Growth hormone (GH) is essential for normal growth. However, cases of normal growth without GH may occur. The mechanism of growth without GH remains still unclear. However, regarding normal growth without GH arising after brain surgery, hypothalamic damage caused by the brain surgery is thought to induce obesity, and the resulting hyperinsulinemia and/or hyperprolactinemia are assumed to be important mechanisms of normal growth without GH in postsurgery patients. It is assumed that elevated insulin and/or prolactin concentration normalize IGF-1 levels even in GHD patients, restricts the increase in serum levels of IGFBP-3, and changes the distribution of circulating IGF-1. Thus, normal growth without GH continues because of the effects of IFG-I, which are independent of GH. {xref="PMID:28443260"}