Specific regulatory actions of dihydrotestosterone and estradiol on the dynamics of FSH secretion and clearance in humans.
The authors investigated immunoactive and bioactive follicle-stimulating hormone (FSH) secretion and clearance in six healthy young men during steady-state infusions of vehicle (basal, B, 28 hours), dihydrotestosterone (DHT, 4.5 days), or estradiol (4.5 days) accompanied by blood sampling at 10-minute intervals for 28 hours. Serum FSH concentrations were assayed by a two-site immunoradiometric assay (IRMA) and two separate in vitro bioassays (rat granulosa and Sertoli cell systems). FSH measurements included: 24-hour mean serum concentrations (IRMA and bioassay), multiple-parameter deconvolution of 24-hour pulsatile FSH time series and FSH release in response to exogenous gonadotropin-releasing hormone (GnRH) boluses (IRMA) to assess secretion and clearance, and circadian serum FSH concentration rhythms by cosinor analysis (IRMA). We found: 1) a significant decrease in 24-hour mean IRMA FSH concentrations during DHT infusion while both in vitro estimates of FSH bioactivity were unchanged; 2) significant decreases in the mass of IRMA FSH secreted per 24 hours during DHT infusion; 3) significant decreases in the IRMA FSH half-life during estradiol infusion without any change in FSH interpulse interval; 4) no steroidal effects on FSH secretory responses to exogenous GnRH; and 5) abolition of basal circadian FSH rhythms during sex-steroid infusions. Based on these findings, we conclude that steady-state sex-steroid hormone infusions selectively alter IRMA FSH secretion and clearance without affecting IRMA FSH pulse frequency or mean concentrations of bioactive FSH.
Urban
R J
RJ
Department of Internal Medicine, University of Virginia, Charlottesville.
Dahl
K D
KD
Padmanabhan
V
V
Beitins
I Z
IZ
Veldhuis
J D
JD
D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm; D002985:Clinical Protocols; D013196:Dihydrotestosterone / Q000008:administration & dosage; D004958:Estradiol / Q000008:administration & dosage / Q000502:physiology*; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D008297:Male; D011673:Pulsatile Flow; D011863:Radioimmunoassay; D013739:Testosterone / Q000502:physiology*
D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D005640:Follicle Stimulating Hormone