FRI292 Asymptomatic TSH Secreting Pituitary Macroadenoma

Disclosure: B. Gautam: None. M.S. Hossain: None. H. liao: None. K. Mandal: None. D.S. Rosenthal: None. S.C. Kumar: None. Introduction: TSH-producing adenoma is a rare disorder accounting for 0.5-2% of all pituitary adenomas with prevalence of 1-2 cases/million, often diagnosed at the stage of invasive macroadenoma hence challenging to manage. Case Presentation: A 36 years old male with no PMH referred to endocrine clinic for the evaluation of insomnia with abnormal thyroid panel for last 4 years. He denied skin or hair changes, diaphoresis, tremor, change in appetite, weight or bowel habits, cold/heat intolerance, palpitations, recent use of biotin or x-ray contrast exposure. Patient denied headache, visual or hearing impairment, galactorrhea, sexual dysfunction, change in facial appearance or size of gloves & shoes. Patient also denied childhood history of developmental delay, learning disability and family history of thyroid disorder. Unremarkable physical exam with normal vitals. Thyroid was normal without palpable nodule. No thyroid bruit. Normal visual field by confrontation. No tremors, gynecomastia or galactorrhea noted. Laboratory results showed normal CBC, CMP, TSH 5.2 (0.55-4.78 uIU/ml) with FT4 2.1 (0.8-1.8 ng/dl), FT3 5.4 (2.3-4.2 pg/ml), FT4 by dialysis 3.1 (0.9-2.2 ng/dl), FT3 by dialysis 433 pg/dl, Thyroglobulin ab <1 (<1 IU/ml), TPO ab 3 (<9 IU/ml), TSI <89 (<140%), TBII <1 (<2 IU/L), HAMA <6 (<74 ng/ml). Normal ACTH 17 (6-50 pg/ml), serum cortisol level 10.5 (5.2-22.4 ug/dl), prolactin 9.2 (2-18 ng/dl), GH 0.1 (<7.1 ng/ml), IGF-1 183 (53-331 ng/ml), LH 4.7 (1.5-9.3 mIU/ml), FSH 5.9 (1.6-8 mIU/ml), free testosterone 120 (35-155 pg/ml) and total testosterone 1100 (250-1100 ng/dl), SHBG 82 (10-50 nmol/L), alpha-subunit 0.8 (0.1-0.5 ng/ml) & alpha/TSH molar ratio 1.5. MRI brain with pituitary protocol showed an expansile round enhancing soft tissue mass filling the sellar cavity measuring 1.5 x 1.5 x 1.3 cm tenting the optic chiasm without cavernous sinus involvement. Patient was diagnosed with TSH secreting pituitary adenoma and referred to Neurosurgery. Patient had successful trans-sphenoidal adenectomy. Post-surgery TFTs: TSH 2.18 (0.55-4.78 uIU/ml), FT4 1.2 (0.8-1.8 ng/dl). Pathology report showed pituitary adenoma, IM stains positive for FSH, GH patchy and TSH (patchy and weak), negative for prolactin and ACTH. Rare tumor cells positive for LH Discussion: Our case highlights the importance of early diagnosis and appropriate treatment of TSH secreting adenoma to prevent complications such as hyperthyroidism, visual field defect and pan-hypopituitarism. Diagnosis in our case was particularly challenging as the patient was completely asymptomatic, therefore emphasize the importance of correlating TSH level with FT4 and early evaluation of central cause in the presence of biochemical evidence suggesting central thyroid disorder. Presentation: Friday, June 16, 2023