Isolated growth hormone deficiency in children and adolescents.

Although it is difficult to reach international agreement on the definition of growth hormone deficiency (GHD) in children and adolescents, great efforts to do so have been made during the last two decades. A somewhat limited definition of GHD is: a combination of auxological, clinical, biochemical and metabolic abnormalities caused by lack or insufficiency of GH secretion that results in a decrease in the production of GH-dependent hormones and growth factors. Its aetiology is very complex. Therefore, specific studies must be performed during different periods of childhood (neonatal, prepubertal and pubertal periods). Auxological parameters, particularly growth velocity (GV), are still considered the best clinical measures for analysing human growth. The spectacular advances in our understanding of molecular biology during the past twenty years have allowed, and will continue to allow, a more and more precise diagnosis of the molecular anomalies of human growth. This will, in turn, allow changes caused by genetic lesions to be more efficiently distinguished from those due to nutritional, organic, tumoural, psychological or traumatic causes. Our knowledge of the molecular bases of undergrowth due to a deficiency in GH has developed as a result of the localisation and characterisation of human genes which code for proteins implicated in the hormonal regulation of growth. These genes include pituitary GH (GH1), pituitary transcription factor 1 (Pit-1), the prophet of Pit-1 (PROP-1), the pituitary transcription factor LHX3, the transcription factor HESX1 and the GH-releasing hormone receptor (GHRHr). In addition, magnetic resonance imaging is the best available imaging method for the evaluation of size and structure of the pituitary and the parasellar region.

Turner's syndrome.

Turner syndrome (TS) is the most common sex-chromosome abnormality in females. Short stature and hypogonadism are the classical clinical findings. The spontaneous final height (FH) ranges between 139 and 147 cm, representing a growth deficit of about 20 cm with respect to the unaffected population. GH therapy improves FH and should be started during childhood at a high dose of about 1 IU/kg/week (range 0.6-2 IU/kg/week). Some authors advocate combined therapy with an anabolic steroid at various doses (e.g. oxandrolone 0.05-0.1 mg/kg/day). This treatment results in a significantly increased FH, a large proportion of treated girls reaching a FH of more than 150 cm. Gonadal function is compromised during adolescence in about 80% of girls with TS, whilst in about 20% pubertal development occurs spontaneously. Oestrogen therapy should be started at the age of 13-14 years in hypogonadic patients; early onset of treatment (before 12 years) seems to compromise FH. Other concerns in these patients are fertility and osteopenia.