Endocrine Abstracts

Introduction: TSH-secreting adenomas represent <2% of pituitary tumors. Surgery and/or radiotherapy are primary treatment options. Somatostatin analogues and also dopamine agonists, represent valuable alternatives or adjuvant therapies.

Objective: To report a case of euthyroidism and tumor stability achieved in a TSH-secreting pituitary macroadenoma, treated with octreotide-LAR, as first line therapy, and then added cabergoline. To review the efficacy of these therapeutic agents, in controlling hormone secretion and tumor shrinkage, in TSH-omas.

Clinical case: Sixty-nine year-old men; absent personal or family thyroid disease history. Physical exam: clinical hyperthyroidism and small diffuse goiter. Laboratory: rising thyroid hormones and TSH (maximum: TSH=14.1 mU/l, fT₄ =59.2 pmol/l, T₃=4.9 nmol/l); negative thyroid antibodies; other pituitary hormones were normal. Central hyperthyroidism was investigated. α-Subunit =15.5 μg/l; α-subunit/TSH molar ratio=8.1; pituitary MRI: Hardy grade II, macroadenoma, measuring 22×18×17 mm (3.53 cm³). Campimetry was normal. Methimazole used during 6.5 months to control fT₄ and thyrotoxic symptoms, corresponding with significant increase in TSH (maximum 98.1 mU/l). Patient refused surgery or radiotherapy. Octreotide-LAR 20 mg→30 mg, monthly injection, was initiated. Eleven months over the first MRI and after 8 months of therapy, follow-up MRI showed tumor stability (3.52 cm³). TSH reduction was considerable (98.1→17.5 mU/l) and fT₄ normalized (22.6 pmol/l). Aiming further hormone control and tumor reduction, we initiated cabergoline 0.5 mg twice a week and persistent euthyroidism was achieved, with no need for methimazole.

Discussion: Somatostatin analogues can control TSH, thyroid hormones and induce tumor shrinkage in ~90, 70 and 40% of TSH-omas, respectively. Dopamine agonists are less effective. Few articles report the efficiency of long acting somatostatin agonists (lanreotide and octreotide-LAR) in TSH-omas. Published data show tumor stability and equivalent efficacy of these formulations in controlling TSH and thyroid hormones. Tumor shrinkage is yet to be demonstrated with long acting analogues, but hormone control, tumor stability and treatment simplicity represent important achievements.