GROWTH-HORMONE SECRETION AND SERUM INSULIN-LIKE GROWTH-FACTOR-I CONCENTRATION IN X-LINKED HYPOPHOSPHATEMIC RICKETS BEFORE AND AFTER TREATMENT

The aetiology of growth retardation In children with X-linked hypophos phatemic rickets (HPR) has not been totally defined. We evaluated grow th hormone (GH)/insulin-like growth factor-I (IGF-I) changes in relati on to linear growth and biochemical parameters in seven children with X-linked hypophosphatemic rickets before and after treatment with 1,25 -dihydroxyvitaminD3 and phosphate therapy for a year or more. Moreover , we compared patients' growth data and GH/IGF-I changes with those fo r 20 age-matched children with normal variant short stature (NVSS) [wi th normal GH secretion and height standard deviation score (HtSDS) bef ore -2]. Before treatment, all children with HPR secreted normal GH in response to clonidine provocation (>10 mu g/l) and their IGF-I concen tration was significantly lower than those with NVSS. The HtSDS and gr owth velocity (GV) of children with HPR improved significantly after ( -3.05, 8.9 cm/year, respectively) v. before (-3.9 and 4.1 cm/year, res pectively) therapy. Their serum IGF-I concentration increased signific antly from 76.7 ng/ml before to 99.6 ng/ml after treatment. In summary children with HPR had no abnormality of GH secretion but improvement of their linear growth was associated with significant increase of cir culating IGF-I concentration after treatment.