Plasma prorenin response to human chorionic gonadotropin in ovarian-hyperstimulated women: correlation with the number of ovarian follicles and steroid hormone concentrations

Plasma prorenin and active renin were measured
before and after human chorionic gonadotropin (hCG)
administration in two groups of patients undergoing ovarian
stimulation for 4-6 days with follicle-stimulating hormone
alone or in combination with luteinizing hormone, forin vitrofertilization. Baseline total plasma renin (prorenin plus active
renin;n= 12) averaged 25 ± 8 ng/ml per hr (mean ± SD).
Total renin did not change during ovarian stimulation but it
increased to 46 ± 16 ng/ml per hr (P< 0.05) 1 or 2 days later,
just before hCG administration. Thirty-six hours after hCG
administration, just before laparoscopy and egg retrieval, total
renin was 123 ± 97 ng/ml per hr; a peak of 182 ± 143 ng/ml
per hr occurred 2-6 days later-i.e., during the luteal phase of
the menstrual cycle. In eight of the patients who did not
conceive, total renin returned to baseline 14 days after hCG
administration. In four who conceived, a nadir was reached (57 ± 13 ng/ml per hr) 8-12 days after hCG administration and
then total renin increased again as the plasma βhCG measurement
began to rise. By day 16 it averaged 225 ± 157 ng/ml per
hr. In a second group of five patients active renin and prorenin
were measured separately. Active renin comprised <20% of
the total renin at all times. It was unchanged until day 4 after
hCG administration and then increased significantly only when
plasma progesterone was high. Thus, the initial response to
hCG was entirely due to an increase in prorenin. A highly
significant correlation was observed between the number of
follicles and the total renin increases on the day of aspiration
(r= 0.93,P< 0.001) and at the peak (r= 0.89,P< 0.001).
After hCG administration, a temporal relationship was observed
between the rise in total renin and plasma estradiol and
progesterone levels. These results demonstrate that plasma
prorenin increases markedly after administration of hCG and
that the rise is directly related to the number of ovarian follicles
and to plasma estrogen and progesterone levels. The findings
suggest that prorenin is produced by the mature ovarian follicle
and by the corpus luteum in response to gonadotropin stimulation.