Inverse correlation between baseline inhibin B and FSH after stimulation with GnRH: a study of serum levels of inhibin A and B, pro alpha-C and activin A in women with ovulatory disturbances before and after stimulation with GnRH

Abstract

Objective: Interest has focused recently on the in¯uences of the polypeptide factors inhibin and activin on the selective regulation of the pituitary secretion of gonadotropins. Design: Measurement of the concentrations of inhibin-related proteins in relation to the changes in pituitary gonadotropin (FSH, LH) parameters, after GnRH stimulation with a bolus injection of 100 mg gonadorelin, in 19 women with ovulatory disturbances. Methods: Serum levels of inhibin A and B, activin A, and pro alpha-C were measured using sensitive ELISA kits. Results: Within 60 min after GnRH stimulation, FSH values doubled from 5 to 10 mU/ml (P < 0.001). LH increased 12-fold from 2 to 24 mU/ml (P < 0.001). Activin A showed a signi®cant decrease from 0.47 to 0.36 ng/ml (P < 0.001), whereas pro alpha-C increased from 127 to 156 pg/ml (P 0.039). The median inhibin A concentration did not show a signi®cant change between baseline and the 60 min value, whereas inhibin B was characterized by a minor, but not signi®cant, increase in the median from 168 to 179 pg/ml (P 0.408). A signi®cant inverse correlation (P 0.014) with a mean coef®cient of correlation of 0.5516 was found, demonstrating a strong relationship between high inhibin B baseline levels and a small increase of FSH after 60 min. Conclusion: Our results show an interesting correlation between the baseline inhibin B and the change in FSH before and after GnRH stimulation. A high baseline inhibin B implies only a minor increase of FSH after 60 min.

The ovarian markers of the FSH insufficiency in functional hypothalamic amenorrhoea

“…The basal level was considered as normal in the study by Petraglia et al (1998), but their norms were significantly lower than those published later in a larger series (Pigny et al, 2000). In the study by Casper et al (2000), the increase of inhibin B was not significant after GnRH stimulation while FSH levels doubled and LH levels increased 12-fold. However, the studied population did not exclusively contain patients with FHA.…”

“…In normal women in EFP, inhibin B is secreted by granulosa cells in response to the inter-cycle FSH rise, just before the induction of estradiol (E 2 ) secretion (Hayes et al, 1998). Only two studies have previously addressed the inhibin B status in FHA (Petraglia et al, 1998;Casper et al, 2000). The basal level was considered as normal in the study by Petraglia et al (1998), but their norms were significantly lower than those published later in a larger series (Pigny et al, 2000).…”