PSHP 2026 Residency Conference

Purpose:
To determine whether initiating a glucagon-like peptide (GLP) receptor agonist (GLP)in adults with hypothyroidism on a stable levothyroxine regimen leads to a change in levothyroxine requirements.


Methods:
A retrospective study was conducted by chart review using electronic health records at Penn Medicine Lancaster General Health from July 2020 to June 2024. Patients were included if they were at least 18 years of age, diagnosed with hypothyroidism, on a stable dose of levothyroxine prior to initiation of a glucagon-like peptide receptor agonist continued for at least 6 consecutive months, and at least 1 thyroid-stimulating hormone level within 6 months before and after a glucagon-like peptide receptor agonist. The primary endpoint is change in levothyroxine dose at 6 months after initiation of a glucagon-like peptide receptor agonist. Secondary endpoints include percentage weight loss at 6 months, change in thyroid-stimulating hormone at 6 months, change in levothyroxine dose at 12 months, and percentage of weight loss compared to percentage change in levothyroxine at 6 months.


Results:
Among 136 patients, 18 (13.2%) had a levothyroxine dose change within 6 months of glucagon-like-peptide receptor agonist initiation. Firth logistic regression found no significant associations between dose change and glucagon-like-peptide receptor agonist type, age, sex, smoking status, or weight change (all p>0.05). Secondary analysis showed patients with levothyroxine dose changes had greater reductions in thyroid-stimulating hormone at 6 months versus those without changes (median -1.69 vs 0.00 mIU/L; p=0.015). At 12 months, weight change did not differ between groups requiring levothyroxine adjustment and those without adjustment (p=0.790).


Conclusion:
Glucagon-like-peptide receptor agonist initiation was not associated with predictable changes in levothyroxine requirements based on baseline patient factors or weight loss. However, greater reductions in thyroid-stimulating hormone were associated with levothyroxine dose adjustments, suggesting thyroid function should be monitored after glucagon-like-peptide receptor agonist initiation. Larger studies are needed to confirm these findings.


IRB APPROVAL:
PENN IRB Protocol #: 859751; approved 11/16/2025