Increased release of insulin from pancreas
Increased release of IGF-1 from liver
Increased release of IGF-1 from hypothalamus
Defective growth hormone receptors
Ans. B. Increased release of IGF-1 from liver
Explanation: Growth hormone is a 191 -amino-acid hormone secreted from the anterior pituitary. Growth hormone increases linear growth-growth of the long bones- through increased production of insulin-like growth factor-1 (IGF-1) from the liver. IGF-1 causes bone growth by stimulating the proliferation of cartilage in bone cells. Alternatively, if there is excess growth hormone before the closure of the epiphysis, it is called “gigantism,” a condition characterized by tall stature and long limbs; after the closure of the epiphysis, the condition is called “acromegaly.” Although gigantism and acromegaly are caused by the same excess hormone, the symptoms are not alike. This patient is young enough that we can be sure that his epiphyses are not yet closed. It is unlikely that this patient is “just a tall kid” because his parents are of average height and he has long limbs; you should suspect gigantism.