THE DISAPPEARANCE OF HCG AND RETURN OF PITUITARY FUNCTION AFTER ABORTION

Abstract

Plasma concentrations of hCG[human chorionic gonadotropin]/LH [lutropin] and FSH [follitropin] were monitored after a 1st trimester abortion in 18 healthy female volunteers 3 times/wk until the onset of 1st menstruation. Plasma hCG concentrations were measured with a specific RIA [radioimmunoassay] for the .beta.-subunit (.beta.-sub hCG) from the samples of 6 of these subjects. The elimination of hCG during the 1st 12 days was studied from plasma concentrations measured by RIA of LH. The experimental data were well explained by a mathematical model consisting of 3 exponentially decreasing components. The half-lives of the 2 more slowly decreasing components were 27 and 168 h. The estimate of the complete disappearance of hCG was 37.7 days, when the specific .beta.-sub-hCG assay was used. Recovery of pituitary function occurred within 4-9 days after abortion, as judged by increased plasma FSH concentrations. In 14 of 18 subjects a midcycle LH peak was observed which occurred between 16 and 29 days after abortion. Plasma estradiol concentrations increased 2-16 days after the rise in plasma FSH. Considerable amounts of hCG still circulated in the blood but the preovulatory estradiol peak never began before hCG/LH concentrations had decreased to below the range of the mid-cycle LH peak.