Abnormal Secretion of Glycoprotein α-Subunit and Follicle-Stimulating Hormone (FSH) β-Subunit in Men with Pituitary Adenomas and FSH Hypersecretion*

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Abstract
The serum concentrations of the glycoprotein α-subunit and the FSH β-subunit were determined basally and in response to gonadotropin-releasing hormone (GnRH) in 12 men who had pituitary adenomas associated with selective hypersecretion of FSH. The same determinations were also made in men who had primary hypogonadism and serum FSH concentrations elevated to a degree similar to that of the men who had pituitary adenomas, as well as in two groups of normal men matched in age to the men with pituitary adenomas and the men with primary hypogonadism, respectively. Because intact FSH cross-reacted in the α-subunit and FSH β-subunit assays and intact LH cross-reacted in the α-subunit assay, the values for serum concentrations of both subunits were corrected for the contributions of the intact hormones. The FSH β-subunit was also determined in post-GnRH sera after separating it from intact FSH by gel filtration chromatography. The serum α-subunit response to GnRH was less in the men who had pituitary adenomas than in age-matched normal men, but was greater in the men who had primary hypogonadism than in age-matched normal men. The serum FSH β-subunit concentrations, in contrast, were significantly higher in the men who had pituitary adenomas, both basally and in response to GnRH, than in the men who had primary hypogonadism, and were not detectable at all in the two groups of normal men. Because the men who had pituitary adenomas differed in the secretion of both subunits from the men who had primary hypogonadism as well as from normal men, the association of selective FSH hypersecretion with a pituitary adenoma may represent abnormal control of FSH secretion by a gonadotroph cell adenoma.