Is inhibin B a pharmacodynamic parameter for FSH in normal men?
OBJECTIVE
This study aims to investigate the pharmacodynamic effect of FSH on inhibin B serum levels in normal men in order to elucidate the physiological regulation of inhibin B secretion in more detail.


METHODS
Injections of 3000 IU recombinant, human FSH (rhFSH) were followed by single-blinded injections of placebo, 1000 and 2000 IU rhFSH spaced by at least 28 days between injections.


RESULTS
After injection of 3000 IU rhFSH, inhibin B values were significantly elevated above baseline for 24, 96 and 120 h (maximal increase after 96 h, mean +/- s.e.m. 303+/-18 pg/ml). Injection of 2000 IU rhFSH led to a significant increase in inhibin B (maximum mean +/- s.e.m. 318+/-20 pg/ml) from 24 to 120 h. Injection of 1000 IU rhFSH led to a significant increase in inhibin B after 96 h (maximum mean +/- s.e.m. 300+/-16 pg/ml). The inhibin B areas under the curve after injection of 2000 and 3000 IU rhFSH were significantly higher than those following the placebo and 1000 IU rhFSH. In the 12 fertile men investigated, at baseline a strong diurnal rhythm of inhibin B parallel to that of testosterone was observed.


CONCLUSIONS
Serum inhibin B can be considered only a partial pharmacodynamic parameter of FSH in vivo, since the integrity of the spermatogenic process appears to be a second fundamental component in the regulation of its secretion from the testis.
Kamischke
A
A
Institute of Reproductive Medicine of the University, Domagkstrasse 11, D-48129 Munster, Germany.
Simoni
M
M
Schrameyer
K
K
Lerchl
A
A
Nieschlag
E
E
D000328:Adult; D019540:Area Under Curve; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008297:Male; D029584:Prostatic Secretory Proteins; D011994:Recombinant Proteins / Q000494:pharmacology; D012016:Reference Values; D012611:Scrotum / Q000000981:diagnostic imaging; D012661:Semen / Q000737:chemistry; D013737:Testis / Q000000981:diagnostic imaging; D014463:Ultrasonography
D029584:Prostatic Secretory Proteins; D011994:Recombinant Proteins; C043076:beta-microseminoprotein; D007265:Inhibins; D005640:Follicle Stimulating Hormone