TSH-producing adenomas are rare but often large and locally invasive when they occur. Pts present with goiter and hyperthyroidism, and/or sella mass effects. Diagnosis is based on elevated serum free T₄ levels in the setting of inappropriately normal or high TSH secretion and MRI evidence of a pituitary adenoma. Surgery is indicated and is usually followed by somatostatin analogue therapy to treat residual tumor. Somatostatin analogue therapy (see above) leads to normalization of TSH and euthyroidism in most and tumor shrinkage in 50-75% of pts. If necessary, thyroid ablation or antithyroid drugs can be used to reduce thyroid hormone levels.