Idiopathic growth hormone deficiency: a vanishing diagnosis?

Some non-organic causes for growth hormone (GH) deficiency (GHD) can be attributed to genetic defects within the hypothalamo-pituitary axis. Using modern molecular biology techniques micromutations within the GH and GH-releasing hormone receptor genes have been detected as a rare cause of isolated GHD. Combined pituitary hormone deficiencies (CPHD), on the other hand, are associated with defects that manifest during the organogenesis of the anterior pituitary gland. In recent years an increasing number of patients with CPHD has been reported, showing mutations within pituitary transcription factors Pit-1, Prop-1 and HesX1. Such defects can be observed with different frequencies in patients. Some disorders, such as CPHD due to Pit-1 mutations, display a hormonal phenotype that seems more or less invariable. In most other forms of genetic CPHD both the combination and severity of anterior pituitary hormone deficiencies vary considerably. Ongoing research concentrates on factors involved in the differentiation and proliferation of cells that belong to the hypothalamo-pituitary growth axis. As not every possible candidate turns out to be a frequent cause of GHD or CPHD in humans, it will be many more years before the term 'idiopathic' becomes a vanishing attribute to the clinical diagnosis of pituitary insufficiency.