Background: Cystic fibrosis (CF) affects about 30,000 persons in the United States. Patients with CF tend to be shorter and weigh less than persons without CF. This lower weight is associated with increased morbidity and mortality, and short stature is a risk factor for poor pulmonary function. Previous studies of recombinant human growth hormone in children with CF who had height and weight in the 10th percentile or lower for age showed improved growth and increases in lean body mass and protein turnover. However, this effect has not been studied in patients who are less severely affected by CF. Studies also have not evaluated the link between recombinant human growth hormone therapy and increased growth rate, clinical outcomes, and quality of life.
The Study: Sixty-one children seven to 12 years of age from CF centers in the United States, whose weight and height were in the 25th percentile or lower for age, were enrolled in this two-year study. For the first year, Hardin and colleagues randomized the participants into a treatment group using daily injections of recombinant human growth hormone (Nutropin AQ) or a no-treatment group. The groups were crossed over in the second year to ensure that each participant only received hormone injections for one year.
Height and weight were measured every three months, and lean body mass and bone mineral content were measured every six months. Patients and their parents completed CF quality-of-life questionnaires every six months. Hospitalizations, intravenous antibiotic courses, forced vital capacity, and forced expiratory volume in one second were recorded to assess clinical status.
Results: Patients in the treatment group who received injections during the first year showed an increase in height, weight, and bone mineral content. They also had significantly fewer hospitalizations compared with the no-treatment group. Improvements were similar in the no-treatment group when they crossed over to treatment in the second year. Two quality-of-life measures, perceived weight and a better body image, showed significant improvement; the other parameters were not significantly different. Despite daily injections, the patients receiving them did not report any increased treatment burden.
Conclusion: These findings suggest that increasing growth velocity improves pulmonary function, even after treatment has stopped, and it may reduce the predicted annual decline in CF patients. The authors suggest that the high cost of growth hormone injections could be offset by the reduction of one hospitalization a year.