All of the following sho stature cases are caused by mechanisms independent of specific defects in growth hormone axis except
Correct Answer: Laron dwarfism
Description: Sho stature may also be caused by mechanisms independent of specific defects in the growth hormone axis. It is characteristic of childhood hypothyroidism (cretinism) and occurs in patients with precocious pubey. It is also pa of the syndrome of gonadal dysgenesis seen in patients who have an XO chromosomal pattern instead of an XX or XY pattern. Various bone and metabolic diseases also cause stunted growth, and in many cases there is no known cause ("constitutionally delayed growth"). Chronic abuse and neglect can also cause dwarfism in children, independent of malnutrition. This condition is known as psychosocial dwarfism or the Kaspar Hauser syndrome, named for the patient with the first repoed case. Finally, Achondroplasia, the most common form of dwarfism in humans, is characterized by sho limbs with a normal trunk. It is an autosomal dominant condition caused by a mutation in the gene that codes for fibroblast growth factor receptor 3 (FGFR3). This member of the fibroblast growth receptor family is normally expressed in cailage and the brain. In another group of dwarfed children, the plasma growth hormone concentration is normal or elevated but their growth hormone receptors are unresponsive as a result of loss-of-function mutations. The resulting condition is known as growth hormone insensitivity or Laron dwarfism. Plasma IGF-I is markedly reduced, along with IGFBP 3, which is also growth hormone-dependent.
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