MON-061 Overcoming Diagnostic Barriers in Thyrotropin-Secreting Pituitary Adenoma: A Case of Post-Thyroidectomy Hypothyroidism

Abstract Disclosure: K.K. Dargan: None. W. White: None. Thyrotropin-secreting pituitary adenomas (TSHomas) are a rare subtype of pituitary adenomas that present as central hyperthyroidism due to unregulated thyrotropin (thyroid-stimulating hormone; TSH) secretion. This case report highlights a unique presentation of a TSHoma with persistent hypothyroid symptoms prior to and following a total thyroidectomy. Our patient had a history of thyroidectomy for a benign multinodular goiter and a nonfunctional pituitary macroadenoma, who presented with significant weight gain, fatigue, and persistent hypothyroid symptoms despite increasing doses of thyroid hormone replacement therapy. Initial tests confirmed elevated TSH levels, elevated free T4, and subsequent evaluation demonstrated mildly elevated alpha-subunit levels. Imaging confirmed a stable pituitary macroadenoma. Suspecting a thyrotropin-secreting pituitary adenoma, she underwent transsphenoidal resection, which confirmed the diagnosis. Postoperatively, her TSH normalized, though hypothyroid symptoms persisted. TSHomas, though rare, should be considered in patients presenting with unexplained thyroid dysfunction, particularly when accompanied by pituitary abnormalities. Presentation: Monday, July 14, 2025