PROP1 (Prophet of POUF1) mutations are the most frequent genetic cause of combined pituitary hormone deficiency, a condition associated with a deficiency or inadequate production of hormones of the anterior pituitary. The PROP1 gene encodes a transcription factor involved in the ontogeny, differentiation and function of somatotrophs, lactotrophs and thyrotrophs. These mutations are characterized by a remarkable clinical variability, including time of onset of hormonal deficiencies, hypophyseal dimensions and secretion of cortisol.