Hyperthyroidism and acromegaly caused by a pituitary TSH- and GH-secreting tumour

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Abstract
A female patient with acromegaly, TSH-induced hyperthyroidism and a large eosinophilic pituitary adenoma is reported. Granules in the adenoma cells were shown by immunohistochemical methods to contain GH and with monoclonal TSH-antibodies it was shown that 5-10% of the cells secreted TSH. The basal serum TSH was elevated in the hyperthyroid phases and was not suppressible by exogenous T3 [triiodothyronine] but decreased markedly with dexamethasone. There was a small subnormal rise in serum TSH after TRH injection which was totally suppressed by T3 (but not dexamethasone). L-dopa, bromocriptine and somatostatin caused a 20-30% decrease in serum TSH. The .alpha.-subunit concentration was also elevated and was equally depressed by bromocriptine and somatostatin. The urinary excretion of TRH was within reference limits. This mixed tumor obviously secreted an excess of GH and TSH causing acromegaly and hyperthyroidism.