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

## TL;DR

A woman with cystic fibrosis, obesity, and diabetes experienced weight loss and improved blood sugar with a GLP-1 agonist, but also lost muscle and bone mass.

## Contribution

This is the first case report tracking body composition and bone changes in a CF patient treated with a GLP-1 agonist.

## Key findings

- Semaglutide led to 14.8% weight loss and improved glycemic control in a CF patient.
- Despite interventions, the patient experienced declines in muscle mass, strength, and bone mineral density.
- GLP-1 agonists may have unintended negative effects on muscle and bone in CF patients.

## Abstract

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.

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 body composition and BMD changes in an adult with CF, obesity and diabetes receiving Semaglutide and highlight concerning losses in bone mass and muscle function despite metabolic benefits.