title: Androgen effects on bioactive and immunoreactive gonadotrophin levels during puberty in male baboons.
abstract: The effect of androgens on changes in circulating LH and FSH during pubertal development was examined longitudinally in a 3 year study in male hamadryas baboons. Baboon LH and FSH were measured by a species-specific radioimmunoassay and bioactive LH (B-LH) was measured by the mouse in vitro Leydig cell bioassay. Control baboons (n = 5) progressed normally through puberty. Eight baboons were castrated prepubertally; of these four received testosterone implants at the chronological age (CA) of clinical puberty (4.0 +/- 0.1 yr, mean +/- SEM). The timing of the postcastration rise in B-LH levels ranged between 1 and 15 months later (median 3.5 months) (CA 3.5 +/- 0.2 yr) thus supporting the hypothesis that central activation of gonadotrophins occurs at the time of puberty, independent of gonadal influences. Similar results were seen for immunoreactive-LH (IR-LH) and IR-FSH levels. IR- and B-LH levels continued to rise with age (P < 0.0003) in the untreated castrated baboons, associated with an increased LH B/I ratio. Administration of testosterone resulted in temporary suppression of B-LH, IR-LH and IR-FSH levels; however gonadotrophin levels subsequently rose with age despite increased testosterone levels. Thus the mechanisms initiating puberty involve both gonad-independent events as well as alterations in negative androgenic feedback sensitivity on gonadotrophin secretion.
authors.affiliation: Department of Medicine, University of Sydney, Australia.
authors.forename: B A
authors.initials: BA
authors.lastname: Crawford
authors.forename: J
authors.initials: J
authors.lastname: Spaliviero
authors.forename: J
authors.initials: J
authors.lastname: Simpson
authors.forename: D J
authors.initials: DJ
authors.lastname: Handelsman
mesh_terms: D000818:Animals; D001681:Biological Assay; D004343:Drug Implants; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007985:Leydig Cells / Q000187:drug effects; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D051379:Mice; D009919:Orchiectomy; D010215:Papio / Q000097:blood / Q000254:growth & development*; D011863:Radioimmunoassay; D012741:Sexual Maturation; D013739:Testosterone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D015430:Weight Gain
chemical_list: D004343:Drug Implants; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone