Distribution of Thyrotropin-Releasing Hormone in Human Brain

Abstract

Since the extra-hypothalamic distribution of TRH[thyrotropin-releasing hormone] in the human brain is not well established, studies were carried out in the post-mortem human brain to determine its regional concentration. The highest concentration of TRH was found in the stalk median eminence (SME), which corresponds to the median basal hypothalamus, ranging from 670-11,444 pg/mg of protein(5417 .+-. 2519 pg/mg). The next highest concentration was in the olfactory trigone, with a range of 82-9902 pg/mg of protein (2605 .+-. 2433 pg/mg), but this is by virtue of isolated, highly elevated TRH content in this area in 1 patient. A more consistent relatively high concentration was assayed in the mammillary bodies from 417-4630 pg/mg of protein(1984 .+-. 1003 pg/mg. In 1 patient in whom thalamic content of TRH was measured, 1032 pg/mg of protein was found in the lateral region, compared to 1793 pg/mg of protein in the dorsomedial area. Posterior pituitary TRH content ranged from 179-1667 pg/mg of protein. The rest of the tissues examined showed generally lower concentrations of this hormone. TRH in ventricular fluid was undetectable in 1 patient. The demonstration of TRH in various sites of the human brain suggests other non-hormonal role(s) for this tripeptide material, perhaps as a putative neurotransmitter.