TSH-Secreting Pituitary Tumors

TSH-secreting pituitary tumors represent one major group of the syndrome of inappropriate secretion of TSH (1). This syndrome is defined as inappropriately measurable or elevated concentrations of TSH in the presence of increased total and free serum thyroid hormones, and is comprised of both neoplastic and non-neoplastic variants. Neoplastic TSH production by a pituitary tumor may occur in the setting of either a microadenoma or macroadenoma and may be associated with the production of other hormones, particularly growth hormone and prolactin. Because of increased awareness of physicians, these tumors are being recognized with increasing frequency. Currently, over 40 cases have been reported in the literature, and we have seen or are aware of several additional unreported cases.