Muscle Dysfunction and Bone Loss in a Woman With Cystic Fibrosis and Obesity Treated With Glucagon-Like Peptide 1 Agonist: A Case Report.

Cystic fibrosis (CF) modulator therapies can lead to rapid and excessive weight gain. Obesity in CF can lead to undesirable metabolic complications including type 2 diabetes. Therefore, glucagon-like peptide 1 (GLP-1) agonists which can facilitate weight loss and improve metabolic profiles are increasingly prescribed to people with CF. We present the first case report documenting serial changes in body composition and bone mineral density over a 3-year period in an adult with CF, obesity and diabetes treated with Semaglutide and Elexacaftor/Tezacaftor/Ivacaftor (ETI). Our case experienced substantial weight gain following ETI initiation which exacerbated hyperglycaemia. This prompted initiation of Semaglutide, which over 12 months led to 14.8% total body weight loss and significant glycaemic improvement. However, serial assessments revealed declines in absolute muscle mass, muscle strength and bone mineral density despite prescription of tailored exercise and nutritional interventions. Our findings highlight the need for cautious use of GLP-1 in people with CF.