GPC4 (glypican-4) is involved in various growth factor signaling mechanisms. GPC4 influences cell proliferation by serving as a co-receptor for growth factor. It might regulate the Wnt signaling pathway. GPC4 might be associated with epileptic seizures, with its gene upregulated in the brain. GPC4 is an adipokine and enhances insulin signaling. Overexpression of this gene in polycystic ovary syndrome might be associated with the risk of cardiovascular disease.