(1) Objectives: Our aim in this study was to investigate the effects of growth hormone on physical growth and clinical status of children with cystic fibrosis. (2) Design: This study is a before-after clinical trial which study population are 20 patients with cystic fibrosis diagnosed based on clinical evidence (steatorrhea, nasal polyp, rectum prolapse, history of ileus meconium and relapsing pneumonia), laboratory findings (sweat test more than 60 meq/dl) and genetic evaluation (mutation in CFTR gene) and referred to liver and gastrointestinal wards and clinics. These children will be included in the study after qualifying the inclusion and
exclusion criteria and obtaining the informed consent. (3) Setting and conduct: After measuring height, weight, body mass index and primary physical exam and filling checklists, blood sample will be taken to measure blood cells, blood glucose and electrolytes, creatinine, liver function tests and albumin. In first 6 months, without administrating growth hormone, growth rate, times of lung infections, times of intravenous antibiotic therapy and hospitalization will be measured every two months. After 6 months laboratory exams will be repeated and height and weight will be recorded and spirometry will be performed for all the patients. Growth hormone will be administered with dose of 35 mg/kg/week and will be injected subcutaneous every day. Growth rate and clinical status will be recorded every 2 months for six months. At the end of second six months laboratory exams and spirometry will be performed again. Inclusion criteria are age under 12 years old and height and weight less than third percentile for age and gender. Exclusion criteria are having diabetes, cirrhosis of the liver and hypoalbuminemia and oxygen-related lung disorders. (4) Interventions: Patients will be treated with growth hormone for six months with dose of 35 mg/kg/week and will be injected subcutaneous every day. (5) Main outcome measure: Height, weight, body mass index, times of hospitalizations, times of intravenous antibiotic therapy which will be recorded every two months after initiating treatment with growth hormone and will be continued for six months.