Inclusion Criteria:  • Patients diagnosed with gastroesophageal reflux or gastroesophageal reflux disease aged 16 to18 years.  Exclusion Criteria:  Patients with a malabsorptive disease. Patients with any chronic disease. Patients who use any medication that may affect calcium and bone metabolism. Patients who used proton pumps inhibitor within the last 3 months. Patients who do not use lansoprazole in the study group. Patients whose blood and urine samples are not taken in the eighth week of treatment.