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.
OBJECTIVE
Interest has focused recently on the influences of the polypeptide factors inhibin and activin on the selective regulation of the pituitary secretion of gonadotropins.


METHODS
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 microg 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 significant 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 significant change between baseline and the 60 min value, whereas inhibin B was characterized by a minor, but not significant, increase in the median from 168 to 179 pg/ml (P = 0.408). A significant inverse correlation (P = 0.014) with a mean coefficient 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.


CONCLUSIONS
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.
Casper
F W
FW
Department of Experimental Endocrinology, Johannes Gutenberg University Mainz, D-55101 Mainz, Germany. casper@mail.uni-mainz.de
Seufert
R J
RJ
Pollow
K
K
D028341:Activins; D000293:Adolescent; D000328:Adult; D000568:Amenorrhea / Q000097:blood / Q000209:etiology; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone; D006801:Humans; D007006:Hypogonadism / Q000209:etiology; D007027:Hypothalamic Diseases / Q000150:complications; D007265:Inhibins / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D010049:Ovarian Diseases / Q000097:blood*
D028341:Activins; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone