 Thyrotropin releasing hormone TRH is a neuropeptide used in the diagnostic evaluation of patients with dysfunction of the hypothalamic-pituitary-thyroid HPT axis. In healthy individuals, administration of TRH intravenously results in pituitary secretion of thyrotropin thyroid-stimulating hormone TSH, which in turn stimulates the thyroid gland release of thyroid hormones; thyroxine T4 and triiodothyronine T3. TRH stimulates the secretion of other pituitary hormones under normal physiologic as well as pathologic conditions. 