Serum Levels and Expressions of Inhibin A and Inhibin B in the Ovaries of Perimenopausal Women

Kim, Jang Heub; Kim, Mee Ran; Lee, Yoon Jin; Hwang, Seong Jin; Jo, Hyun Hee; Ryu, Ki Sung; Lew, Young Ok; Han, Ku Taek; Rha, Jong Gu; Kim, Jin Hong

Abstract

OBJECTIVE
To understand the physiologic effects and secretion pattern of inhibin A and inhibin B during menstrual cycle and menopausal transition, inhibin A and inhibin B levels were measured. And to detect any changes in expression of inhibins in human ovary with age, we examined immunohistochemical staining of alpha, beta A, and beta B subunits of inhibin in ovarian tissues. This study was also designed to investigate whether or not inhibin is an early marker for menopausal transition.
METHODS
Inhibin A and inhibin B levels were measured in 320 samples from normal reproductive women, in 60 from perimenopausal women, and in 20 from menopausal women by ELISA. And we examined the immunohistochemical staining of alpha, beta A, and beta B subunits of inhibin in ovarian tissues of 35 normal reproductive, 20 perimenopausal, and 5 menopausal women, respectively.
RESULTS
In the normal reproductive women, inhibin A begins to increase in the late proliferative phase (16.53 +/- 1.57 pg/ml), reaches the peak in the mid-secretory phase (45.85 +/- 2.08 pg/ml), and subsequently decreases. Inhibin B begins to increase in the early proliferative phase (65.40 +/- 4.08 pg/ml), reaches the peak in the ovulatory phase (110.74 +/- 9.83 pg/ml), and thereafter declines rapidly. In the perimenopausal women, mean inhibin A serum concentration was 6.68 +/- 0.53 pg/ml during proliferative phase and 21.78 +/- 3.61 pg/ml during secretory phase, which were significantly lower than that of the same phase in the normal reproductive women (P<0.01). Mean inhibin B serum concentration was 52.16 +/- 7.46 pg/ml during proliferative phase and 22.41 +/- 6.73 pg/ml during secretory phase, which were significantly lower than that of the same phase in the normal reproductive women (P<0.01, P=0.025). In the menopausal women, both inhibin A and inhibin B were not detected. In the normal reproductive women, we observed strong immunostaining for alpha subunit in granulosa cells, theca cells, and corpus luteum. Immunostaining for beta A subunit was observed in corpus luteum, but not in growing follicles. Immunostaining for beta B subunit was observed in primary follicle, granulosa and theca cells of growing follicle, and mature follicle, but less strong than immunostaining for alpha subunit. No staining for beta B subunit was observed in the corpus luteum. In the perimenopausal women, immunostaining for inhibin subunits were observed in the same pattern as that of the normal reproductive women, but weaker. Stronger immunostaining was observed in theca cells than in granulosa cells. In the menopausal women, none of the immunostaining of inhibin subunits were observed.
CONCLUSION
It is concluded that inhibin A is associated with the luteal function and inhibin B, the follicular function. The secretion of inhibins decreased rapidly in the perimenopausal transition period and were not detected in the menopausal period. Inhibin A and inhibin B are associated with the follicular maturation and development. It suggests that the inhibin A and inhibin B are good candidates as markers for perimenopausal transition.