ANDROGEN EFFECTS ON BIOACTIVE AND IMMUNOREACTIVE GONADOTROPIN-LEVELS DURING PUBERTY IN MALE BABOONS

The effect of androgens on changes in circulating LH and FSH during pu bertal development was examined longitudinally in a 3 year study in ma le hamadryas baboons. Baboon LH and FSH were measured by a species-spe cific radioimmunoassay and bioactive LH (B-LH) was measured by the mou se in vitro Leydig cell bioassay, Control baboons (n = 5) progressed n ormally through puberty, Eight baboons were castrated prepubertally; o f 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 hypo thesis 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 c ontinued to rise with age (P < 0.0003) ire the untreated castrated bab oons, associated with aln increased LH B/I ratio, Administration of te stosterone resulted in temporary suppression of B-LH, IR-LH and IR-FSH levels; however gonadotrophin levels subsequently rose with age despi te increased testosterone levels, Thus the mechanisms initiating puber ty involve both gonad-independent events as well as alterations in neg ative androgenic feedback sensitivity on gonadotrophin secretion.