Growth disorders caused by genetic defects in the growth hormone pathway.

The growth hormone (GH) pathway is composed of a series of interdependent genes whose products are required for normal growth (Fig 1). The GH pathway genes include ligands (GH and insulin-like growth factor 1 [lGF-1]), transcription factors (prophet of pit 1, or prop 1 and pit 1), agonists and antagonists (growth hormone-releasing hormone [GHRH] and somatostatin), and receptors (GHRH receptor [GHRHR] and the GH receptor [GHR]). These genes are expressed in different organs and tissues, including the hypothalamus, pituitary, liver, and bone. Effective and regulated expression of the growth hormone pathway is essential for growth in stature as well as homeostasis of carbohydrate, protein, and fat metabolism.