Gh Need Info

Growth hormone release from the anterior pituitary is under the control of two hypothalamic hormones.

GHRH acts to stimulate release of GH while somatostatin acts to inhibit release of GH.

GH exerts its effects directly and also indirectly through insulin-like growth factors (IGFs) 1 and 2. The effects include promotion of growth of bone, soft tissue and viscera as well as having affects on protein synthesis, lipolysis and glucose transport and metabolism. IGF1 provides negative feedback to the pituitary and hypothalamus.

Other factors affecting GHRH and somatostatin secretion include sleep, exercise, stress and blood glucose levels. Oestradiol also acts to increase sensitivity of tissues to GH.

What can go wrong

A GH secreting tumour may be present in the pituitary gland leading to excessive height due to extra GH during childhood. Excessive production of GH in adulthood,after the growing ends of the bones have fused, leads to the condition of acromegaly and this can be seen as enlarged feet, hands and jaw caused by thickening of the bones as well as thickening of the soft tissue.

Insulin resistance also develops, due to downregulation of the insulin receptors caused by increased insulin production in response to increase glucose concentrations. This gives the symptoms of diabetes mellitus. Treatment of acromegaly is usually surgery to remove the tumour. The dopamine agonist bromocriptone is sometimes administered and somatostatin analogues may also be used.

Hyposecretion if GH in childhood leads to pituitary dwarfism and a characteristic fat distribution concentrated around the face and abdomen caused by a loss of metabolic function.This may be due to a number of reasons, for example irradiation of the hypothalamo-pituitary area, surgery of the pituitary gland or trauma severing the link between hypothalamus and pituitary gland, which result in lack of hypothalamic or pituitary hormone secretion. The syndrome of hypopituitarism and the importance of GH in adults has only recently been recognised. Symptoms of lack of GH include increased abdominal adiposity, reduced strength and exercise capacity, reduced bone density, elevated cholesterol and impaired psychological well-being. GH deficiency in both adults and children can be treated successfully using recombinant human GH.