Isolated growth hormone deficiency type IA

Isolated growth hormone deficiency type IA (IGHD IA) is the most severe form of isolated growth hormone deficiency, caused by complete absence of growth hormone (GH) production. It is also known as growth hormone deficiency due to GH1 gene deletion or Illig-type growth hormone deficiency. The condition results from homozygous deletions or severe loss-of-function mutations in the GH1 gene located on chromosome 17q23.3, which encodes the growth hormone protein. Because no endogenous GH is produced, affected individuals have no immunological tolerance to GH, which has important implications for treatment. Infants with IGHD IA may present with hypoglycemia in the neonatal period and typically show severe growth failure becoming apparent in the first six months of life. Affected children demonstrate markedly short stature, with length falling progressively below normal growth curves. Other features may include a prominent forehead, midfacial hypoplasia (underdevelopment of the midface), truncal obesity, and a high-pitched voice. Micropenis may be observed in affected males. The skeletal system is significantly affected, with delayed bone maturation. Treatment involves recombinant human growth hormone (rhGH) replacement therapy; however, a major clinical challenge in IGHD IA is that patients frequently develop high titers of anti-GH antibodies upon exposure to exogenous GH, since their immune system has never been exposed to the protein. These antibodies can neutralize the therapeutic effect of GH, leading to growth deceleration after an initial response. In cases where antibody formation renders GH therapy ineffective, alternative approaches such as recombinant IGF-1 (mecasermin) therapy may be considered, as IGF-1 acts downstream of GH to promote growth. Early diagnosis and careful monitoring of treatment response and antibody levels are essential for optimal management.

Common questions about Isolated growth hormone deficiency type IA