Thyrotropin-releasing hormone-like material in human retina

Thyrotropin-releasing hormone (TRH)-like material was found in human retina obtained at autopsy from eyes used for corneal grafts. The TRH-like material was extracted with methanol and was found to be indistinguishable from synthetic TRH in its immunoreactivity and bioreactivity and in its proteolytic degradation by fresh human serum. The TRH concentration in human retina was similar to that reported in human cerebral cortex. These data are in keeping with the notion that the retina is an extension of the central nervous system. The physiological function of human retinal TRH in unknown: probably it acts as a neurotransmitter.