increased secretion of adrenal cortical hormones (7). More recently, it has been shown that the high blood levels of hydrocortisone in pregnancy could be accounted for by the increased binding of this hormone to blood proteins (8). It has been reported that aldosterone is secreted in increased amounts during pregnancy (9, 10). From available evidence, it has been concluded that in humans aldosterone is not a secretory product of the placenta (11-14), but that it is formed in the adrenal gland. In earlier studies (15-17), bioassay of the crude urinary extract revealed little or no increase in the salt-retaining factor in pregnancy as compared with the normal nonpregnant state. Barnes and Quilligan (18) reported the same findings with a bioassay of urinary extracts purified by three paper chromatographic systems. In 1956, Venning and Dyrenfurth (19) bioassayed extracts