Feedback control of FSH in the male: role of oestrogen

Serum follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured by radioimmunoassay in a group of elderly men following castration and estrogen therapy. Prior to orchiectomy, mean serum concentrations of LH and FSH were within the normal range. Two days following castration, serum LH concentrations increased in all 8 patients; higher levels of LH were subsequently measured in all but 1 patient after periods of time ranging from 49 to 210 days. Serum FSH levels, measured in 3 patients following castration, increased in a pattern parallel to LH changes. Ethinyl estradiol (EOe) in doses ranging from 5 to 300 μg/day was administered to 10 men who had been castrated 3 to 72 mth earlier. Estrogen treatment suppressed both LH and FSH in a parallel manner in 9 of 10 patients. LH was first suppressed to intact levels in 1 of 8 patients treated with 20 μg/day of EOe, in 2 of 6 patients treated with 50 μg/day, and in 1 patient by 80 μg/day. FSH was not suppressed to precastration levels until 50 μg/day of EOe was administered; this dose suppressed 3 of 6 patients. Higher doses of EOe (150-300 μg/day) suppressed both LH and FSH to levels below the sensitivity of the assay. These data fail to demonstrate any differential effect of estrogen on LH and FSH release.