The Journal of clinical endocrinology and metabolism
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J. Clin. Endocrinol. Metab. · Sep 1993
Comparative StudyA comparison between the diagnostic value of gonadotropins, alpha-subunit, and chromogranin-A and their response to thyrotropin-releasing hormone in clinically nonfunctioning, alpha-subunit-secreting, and gonadotroph pituitary adenomas.
We tested the hypothesis of whether chromogranin-A (CGA), an immunohistochemical marker of neuroendocrine tumors, could serve as a serum marker for clinically nonfunctioning pituitary adenomas. Basal and TRH-stimulated concentrations of LH, FSH, alpha-subunit, and CGA were measured in 22 patients with clinically nonfunctioning pituitary adenomas and in 20 control patients with other pituitary tumors. The control group consisted of 9 patients with PRL- and/or GH-secreting adenomas and 11 patients with nonendocrine tumors [5 craniopharyngiomas, 2 (dys)germinomas, 1 astrocytoma, 1 meningioma, 1 neurinoma of the acoustic nerve, and 1 dermoid cyst]. ⋯ Significant increases in serum gonadotropin and/or alpha-subunit levels in response to TRH occurred in 14 of 21 patients with clinically nonfunctioning adenomas and in 13 of 20 control patients. A significant CGA peak after TRH administration was demonstrated in 6 patients with clinically nonfunctioning pituitary tumors and in none of the controls. We conclude that 1) immunohistochemical staining for CGA is an excellent tool to prove the endocrine origin of clinically nonfunctioning pituitary tumors; 2) in vivo, the gonadotroph origin can be recognized in only a minority of patients who have elevated basal levels of LH, FSH, or alpha-subunit; 3) examination of the effect of TRH on CGA release is a rather insensitive, but specific, diagnostic test, allowing differentiation from nonendocrine pituitary tumors; and 4) the responses of gonadotropins and alpha-subunit to TRH, although more sensitive, are not specific for clinically nonfunctioning pituitary adenomas and are probably only reliable in cases of total hypopituitarism.