PIT-1 is an important transcription factor for the control of GH, PRL and TSH expression in the somatotroph, lactotroph and thyrotroph cells of the anterior pituitary gland respectively, and mutations on the PIT-1 gene cause congenital GH, PRL, and TSH deficiency. The gene discussed is PRL; the disease is hyperinsulinemic hypoglycemia, familial, 4.