Thyrotropin-Releasing Hormone

The modern era of neuroendocrinology was ushered in just over a decade ago with the isolation and characterization, from ovine1 and porcine2 hypothalamic tissue, of a tripeptide (pyroglutamyl-histidyl-proline amide), which was designated thyrotropin-releasing hormone (TRH) by virtue of its capacity to stimulate the release of thyroid-stimulating hormone (TSH) from the mammalian anterior pituitary. Later, it was found that TRH was equally effective in stimulating prolactin secretion from the normal pituitary gland.3 Although the importance of this hypothalamic releasing factor in the regulation of the pituitary-thyroid axis in human beings and other mammals has been established,4 most studies do not accord . . .