Unusual Association Between a Thyrotropin-Secreting Pituitary Adenoma and a Papillary Thyroid Carcinoma

Abstract

We report here an unusual case of association between thyrotropin (TSH)-secreting pituitary adenoma and papillary thyroid carcinoma in a young female patient. Serum TSH levels did not significantly change after both stimulatory (thyrotropin-releasing hormone [TRH], domperidone) and inhibitory (bromocriptine levotriiodothyronine, [LT₃], levothyroxine [LT₄], LT₄ plus LT₃) tests, while a 67% decrease of serum TSH levels was obtained after acute administration of a somatostatin analog (SMS 201-995, 100 μg sc). Serum α-subunit levels and the α-subunit/TSH molar ratio were clearly elevated. Magnetic resonance imaging (MRI) revealed the presence of a pituitary adenoma (1 cm in diameter). Pitfalls arising from the failure to inhibit TSH secretion in a patient thyroidectomized for papillary cancer are discussed.