Secretion of Uncombined Subunits of Luteinizing Hormone by Gonadotroph Cell Adenomas*

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Abstract
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, LHβ and α. 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 a, but the percent increase in LHβ in post-TRH sera was greater. When dispersed cells from one gonadotroph adenoma were cultured, medium LH immunoreactivity eluted with the LH subunits. LHβ release into the medium was somewhat greater than a 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 β-and α-subunits that are uncombined, perhaps because of a structural abnormality or anatomical compartmentalization.

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