A Rare Cause of Hypothyroidism: TSH oma

TSH (tyrotiropin) secreting pituitary adenomas account for <1% of all hypophyseal adenomas with a prevelance of 1/1.000.000 and is a very rare reason of hyperthyroidism (TSH oma). In these casess free t4 and free t3 levels are elevated whereas TSH levels are normal or elevated. A 26 year old women referred to our outpatient clinic with complaints of palpitation, tremors, weight loss and dispnea for three months. Laboratory analysis showed that plasm free T3 levels (8,2 mIU/ml-normal 3,2-5,4 ) and TSH levels were high(5,7 mIU/ml, normal 0,3-4,9 mIU/ml), and free T4 level was on the upper limit (14,7 mIU/ml- normal 9-15 mIU/ml). Considering TSH depended hyperthyrodism the patient went under a magnetic resonance imaging scan (MRI) which confirmed an 11 mm lesion on hypophysis which was compatible with adenoma.The patient was diagnosed with TSH oma and went under transnasal, transsphenoidal hypophysis surgery. Although TSH secreting pituitary adenomas are rare causes of hyperthyrodism, advanced laboratory methods allow them to be diagnosed early and avoid unnecessary tests and time loss. [Cukurova Med J 2013; 38(3.000): 499-502]