A case of pituitary adenoma with possible simultaneous secretion of thyrotropin and follicle-stimulating hormone

A TSH- and FSH-screening pituitary adenoma was demonstrated in a 23-yr-old man who presented with bitemporal hemianopsia, but without clinical or laboratory evidences of hyper- or hypothyroidism or hypogonadism. Basal TSH (29-45 microunits/ml) and FSH (44-63 mIU/ml) were moderately elevated. GH and ACTH secretion were impaired, and basal PRL and testosterone were normal. TRH and LRH elicited a significant increase in TSH and FSH, respectively. The plasma glycoprotein alpha-subunit concentration was normal, and its response to simultaneous administration of TRH and LRH was low. Plasma TSH was not suppressed completely by exogenous T3. After operation and radiotherapy, elevated TSH and FSH as well as failure of T3 to suppress TSH were corrected. No significant changes in thyroid hormone concentration in the blood were detected in spite of the reduction of TSH. TSH and FSH concentrations in the tumor extract were lower than those in normal pituitaries. Histologically, the tumor was very vascular and consisted mostly of a single type of cell. The tumor cells were positively stained for FSH beta-subunit by immunohistochemical study, but for none of other pituitary hormones or subunits examined. Electron microscopic examination revealed relatively abundant single type secretory granules of high electron density. It is possible that the tumor simultaneously secreted TSH and FSH, the former possibly being immunologically active, but biologically inactive.