A FUNCTIONAL THYROTROPIN-SECRETING AND GROWTH HORMONE-SECRETING PITUITARY-ADENOMA WITH A ULTRASTRUCTURALLY MONOMORPHIC FEATURE - A CASE-STUDY

A 38-yr-old female with a TSH-and GH-secreting pituitary adenoma is de scribed, who had both overt symptoms, hyperthyroidism and acromegaly. Her serum TSH was not suppressed despite high concentrations of free T 3 and free T4, and her alpha-subunit/TSH molar ratio was high. Her ser um GH was consistently high, and was not suppressed by an oral glucose tolerance test. Preoperative testing revealed that, although the TSH response was impaired, TSH, alpha-subunit and GH were increased by TRH injection, and that these hormones were reduced by bromocriptine or s omatostatin analog. Although she did not have hyperprolactinemia, the in vitro culture and immunohistochemical studies revealed that the ade noma cells produced and released PRL, in addition to TSH, alpha-subuni t and GH. Immunohistochemical studies showed the presence of GH in the cytoplasm of many adenoma cells. TSH beta-positive adenoma cells were less frequently seen than GH-positive adenoma cells. No cells showed the coexistence of GH and TSH beta, and a few cells were positive for PRL. By electron microscopy, the adenoma was found to be composed of a single cell type resembling thyrotrophs, and did not have any charact eristics of somatotrophs. This case was considered to be of interest, because the adenoma was ultrastructurally monomorphous, but immunohist ochemically polymorphous.