MON-313 Thyrotropin-Secreting Pituitary Tumors: Clinical Features, Diagnostic Criteria and Treatment Outcomes in 28 Patients

Introduction Thyrotropin-secreting pituitary adenoma (TSH-oma) is a rare cause of thyrotoxicosis and represents 0.5-3% of all pituitary adenomas. Given the rarity of the disease and the lack of extensive clinical experience in world practice, the analysis of each case of TSH-secreting pituitary tumors is extremely relevant. Materials and methods: We enrolled consecutive patients with TSH secreting pituitary adenoma. TSH (0,25-3,5 mIU/L), FT4 (9-20 pmol/l) FT3 (2,5-5,5 pmol/l) were measured by Architect i2000SR (Abbott Laboratories, Abbott Park, Illinois, U.S.A). An octreotide test consisted of injecting short-acting somatostatin analogue (SSA) at a dose of 100 μg 3 times a day subcutaneously during 3 days or long-acting SSA 20 mg in 28 days minimum for two months and measuring thyroid profile blood tests before and at the end of the test. MRI was performed on GE Optima MR450w 1.5T. Results: We present 28 case series with TSH-omas followed in our center from 2010 to 2019, the median age - 46 (from 10 to 71 years) with a predominance of a female (21 cases) over a male (7 cases). Clinical manifestations included cardiac arrhythmias (82.1%), neurological changes (60.7%), visual impairment (39.3%), osteoporosis (28.6%), hypopituitarism (7.1%). At first admission, 17 patients had increased TSH, FT3 and FT4; in 7 patients - FT3 and FT4 only, and in 4 - an increase was in one of the hormones; mean value of TSH was 5,04 mIU/L, FT4 - 24,46 pmol/l, FT3 - 8,9 pmol/l. SSBG, CTx, osteocalcin were elevated in 60.9%, 57.9% and 31.6% of cases, respectively. In 88.5% of cases octreotide test led to thyroid hormones normalization. On MRI macroadenomas was registered in 67.9%. In 12 patients, diagnosis was confirmed by immunohistochemical examination. In 12 patients, the diagnosis verification was based on remission after surgical and medical treatment. In the remaining four cases, the diagnosis was made on clinical and laboratory data, however, confirmation was inconceivable due to inefficacy of medical treatment. Remission was achieved in 23 patients: 17 of 21 after neurosurgery (81%), 3 of 7 after primary administration of SSA, and 3 after administration of SSA after surgery (100% remission in cases of combined treatment and 42.9% of monotherapy); 3 out of 5 patients who did not achieve remission were lost for observation. Two patients died: in one case due to the brain herniation and cachexia in active thyrotoxicosis. In second case, the patient developed a mental disorder (catatonia) after the second transphenoidal adenomectomy, which led to death. Conclusion The diagnosis of TSH-oma should be based on all thyroid hormones assessment, since biochemical thyrotoxicosis can manifest itself in various ways. The most effective treatment is transphenoidal adenomectomy. If a neurosurgery is not effective or contraindicative, preoperative preparations SSA can be used.