A secreted hormone crucial in growth control, GH1 stimulates IGF1 secretion. GH1 levels decline with age in humans and may contribute to loss of body mass [280]. Several results from model organisms, including rodents, suggest that the GH1/IGF1 axis plays a role in ageing. However, it is the attenuation of GH1/IGF1 activity that is associated with longevity in model organisms [286]. Conversely, transgenic mice overexpressing bovine GH1 are bigger than controls and may age faster [278]. In rats, moderate suppression of GH1 slightly extends lifespan while an extreme suppression leads to a shorter lifespan [287]. On the other hand, growth hormone deficiency likely diminishes lifespan in humans [144]. In spite of its controversy, GH1 is a possible candidate for a gene playing a role in human ageing. Also called somatotropin.