Study: Patients With Hypothyroidism Who Lost Weight on Semaglutide Saw Decreases in TSH Levels

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Patients with a history of hypothyroidism who were prescribed a glucagon-like peptide (GLP)-1 medication and lost more than 5 pounds saw a reduction in their thyroid-stimulating hormone (TSH) levels, according to the authors of a study conducted by Epic Research.¹ Additionally, those who gained weight had no statistically significant change in their TSH levels.¹ Prior research has shown conflicting results on GLP-1 medications and thyroid function; however, medications can affect metabolic pathways, therefore altering thyroid hormone production.²

The association of thyroid hormones and weight loss were determined in a 2014 study published in Thyroid.³ The findings demonstrated that moderate dietary restriction in 47 participants with a body mass index of 25 to 45 kg/m² resulted in a 6.3 ± 0.9 kg (6.5 ± 1.0%) weight loss. At baseline, TSH levels and T3 concentrations were significantly associated with fat mass, and after weight loss, T3 decreased significantly (from 112.7 ± 3.1 to 101.8 ± 2.6 ng/dL, P < .001) in the absence of significant changes in TSH or free T4. Additionally, the T3 to free T4 ratio decreased significantly in those who lost more than 5% of their body weight.³

Knowing the associations between the thyroid and weight loss, the investigators of this study aimed to further understand the relationships between GLP-1 medications, weight change, and TSH levels and enrolled 21,538 patients with hypothyroidism for their investigation.^1,2 Patients were prescribed semaglutide (Ozempic, Weygovy; Novo Nordisk), dulaglutide (Trulicity; Eli Lilly and Co), liraglutide (Victoza; Novo Nordisk), or exenatide (Byetta; Eli Lilly and Co) and were stratified by their weight change after starting their medication. The amount of weight change was calculated using the patient’s weight at the time of GLP-1 medication initiation and their weight when a follow-up TSH level was taken.¹

According to the study findings, patients who were prescribed semaglutide and lost over 5 pounds saw the greatest reduction of their TSH levels (-0.55 mU/L). Within this subgroup, exenatide demonstrated the smallest reduction in TSH (-0.36 mU/L). Semaglutide had different effects in the “lost 0 to 5 pound” group and weight gain group, demonstrating TSH changes of -0.27 mU/L and 0.04, respectively. Additionally, exenatide was the only GLP-1 medication that resulted in a decrease in TSH levels (-0.05 mU/L) in the weight gain group, but the investigators noted that this group saw no statistically significant changes in their levels.¹

Because thyroid dysfunction can often occur with metabolic conditions, such as diabetes and obesity, investigators of a June 2024 review published in Biomolecules aimed to find a deeper understanding of GLP-1 medications’ interactions with thyroid dysfunction. Additionally, they intended to clarify the safety of GLP-1 medications in patients who have both diabetes and thyroid disorders.²

These authors determined that although multiple studies have explored these associations, the current evidence is inconclusive because of conflicting results. However, an interaction between thyroid dysfunction and metabolic conditions was confirmed. Additionally, they suggested that because—as of the study’s publication—there are no guidelines to provide definitive directions, thyroid function tests in routine screening of patients with diabetes should be performed, particularly on those who are being treated with GLP-1 medications.²

With these data, additional research will be needed to confirm findings.^1,2 The authors of the review in Biomolecules suggest that larger sample sizes and longer-term studies may help gather clearer results.²

REFERENCES

1. Epic Research. Patients Who Lose Weight After Starting GLP-1s More Likely to See Thyroid Level Improvement. News release. November 19, 2024. Accessed November 22, 2024. https://www.epicresearch.org/articles/patients-who-lose-weight-after-starting-glp-1s-more-likely-to-see-thyroid-level-improvement

2. Capuccio S, Scilletta S, La Rocca F, et al. Implications of GLP-1 Receptor Agonist on Thyroid Function: A Literature Review of Its Effects on Thyroid Volume, Risk of Cancer, Functionality and TSH Levels. Biomolecules. 2024; 14(6):687. doi:10.3390/biom14060687

3. Agnihothri RV, Courville AB, Linderman JD, et al. Moderate weight loss is sufficient to affect thyroid hormone homeostasis and inhibit its peripheral conversion. Thyroid. 2014;24(1):19-26. doi:10.1089/thy.2013.0055