Long-term growth hormone treatment in children with renal hypophosphatemic rickets: Effects on growth, mineral metabolism, and bone density

Abstract

Objective: To evaluate the effects of treatment with recombinant human growth hormone (rhGH) on growth, mineral metabolism, and bone density in children with renal hypophosphatemic rickets (RHR). Design: Long-term rhGH treatment combined with conventional therapy with 1,25-dihydroxyvitamin D 3 plus inorganic phosphate salts. Setting: Endocrine unit, department of pediatrics, university hospital. Subjects: Twelve patients (5 boys; age range 4.6 to 12.5 years, median 7.0 years) were subdivided into two groups of six patients on the basis of the median of height z score (±2.41) and the median of bone age/statural age (BA/SA) ratio (1.23). Group A included patients with a severe degree of short stature (height z score ±3.4 ± 0.5) (mean ± SD) and altered BA/SA ratio (1.26 ± 0.08); group B included patients with a lesser degree of short stature (height z score ±2.1 ± 0.6, p <0.001 vs group A) and more normal BA/SA ratio (1.04 ± 0.15, p <0.01 vs group A). Intervention: Group A received rhGH treatment (0.6 IU/kg per week subcutaneously) combined with conventional therapy; group B received conventional therapy alone. Measurements: Height, growth velocity, predicted adult height, serum values of calcium, phosphate, bone alkaline phosphatase isoenzyme, osteocalcin, propeptides of type I and type III procollagen, intact parathyroid hormone, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and urinary calcium/urinary creatinine ratio and tubular maximum for phosphate reabsorption normalized to the glomerular filtration rate (TmP/GFR), as well as radial bone density, were measured at baseline and for 3 years. Results: Height z score, growth velocity z score, predicted adult height, serum values of phosphate, bone alkaline phosphatase isoenzyme, osteocalcin, propeptides of type I and type III procollagen, intact parathyroid hormone, 1,25-dihydroxyvitamin D, and TmP/GFR, as well as radial bone density, improved significantly only in group A. Serum calcium and 25-hydroxyvitamin D, and urinary calcium/urinary creatinine ratio did not change in either group. Conclusions: Long-term rhGH administration may benefit growth, phosphate retention, and bone density in patients with RHR, without evidence of side effects. (J P EDIATR 1995;127:395-402)