SAT-LB55 A Case of Central Hyperthyroidism From a TSH Secreting Pituitary Adenoma

This is a case of a 41 year old Filipino female, with one month history of palpitations, unintentional weight loss and increased frequency of bowel movement. Patient was tachycardic and had a slightly enlarged thyroid on physical exam. There were no cushingoid or acromegalic features. Initial work-up revealed elevated TSH 7.10 U/mL prompting referral to an endocrinologist who had an initial consideration of central hyperthyroidism, MRI was done revealing a pituitary adenoma with dimensions of 7.4 x 11 x 5.8 mm. Prolactin level was at 118.9 ng/mL, gonadotropins (FSH 5 mIU/mL, LH 4.3 IU/L) were within normal range for pre-menopausal non pregnant women and early 24h urine cortisol was within normal at 63.79 nmol/ day. Patient was started on propranolol 40 mg thrice daily and methimazole 20 mg twice a day which prompted slight relief. She was also referred to neurosurgery service for further management. Patient underwent transsphenoidal surgery which was tolerated well. Subsequent clinical course revealed improvement of hyperthyroid symptoms with no evidence of post-operative complications such as hematomas, CSF leak, vision loss, diabetes insipidus or central adrenal insufficiency. Immunohistochemical staining was positive for TSH. On outpatient follow-up, repeat thyroid function tests were within normal with TSH 1.260 and free T4 15.07 pmol/L. Patient is currently symptom free and off methimazole or propranolol. Future plans include a repeat MRI after 6 months of surgery and hormonal testing to confirm cure.