Hypophyse

Abstract

Ante- and post-hypophysis are the two constituents of the hypophysis. The ante-hypophysis synthesizes and secretes mainly the growth hormone, thyrotropin, prolactin, adrenocorticotropic hormones and the gonadotrophins. The vasopressin and oxytocin hormones are secreted by the post-hypophysis. The hypophysis development and differentiation are controlled by a chain of different factors that involve numerous signalisation genes from adjacent structures, in addition to specific transcription factors, to date insufficiently known. The regulation and mode of action of the various hormones are now well identified. Activating and inhibiting hormones synthesized in the hypothalamus regulate the functioning of ante-hypophysis cells. They act through specific cellular receptors. In children, hypothalamus-hypophysis hypofunction is far more frequently observed than hyperfunction. Hypopituitarisms are serious diseases which, if untreated, may have irreversible consequences such as severe nanism in case of somatotropic insufficiency, mental retardation in case of thyrotropic insufficiency, lack of puberty development and sterility in case of gonadotropic insufficiency, and even death in case of corticotropic insufficiency. The diagnosis of hypophysis insufficiency is based on clinical data, and results of functional investigations, and brain magnetic resonance imaging. Treatments are substitutive, given for life, and concerned patients necessitate lifelong medical management. Hypophysis insufficiency may be either isolated or multiple, either acquired (mainly in relation with a tumoral or infiltrative process in the hypothalamus-hypophysis area), or congenital. Various types of human congenital insufficiency (isolated or combined) due to a genetic cause have been described these last years. However, the molecular mechanisms that produce the major part of genetic hypopituitarisms remain to be elucidated.