Hyperthyroidism and high serum levels of TSH associated with pituitary tumour

We report a 28-year-old male with persistent clinical and laboratory findings of hyperthyroidism associated with marked elevated serum levels of TSH and no response to TRH despite hemithyroidectomy and subsequent antithyroid drug therapy two years previous to admission to our hospital. Subsequent skull X-rays, CT scans and angiographic findings demonstrated the presence of a pituitary tumour. After operation and radiation therapy T3, T4 and TSH levels returned to normal values. Seven years later the patient is still euthyroid. We conclude that hyperthyroidism in our patient was due to excessive secretion of TSH by the pituitary tumour.