Thyrotrophin-releasing hormone: a growth hormone-releasing factor

The regulation of pituitary GH has traditionally been considered to be under dual hypothalamic control, by inhibitory and stimulatory releasing factors (SRIF and GRF respectively). The specificity of these factors is not absolute, however, and both SRIF and GRF have been implicated in the regulation of other pituitary hormones. Likewise, TRH not only regulates pituitary thyrotrophin but is also an acknowledged prolactin releasing factor. Since TRH also stimulates GH release throughout the vertebrates, it should also be considered as a GRF.