The nature of the LH abnormality in four men who had gonadotroph cell pituitary adenomas was studied to determine why they had supranormal serum LH concentrations but subnormal or normal serum testosterone concentrations. When basal sera from these four men were subjected to gel filtration chromatography, FSH immunoreactivity eluted principally in the position of intact FSH, but the elution patterns of LH immunoreactivity were biphasic; one peak corresponded to intact LH, and another peak corresponded to the LH subunits, LH beta and alpha. Gel filtration of sera obtained after administration of TRH showed increases in LH immunoreactivity predominantly in the subunits peak. The subunits peak in basal sera consisted principally of alpha, but the percent increase in LH beta in post-TRH sera was greater. When dispersed cells from one gonadotroph adenoma were cultured, medium LH immunoreactivity eluted with the LH subunits. LH beta release into the medium was somewhat greater than alpha initially, but declined more rapidly. We conclude that the apparent hypersecretion of immunoreactive LH of impaired biological activity by four men with gonadotroph cell adenomas represents hypersecretion of LH beta- and alpha-subunits that are uncombined, perhaps because of a structural abnormality or anatomical compartmentalization.