IGF1 and Growth delay: Hu et al. [31] also found that GHRH, GH, and IGF-1 in serum of growth retardation yak caused by nutrient deficiency showed a significant positive correlation with body weight, and cysteamine (somatostatin inhibitor) could increase the concentration of GHRH, GH, and IGF-1 in serum of growth retardation yak, thus promoting growth.