Inappropriate Secretion of Thyrotropin: Discordance between the Suppressive Effects of Corticosteroids and Thyroid Hormone*

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Abstract
A 46-yr-old postmenopausal woman with acromegaly and hyperthyroidism had serum levels of TSH which were repeatedly measurable (2.0-3.4 μU/ml) and, therefore, inappropriately elevated. In addition, serum concentrations of the α-subunit were persistently elevated (10.7-18.8 ng/ml). Although there was a reciprocal relationship between serum T4 and TSH levels during treatment with antithyroid drugs, the concentration of α-subunit did not appear to vary with either T4 or TSH. Transsphenoidal surgery documented the presence of a pituitary adenoma but failed to cure either the acromegaly or the hyperthyroidism. While she was hyperthyroid, α-subunit fell to 40 μU/ml, increased α-subunit from 14.6 to 21.8 ng/ml, and increased GH from 9 to 25 ng/ml. The patient was subsequently treated with both pituitary irradiation and 131I. Eighteen months later, she was euthyroid with serum TSH levels of 1.0 μU/ml, α-subunit levels of 4.3 ng/ml, and GH levels of 9 ng/ml. These data indicate that the patient had a pituitary tumor that secreted GH, TSH, and α-subunit and that there was a discordance between the feedback inhibitory effects of glucocorticoids and T3 on TSH secretion, and suggest that the tumor had an altered receptor for thyroid hormone. (J Clin Endocrinol Metab48: 700, 1979)

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