Paediatrics: Growth hormone deficiency: management

Growth hormone deficiency: management

GH deficiency is treated with rhGH, which is administered as a once daily SC injection (0.7–1.0mg/m²/day or 23–39microgram/kg/day).

·  Treatment should be undertaken in experienced centres.

·  Responses to treatment (height velocity increase) and dose adjustments should be reviewed once every 6mths.

·  Catch up growth optimal if GH therapy is started as early as possible.

Transition to GH deficiency care in adulthood

Treatment with rhGH is continued until final adult height is achieved. At this point the GH deficiency should be reconfirmed, particularly in those with isolated or so-called idiopathic GH deficiency where the cause is unclear. Up to 50% of patients with the latter may have normal GH secre-tion when retested in early adulthood. Those patients with persisting GH deficiency should be offered the opportunity to continue rhGH therapy (0.2–0.5mg/day). Studies have demonstrated that rhGH replacement in adulthood may maintain lean body mass, muscle strength, and bone min-eral density. In addition, improved quality of life has been reported with treatment.

Cranial irradiation and GH deficiency

Cranial radiotherapy used in the treatment of tumours (intracranial, face, and nasopharynx) may cause GH deficiency. The GH axis is the most sensitive to radiotherapy, followed by the gonadal and adrenal axes, and finally the thyroid axis, which is least sensitive. There is a good corre-lation between radiotherapy dose and the occurrence of hypothalamic– pituitary dysfunction (Table 13.2). Risk of dysfunction is also related to dose fractionation (single is more toxic than divided), and age (younger more sensitive).

Pyschosocial deprivation

Children subjected to physical or emotional abuse may exhibit growth failure. This may be due to a reversible inhibition of GH secretion that improves within 3–4wks of being removed from the adverse environment. Catch-up growth is usually dramatic.

GH insensitivity syndrome

Moderate to severe short stature may be due to GH resistance. This may be due to a defect in the GH receptor or to a defect in post-receptor GH signalling.

Complete GH insensitivity syndrome (GHIS) results in severe short stature. It may be inherited as an autosomal recessive trait (Laron syn-drome). Affected individuals have high GH levels and low circulating IGF- I levels. Exogenous rhGH administration fails to increase IGF-I levels further (IGF-I generation test).