Reinitiation of sperm production in gonadotropin-suppressed normal men by administration of follicle-stimulating hormone

The specific roles of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in controlling human spermatogenesis are poorly understood. We studied the effect of an experimentally induced, selective LH deficiency on sperm production in normal men. After a 3-mo control period, five men received 200 mg testosterone enanthate (T) i.m./wk to suppress LH, FSH, and sperm counts. Then, while continuing T at the same dosage, human FSH (hFSH) was administered simultaneously to replace FSH activity, leaving LH activity suppressed. Four men received 100 IU hFSH s.c. daily plus T (high dosage hFSH) for 13-14 wk, while one man received 50 IU hFSH s.c. daily plus T (low dosage hFSH) for 5 mo. The effect on sperm production of the selective LH deficiency produced by hFSH plus T administration was assessed. In the four men who received the high dosage hFSH regimen, sperm counts were markedly suppressed during T administration alone (0.3+/-0.2 million/cm(3), mean+/-SE, compared with 94+/-12 million/cm(3) during the control period). Serum LH bioactivity (determined by in vitro mouse Leydig cell assay) was suppressd (140+/-7 ng/ml compared with 375+/-65 ng/ml during control period) and FSH levels (by radioimmunoassay) were reduced to undetectable levels (