thyroid-stimulating hormone (TSH), a substance secreted by the anterior lobe of the pituitary gland that controls the release of thyroid hormone and is necessary for the growth and function of the thyroid gland. The secretion of TSH is regulated by thyrotropin-releasing hormone, elaborated in the median eminence of the hypothalamus and circulating thyroid hormone levels. Normal adult blood levels are 2 to 10 mU/L (SI units). Also called thyrotropin. See also thyroid hormone.
