2026 Eastern States Conference

Title: 
Changes in thyroid stimulating hormone levels and levothyroxine dosage for patients prescribed with injectable weight loss medications

Authors: 
Sammie Zou, Pharm D; Gabriela Smicherko, Pharm D; Holland Hood, Pharm D
Wilkes-Barre Veterans Affairs Medical Center, Wilkes-Barre, PA

Learning Objective:
By the end of this presentation, participants will be able to evaluate the importance of monitoring thyroid stimulating hormone (TSH) levels and address potential need for levothyroxine dose adjustment for patients prescribed with injectable weight loss medications.

Objective: 
The objective of this study is to monitor change in weight and TSH levels to assess the need for dose adjustment of levothyroxine in patients taking injectable weight loss medications.

Self Assessment Question:
True or False: TSH monitoring may be beneficial in patients taking both levothyroxine and injectable weight loss medication.

Methods:
In this retrospective chart-review, quality-improvement project data was obtained from the Computerized Patient Record System (CPRS) for patients with obesity and receiving injectable weight loss medication (semaglutide or tirzepatide) along with receiving levothyroxine for hypothyroidism from September 2022 to September 2025. Patients excluded were those with a history of thyroid cancer, receiving amiodarone, unable to tolerate injectable weight loss medications, utilizing injectable weight loss medication with only minimal weight loss effect (less than five percent reduction in body weight), or had no baseline TSH levels within at least six months while receiving levothyroxine. The primary outcome was the change in dose of levothyroxine since the initiation of an injectable weight loss medication, and the secondary outcomes were changes in weight and changes in TSH levels at baseline, three months, six months, and years one through three.
 
Results: 
A total of 170 charts were reviewed, and 57 patients met inclusion criteria and were included in the analysis. The primary outcome showed that 71.9% of patients had no changes made in their levothyroxine dose, 24.6% of patients had a decrease in levothyroxine dose, and 3.5% of patients had an increase in levothyroxine dose. Patients with a higher degree of weight loss did experience a reduction in their levothyroxine dose, and the average TSH levels have decreased with initiation of a weight loss injectable before stabilizing after dose adjustments of levothyroxine were made.

Conclusion: 
Most patients did not have levothyroxine dose adjustments following initiation of weight loss injectable. However, patients with greater weight loss had a greater likelihood of needing a dose reduction with their levothyroxine. Data was also limited due to lack of a recent TSH level for some patients which emphasized the need for routine monitoring of TSH levels particularly every 6 months and every 3 months for patients experiencing at least 15% weight loss until weight loss stabilizes.