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A Separate Mechanism of Gonadotropin Recovery after Pregnancy Termination

Department of Obstetrics and Gynecology, University of Southern California School of Medicine Los Angeles, California 90033

Address requests for reprints to: Richard P. Marrs, M.D., Womens Hospital, 1240 North Mission Road, Los Angeles, California 90033.

To further elucidate the mechanism of return of pituitary secretory function after gestation, eight women were studied for up to 55 days after pregnancy termination. As long as serum estradiol (E₂) and progesterone (P) levels were elevated, serum FSH remained low. Four to 6 days after abortion, serum E₂ and P decreased to levels seen in the early follicular phase, and thereafter the initial increase in FSH occurred while serum β-LH remained undetectable. After the initiation of FSH secretion, the levels fluctuated within the normal follicular phase range, resulting in a steady increase of E₂ to a mean preovulatory peak of 257 ± 37 pg/ml at a mean time of 21 ± 1.3 days after pregnancy termination. This E₂ peak was followed by FSH and LH peaks and subsequent ovulation. In contrast to FSH, serum β-LH levels increased only after PRL concentrations diminished to 30 ng/ml or less. This initiation of β-LH secretion followed the advent of FSH secretion in six of eight patients. Therefore, a temporally separate mechanism of FSH and LH secretion after pregnancy termination is theorized. The recovery of FSH occurs soon after the E₂ and P levels decline while PRL levels are still elevated. However, the secretion of β-LH increases only after PRL reaches a normal or near-normal range at a time when E₂ levels have risen from the postabortion decline.

Received May 15, 1980.