To assess the dynamics of the suppression and recovery of plasma gonadotropins and sex steroids during and after inhibition of pituitary-ovarian function by a long-acting agonist GnRH-analog (GnRH-A), eight patients with polycystic ovarian disease were treated with 12 micrograms/kg X day GnRH-A for 56 consecutive days. In response to GnRH-A, these patients had a sharp and pronounced decline of their initially elevated immunoreactive LH and bioactive LH (bioLH) levels. Plasma immunoreactive FSH levels declined more rapidly than did bioLH, but the FSH decline was less sustained. Plasma testosterone, androstenedione, and estrone (E1) levels also declined during GnRH-A administration. The pattern of plasma androgen decrease resembled that of bioLH. There was a positive correlation between bioLH and the two androgens (r = 0.85; P less than 0.05, by Spearman's rank correlation, for both hormones). Cessation of GnRH-A administration was followed by prompt progressive increases in gonadotropin and androgen concentrations to pretreatment values. FSH recovered faster than bioLH. BioLH plasma concentrations reached pretreatment values by day 28. The recovery of plasma androstenedione and testosterone levels correlated positively with that of bioLH. Although plasma E1 levels were higher during the recovery period than during treatment, they never reached the concentrations found during the basal period, whereas estradiol concentrations were slightly but not significantly higher than those in the basal period. As a consequence, the E1 to estradiol ratio, very high in the basal period, approximated unity during recovery. These data indicate that hyperandrogenism in polycystic ovarian disease is gonadotropin dependent and accompanied by a relative abundance of LH bioactivity basally and during GnRH-A administration. Thus, the relative increase in bioLH secretion appears to be independent of the rate of gonadotropin secretion and the circulating sex steroid concentrations.