Linear growth in patients with hypophosphatemic vitamin D-resistant rickets: Influence of treatment regimen and parental height Sonia Balsan, MD, and Martin Tieder, MD From the Laboratoire des TissueCaIcifi6s, University R. Descartes, Paris, France, and the Pediatric Nephrology Unit, "'Assaf Harafeh" Medical Center, Sackler School of Medicine, Tel-Aviv, Israel The effects of different treatment regimens and the influence of parental height on the statural growth of 40 patients with hereditary vitamin D-resistant hyp o p h o s p h ~ t e m i c rickets were investigated. Three treatment regimens, e a c h with oral phosphate, were used: vitamin D (0.5 to 2 mg/day), c a l c i d i o l (50 to 200 ~tg/day), and la-hydroxyvitamin D3 (I to 3/~g/day). Mean duration of follow-up was 9.5 _+ 5.1 years. The results show that (1) there was no a c c e l e r a t i o n of growth before puberty for the majority of children treated with vitamin D (12/16) or calcidiol (13/15), whereas la-hydroxyvitamin 03 p r o m o t e d catch-up growth in 10 of 16 patients; (2) height gain during puberty was normal, irrespective of the treatment; (3) most vitamin D-treated male and female subjects and calcidioltreated male subjects had short adult stature, but the majority (75%) of the lahydroxyvitamin Da-treated groups had normal stature; (4) parental stature had little influence on the adult height of male subjects, but that of a f f e c t e d girls was positively correlated (p 0.3 and hypercalcemia (serum calcium level >2.65 mmol/L [10.6 mg/dl]). Follow-up study. The patients were regularly followed once a month for the first 3 months and then every 2 to 3 months. Biochemical tests, using standard laboratory techniques, included measurements of fasting serum total calcium, phosphorus, alkaline phosphatase activity, creatinine, and magnesium. Urinary calcium, phosphorus, and creatinine excretions were assessed on 24-hour urine samples, 2hour morning urine samples, or both. After 1980, annual or twice-yearly measurements of plasma immunoreactive parathyroid hormone were performed (Prof. C. Sachs, Department of Physiology, University Paris V) with, first, a C-terminal antiserum and then a mid-region antiserum and a modification of the method of Arnaud et al. 22 The circulating concentrations of 25-OHD and 1,25-(OH)2D of some patients were also monitored before and during treatment, by means of previously described techniques. 23, 24 The evo-

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lution of the patients' skeletal lesions was evaluated on radiograms of the legs and of the left hand and wrist, first after 3 months of therapy and then every 1 to 3 years. Height was measured with a stadiometer at least twice a year. Height and height-increase velocity were expressed in standard deviation scores, according to the data established for normal French children. 25 Final mature height was defined as the height attained after the pubertal spurt, with yearly statural increments not exceeding 1 cm for 2 successive years. In addition, the effects of a treatment regimen on final attainable growth for those patients who did not achieve final height was evaluated from the "predicted adult height." This measurement was calculated from the table for predicting adult height from skeletal age (revised for use with the Greulich-Pyle26 hand standard and thepercentage of mature height of the Berkeley study by Bayley and Pinneau27). The predicted height was calculated only for children older than 10 years of age and on an average of nine chronologic heights (range 6 to 13) per subject. Finally, to integrate the patients' inherited potential into the analysis of their height, we compared each patient's final or predicted height SDS with their raid-parental height SDS. 2s Statistical analysis. Grouped data were analyzed with the Student test; linear regressions were calculated by the least squares method. RESULTS Biochemical data. In all treatment groups, fasting serum phosphorus concentrations were maintained near l mmol/ L (3.[ mg/dl). However, the serum phosphorus concentration was checked to ensure that it was transiently normalized (1.3 to 1.5 retool/L; 3.9 to 4.5 mg/d[) 1 to 2 hours after oral phosphate supplementation. In one child, severe symptoms of gastric intolerance rapidly led to permanent withdrawal of phosphate supplements.Plasma iPTH values increased in five others; plasma iPTH became normal in all but one of these after interruption of phosphate supplementation, followed by administration of lower doses. The single patient with secondary hyperparathyroidism (plasma iPTH 140 pg/ml vs