Octreotide normalizes thyroid function tests in a pregnant woman with a thyrotropin-secreting adenoma

Thyrotropin-secreting pituitary tumors are rare causes of hyperthyroidism. We present a case complicated by pregnancy, which made diagnosis and treatment options less straightforward. A 32-year-old female with a history of palpitations was found to have hyperthyroidism. Her family history was positive for Graves disease, and her thyroid was symmetrically enlarged, without palpable nodules. Free T4 and free T3 were elevated, with normal thyrotropin-secreting hormone (TSH). No heterophilic antibody interference with TSH assay was found, and no other family members had thyroid resistance. TR-β gene sequencing was negative. Thyroid ultrasound showed a thyroid nodule in the left lobe, which was benign by biopsy. Radioiodine scan showed homogeneous uptake of 41% at 24 hours. Thyroid antibodies were normal. MRI suggested a pituitary microadenoma, but sex hormone binding globulin and α subunit were normal. A subcutaneous dose of 0.1 mg of octreotide normalized TSH within 6 hours. She was treated with octreotide for 3 months. Free T4 and TSH remained normal until 6 weeks postpartum, when hyperthyroidism recurred. This is the third reported case of a TSH-secreting tumor in a pregnant woman that went into remission during pregnancy. This case demonstrates the utility of octreotide for diagnosis and treatment of pituitary hyperthyroidism and that hyperthyroidism caused by a TSH-secreting pituitary adenoma can remit during pregnancy.