A 38-yr-old female with a TSH- and
GH-secreting pituitary adenoma is described, who had both overt symptoms,
hyperthyroidism and
acromegaly. Her serum TSH was not suppressed despite high concentrations of free T3 and free T4, and her alpha-subunit/TSH molar ratio was high. Her serum 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
somatostatin analog. Although she did not have
hyperprolactinemia, the in vitro culture and immunohistochemical studies revealed that the
adenoma cells produced and released PRL, in addition to
TSH, alpha-subunit 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 characteristics of somatotrophs. This case was considered to be of interest, because the
adenoma was ultrastructurally monomorphous, but immunohistochemically polymorphous.