Fast evolution of growth hormone receptor in primates and ruminants

Pituitary growth hormone (GH) evolves very slowly in most of mammals, but the evolutionary rates ap- pear to have increased markedly on two occasions during the evolution of primates and ruminants. To investigate the evo- lutionary pattern of growth hormone receptor (GHR), we sequenced the extracellular domain of GHR genes from four primate species. Our results suggested that GHR in mammal also shows an episodic evolutionary pattern, which is consis- tent with that observed in pituitary growth hormone. Fur- ther analysis suggested that this pattern of rapid evolution observed in primates and ruminants is likely the result of coevolution between pituitary growth hormone and its re- ceptor.