Pituitary developmental gene defects and their contribution to growth hormone deficiency

Growth hormone deficiency (GHD) is a rare endocrine disorder responsible for growth failure. In the absence of an identified secondary cause, a genetic etiology can be identified, affecting genes involved in hypothalamo-pituitary growth hormone (GH) regulation or in pituitary development itself. The anterior pituitary gland arises from the oral ectoderm and is regulated by neuroectodermal signaling and transcription factors that ensure proper differentiation of hormone-producing cells. GH secretion is stimulated by growth hormone-releasing hormone (GHRH) and ghrelin, with mutations in their respective receptors (GHRHR, GHSR) contributing to isolated GHD (IGHD). Mutations in GH1, encoding GH itself, are the main genetic cause of IGHD. GHD can also arise from mutations in transcription factor genes such as POU1F1, PROP1, IGSF1 or TBX19 or in genes involved in early brain development such as GLI2, LHX3 or HESX1, potentially leading to syndromic presentations with multi-organ involvement. Understanding the genetic basis of GHD is essential to improving diagnostic strategies, genetic counseling and the development of targeted therapies. Although animal models have been fundamental for understanding pituitary ontogenesis, emerging tools such as human pituitary organoids now offer the promise of dissecting human-specific regulatory mechanisms that cannot be fully captured in traditional animal models. This review aims to provide a comprehensive overview of all known genetic causes of GHD, with a particular focus on the underlying molecular mechanisms and their associated phenotypes.