Growth hormone therapy in hypophosphatemic rickets
Article Abstract:
Familial hypophosphatemic rickets (FHPR) is a disorder characterized by abnormal phosphate transport in the kidney, persistent hypophosphatemia (low levels of phosphate in the blood), rickets (a disease of bone mineralization), and short stature. It is usually treated by high doses of phosphate and calcitriol (the active form of vitamin D, important in bone mineralization), but some evidence suggests that administering growth hormone could also be helpful. This was evaluated in a group of 11 children and adolescents (all with short stature) with FHPR who participated in a 10-week study during which they received, in sequence, no treatment, growth hormone only, and growth hormone plus phosphate and calcitriol. The nine youngest subjects continued to take growth hormone and conventional therapy (oral calcitriol and phosphate) for another six months after the study ended. Subjects' levels of growth hormone, phosphate, calcium, and other substances were monitored at regular intervals. During the growth hormone-treatment phase, subjects' blood phosphate levels increased to levels similar to those resulting from conventional therapy. The levels of alkaline phosphatase (an enzyme involved in bone remodeling) and osteocalcin, a protein whose concentrations probably reflect bone formation, also increased with growth hormone treatment. The subjects who took all three substances for six months had increased growth rate scores. Overall, the results suggest that growth hormone affects blood phosphate concentrations in a positive way. This could be of therapeutic benefit for people with FHPR; more investigations are needed to evaluate this possibility. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Diseases of Children
Subject: Health
ISSN: 0002-922X
Year: 1991
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X-linked hypophosphatemia: genetic and clinical correlates
Article Abstract:
X-linked hypophosphatemia is a genetic disorder characterized by a defects in the mechanism that reabsorbs phosphate back into the kidney tubule and the kidney enzyme 1-alpha-hydroxylase, which normally converts 25-hydroxycalciferol to 1,25-dihydroxycalciferol. The gene for this disorder is carried by the X chromosome, a thread-like structure in the cell nucleus that determines female sex characteristics. X-linked hypophosphatemia results in abnormally low blood levels of phosphate, growth delay and defects in bone shape and structure due to impaired bone formation. This genetic disorder is treated with phosphate supplements to restore blood phosphate levels. Specifically, 1,25-dihydroxyvitamin D3 is given to restore levels of 1,25 dihydroxycalciferol and diuretics are given to increase elimination of fluids and calcium and reabsorption of phosphate. Diuretics prevent or reduce the side effects of treatment with 1,25-dihydroxyvitamin D3, which include elevated blood and urine levels of calcium. Unlike other forms of hypophosphatemia, X-linked hypophosphatemia is not associated with muscle weakness. However, lower than normal levels of inorganic phosphate have been detected in the muscle cells of patients with X-linked hypophosphatemia. Recent studies using the Hyp mouse, the animal model for X-linked hypophosphatemia, suggest that a hormonal factor may be responsible for the development of this disorder. Advances in genetic studies of X-linked hypophosphatemia include the identification and localization of two genes, Hyp and Gy. Future areas of research in X-linked hypophosphatemia are presented. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Diseases of Children
Subject: Health
ISSN: 0002-922X
Year: 1991
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Standardized percentile curves of body-mass index for children and adolescents
Article Abstract:
Obesity has significant medical and psychological repercussions for children and teenagers. This problem is most accurately determined in adults by measuring body density or by other techniques that are generally impractical and not well standardized for children. Adiposity, the amount of fat tissue, can also be measured using indirect techniques such as skinfold thickness determination, but this can be affected by improper technique and variability in distribution of subcutaneous (under the skin) fat. Body-mass index (BMI), or Quetelet Index, another indirect technique, is calculated by the weight divided by height squared and is easily determined in children. The index has been useful as an assessment of obesity, and in children, has been predictive of later obesity. BMI is influenced by age, sex, and race, and standards for BMI have been developed for female and male white children, aged 1 to 19, using data for 5,679 children from the First National Health and Nutrition Examination Survey. The percentile distribution of females and males varies considerably at some ages, especially after age 14. The standardized curves from this study should be useful in monitoring the development of obesity and effects of treatment. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Diseases of Children
Subject: Health
ISSN: 0002-922X
Year: 1991
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