Synthetic human growth hormone for treating X-linked hypophosphatemia (or Vitamin D resistant rickets) in children

Standard treatment of X-linked hypophosphatemia can heal rickets but does not always raise the level of phosphates in the blood or return growth levels to normal. It is unclear whether combining human growth hormone therapy with standard treatment improves the phosphate levels, growth rates and bone mineral density. Only one small trial with five children was included in this review. The human growth hormone treatment improved the z score for height and briefly increased the level of phosphates in the blood. However, we found no conclusive evidence that favours the use of human growth hormone treatment for this condition. There have not been enough trials of human growth hormone treatment for this condition and more research is needed.

Authors' conclusions: 

We have found no conclusive evidence to indicate that the use of recombinant human growth hormone therapy in children with X-linked hypophosphatemia is associated with changes in longitudinal growth, mineral metabolism, endocrine, renal function, bone mineral density, and body proportions.

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Background: 

Conventional treatment of X-linked hypophosphatemia with oral phosphate and calcitriol can heal rickets, but it does not always raise serum phosphate concentrations significantly, nor does it always normalize linear growth. Some clinical trials suggest that combining recombinant human growth hormone therapy with conventional treatment improves growth velocity, phosphate retention, and bone mineral density, but some clinical trials suggest that it appears to aggravate the pre-existent disproportionate stature of such children.

Objectives: 

To determine whether recombinant human growth hormone therapy for children with X-linked hypophosphatemia is associated with changes in longitudinal growth, mineral metabolism, endocrine function, renal function, bone mineral density, body proportions, and also with any adverse effects.

Search strategy: 

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. In addition, we searched the Cochrane Central Register of Controlled Trials, Ovid MEDLINE and the reference lists of identified trials and other reviews. We also undertook some additional handsearching of relevant journals and conference proceedings.

Date of the most recent search of the Group's Trials Register: 17 March 2011.

Selection criteria: 

All randomized controlled trials or quasi-randomized controlled trials comparing growth hormone (alone or combined with conventional treatment) with either placebo or conventional treatment alone in children with X-linked hypophosphatemia.

Data collection and analysis: 

Two authors independently assessed trials for risk of bias and extracted data from eligible trials.

Main results: 

The searches identified six trials, of which one met the inclusion criteria, including a total of five participants. In this trial, rhGH therapy improved the height standard deviation score (z score), and transiently increased serum phosphate and tubular maximum for phosphate reabsorption.

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