High Correlation of Serum Inhibin A and B with Gonadotropin Levels in Oligo-amenorrheic Women with Polycystic Ovary Syndrome

Roh, J S; Ji, I W; Son, B R; Kim, H S

Abstract

OBJECTIVES
Normal and abnormal follicular growth and steroidogenesis depend on gonadotropins as well as intraovarian peptides. Inhibin also affect follicular development and steroidogenesis and may play a role in dominant follicle selection and follicular atresia. Therefore, we studied the differences of serum inhibin A, inhibin B and gonadotropin levels according to the regularity of menstrual cycle in the women with polycystic ovary syndrome[PCOS]. Materials and
METHODS
Women who showed typical appearance of polycystic ovaries by transvaginal ultrasonography and had basal serum levels of luteinizing hormone > 5.8 IU/L or LH/FSH ratio > 1.2 were selected. Patients with abnormal prolactin level or thyroid function were excluded. Among PCOS, fifteen women had had normal regular menstrual cycles[25~35 days] for at least 6 months before the study, and the others had been oligo-amenorrheic. Blood samples were obtained on the cycle day 3~5 after normal menstrual or progesterone withdrawal bleeding. Serum levels of inhibin A, inhibin B, luteinizing hormone[LH], follicle stimulating hormone[FSH], estradiol[E2], testosterone[T] and dehydroepiandrosterone-sulfate[DHEA-S] were compared and analysed between the two groups. Statistical analysis was performed using Student`s t-test and the Spearman correlation coefficient.
RESULTS
Serum LH, T levels and LH/FSH ratio were significantly greater in the group with oligo-amenorrheic, cycle than those in regular cycle. Basal levels of inhibin A and B were not different between the two groups. A significant negative correlation between inhibin A and FSH level was seen in the group with oligo-amenorrhic cycle[P<0.005], but not in the group with regular cycle. Also significant positive correlation was noted between inhibin B level and LH/FSH ratio in the group with oligo-amenorrheic cycle[P<0.001], but not in the group with regular cycle.
CONCLUSION
In oligo-amenorrheic PCOS, higher LH[or LH/FSH] may cause hypertrophy of thecal cells and stimulate androgen and inhibin secretion. In addition, higher androgen can be converted into estrogen by extraovarian tissues. Thus, inhibin A, B and steroids [T, estradiol] may exaggerate disparity in basal LH and FSH levels, and be directly associated with ovulatory disturbance in PCOS, otherwise, in which the endocrine or paracrine influence of inhibin A, B might be enhanced.