Cystic fibrosis (CF) is a catabolic condition, and children affected with this disease frequently have problems with growth, despite adequate nutrition. We hypothesize that the anabolic effects of growth hormone (GH) will improve the height and weight of CF patients and thereby improve their clinical status and their quality of life. We further hypothesize that these effects will be sustained for at least one year after GH treatment is complete.

We will test our hypotheses by recruiting 40 CF children from five CF centers (8 per center) across the country. Patients will be randomly assigned to receive treatment with GH (0.3 mg/kg/wk) during the first 12 months, or during the second 12 months. All subjects will be followed every three months for the entire 24 months. Growth data and PFT data from the year prior to study will be obtained from the medical record for each subject. Our specific aims include:

1. To determine the effect of GH on height, height velocity, body weight and lean body mass. We will measure height and weight using a standardized stadiometer and scale, respectively, every three months during the study. From these measurements we will calculate height and weight velocity and height and weight Z score. Lean body mass (LBM) will be measured by DEXA every six months. Baseline height and weight will be analyzed as covariates to determine whether children whose height and/or weight are at the lowest percentiles achieve greater improvement in height and weight velocity and lean body mass. This specific aim tests the hypothesis that GH significantly improves height, height velocity, weight, weight velocity and lean body mass in CF children irrespective of growth prior to starting the drug.
2. To determine the effect of GH on pulmonary function. Pulmonary function tests, including FEV1, FVC and PImax and PEmax (for estimation of respiratory muscle strength), will be measured at baseline and every 6 months in all subjects. We will document inpatient admissions and outpatient antibiotic therapy during the study. Baseline pulmonary function will be analyzed as a covariate to determine whether children with good pulmonary function achieve greater benefit than children with poor pulmonary function. This specific aim tests the hypothesis that GH use improves pulmonary function in CF children regardless of level of pulmonary functions prior to using the drug.
3. To determine if GH use in CF patients positively impacts quality of life. At baseline and every six months, we will administer a 15 minute questionnaire to both the parent and patient to assess quality of life. These questionnaires entitled "The Cystic Fibrosis Questionnaire" have been recently developed and tested for quality. They are specific for CF patients and have been approved by the National CF Foundation. This specific aim will test the hypothesis that GH use improves quality of life in CF patients.
4. To determine if the clinical improvement obtained from GH use is sustained. Those patients treated with GH during the first 12 months will be followed for 12 months after treatment to determine if the outcome variables remain better than baseline after growth hormone therapy is discontinued. This specific aim tests the hypothesis that GH use results in sustained improvement in height velocity, weight velocity, lean body mass, pulmonary function and quality of life.

Inclusion Criteria:

• prepubertal CF patients (ages 5-12)
• capable of performing pulmonary function tests
• less than the 25th percentile for age and sex normal values for height and/or weight.

Exclusion Criteria:

• previous diagnosis with diabetes
• previous insulin requirement
• inability to perform pulmonary function testing
• colonization with burkholderia cepacia