The effect of growth hormone treatment on biochemical indices in hypophosphatemic rickets

Background. Growth hormone (GH) in combination with conventional therapy in hypophosphatemic rickets (HR) has been shown to promote renal phosphate (P ) conservation and to result in a better metabolic control. This study aime d at investigating the acute biochemical effects of GH in 7 patients (5 fem ale, 2 male) with HR aged between 2.16 and 16 years. Methods: Each patient received the following in a sequential design: oral P plus 1,25-dihydroxyvi tamin D-3 [1,25-(OH)(2)D-3] therapy to determine the optimum doses for base line requirement followed by GH-only therapy and GH +1,25-(OH)(2)D-3 therap y and GH + P + 1,25-(OH)(2)D-3 therapy each for 2 weeks with 1 washout week off treatment in between. GH was given at a dose of 0.03 mg/kg/day s.c. on a daily basis. The dose of oral P used ranged between 500 and 2,000 mg/day , and the dose of 1,25-(OH)(2)D-3 ranged between 0.25 and 0.5 mug/day and w as kept constant for each child throughout the study. Results: Laboratory i nvestigations repeated at the end of each treatment, and the first washout period showed that the serum P level was highest (2.9 ng/ml) during the GH + P + 1,25-(OH)(2)D-3 period with higher serum 1,25-(OH)(2)D-3 levels: 50.9 +/- (SD) 23.4 ng/l. Parathyroid hormone and alkaline phosphatase levels di d not show a significant difference between the periods. The tubular P reab sorbtion rate showed an insignificant increase during GH therapy periods. C onclusion: Considering the fixed dose of P and calcitriol, it may be conclu ded that GH added to conventional treatment in HR resulted in a slight impr ovement in the biochemical parameters without any side effects at the short term. Copyright (C) 2001 S. Karger AG, Basel.