Hyperthyroidism, acromegaly, and hyperprolactinemia in a patient with a mature plurihormonal PIT-1 lineage adenoma

Abstract Concurrent thyrotropin (TSH) secreting and growth hormone (GH) secreting pituitary adenomas are rare entities. Although tumors of the PIT-1 lineage may coexpress TSH and GH, concurrent biologically active secretion resulting in central hyperthyroidism and acromegaly is uncommon. We report the case of a 42-year-old woman presenting with weight loss, palpitations, amenorrhea, and progressive acromegalic features. Biochemical evaluation revealed central hyperthyroidism with elevated free T4 and inappropriately normal TSH, markedly elevated insulin-like growth factor 1 (IGF-1) and GH, hyperprolactinemia, and elevated α-subunit. Pituitary magnetic resonance imaging demonstrated a 2.7-cm macroadenoma with cavernous sinus extension. She underwent transsphenoidal resection without complications. Pathology confirmed a mature plurihormonal PIT-1 lineage adenoma immunopositive for TSH, GH, and prolactin with a Ki-67 of 3%. Immediately postoperatively, thyrotoxicosis and hyperprolactinemia resolved, IGF-1 levels declined, acromegalic features improved, and menses resumed. Over the ensuing months, thyroid and prolactin tests remained within normal range, but the IGF-1 level remained elevated. This case illustrates the rare presentation of a PIT-1 lineage adenoma secreting biologically active TSH, GH, and prolactin. Comprehensive hormonal evaluation and long-term biochemical and radiologic surveillance are essential, given the risk of incomplete remission despite apparent surgical cure.