Serum vitamin D metabolites do not change in response to intravenous injection of thyrotropin releasing hormone (TRH) and growth hormone releasing factor (GHRF 1-44) in children.

Several reports claim that thyroid hormones and growth hormone participate in the regulation of vitamin D synthesis. We investigated whether there was a direct effect of their releasing hormones on vitamin D metabolism. TRH (7 micrograms/kg) was injected iv in 8 children with euthyroid diffuse goiter and GHRF (1 microgram/kg) in 10 short normal children. TRH injection induced significant TSH elevations but no changes in serum vitamin D metabolites, calcium and phosphorus. GHRF administration resulted in marked growth hormone elevations without alterations in the serum vitamin D metabolites, calcium and phosphorus. These results indicate no direct effect of TRH or GHRF itself on vitamin D metabolism, as well as a lack of very short term effect of growth hormone and TSH.