Prolactin itself has been suggested to increase serum somatomedin C/IGF-I levels in patients with craniopharyngioma or pituitary tumors who exhibit normal IGF-I levels and normal-to-accelerated growth following surgery; this possibility is based on in vitro mitogenic properties of prolactin upon mammary tissue proliferation in rodents and cell division in Nb2 node lymphoma cells [4, 24, 25]. The gene discussed is IGF1; the disease is craniopharyngioma.