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Regulation of Human Gonadotropins: II. Disappearance of Human Chorionic Gonadotropin Following Delivery¹

Departments of Pathology and Obstetrics and Gynecology, The University of Michigan Ann Arbor, Michigan 48104

The levels of HCG in the serum and urine of post-partum women have been measured by RIA over a period of several days. The rate of disappearance of HCG from the serum decreased with time, resulting in an apparent progressive increase in the half-life of HCG during the first 3 days. The resulting composite disappearance curve appeared to be the result of 2 linear components, the first corresponding to a half-life of 8.9 hr and the second to a half-life of 37.2 hr. Similar half-life values were found for HCG present in newborn infants (9.1–16.8 hr) and for HCG injected into one nonpregnant subject (32 hr).

This study was supported by a research grant from the National Cancer Institute (NIH-CA-06115) and The National Institute of Child Health and Human Development (NIH-HD-02193).

¹ The first paper in this series was published as "Human luteinizing hormone in serum during the menstrual cycle: Determination by radioimmunoassay" (J Clin Endocr 26: 1375, 1966).

² Career Development Awardee of the National Institute of Child Health and Human Development.

³ Josiah Macy, Jr., Foundation Faculty Fellow.

Received February 26, 1968.

Accepted August 7, 1968.

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