Popular weight loss and diabetes medicines including Mounjaro, Ozempic and Wegovy may carry a heightened risk of hair loss, researchers have found.
Patients taking GLP-1 agonist drugs have previously reported hair loss to regulators, but a new study involving around 50,000 people offers stronger evidence of an association.
Researchers examined electronic patient records from the University of Pennsylvania Health System, comparing rates of alopecia among adults using GLP-1 medicines to control diabetes with rates among patients taking other treatments.
The team said US regulators had already been alerted to possible hair loss linked to the drugs, particularly semaglutide, sold as Wegovy and Ozempic, and tirzepatide, marketed as Mounjaro.
The regulator has also received 148 reports of hair loss associated with semaglutide, compared with 164 reports last year.
For the latest research, investigators studied people with type 2 diabetes who were taking GLP-1 receptor agonists or alternative diabetes medicines known as SGLT-2 inhibitors and DPP-4 inhibitors.
Overall, 12,004 patients taking GLP-1s were compared with 15,221 SGLT-2 inhibitor users, while a separate comparison involved 11,964 GLP-1 users and 11,233 people taking DPP-4 inhibitors.
After accounting for factors that could affect the findings, including age and weight, the researchers found GLP-1 use was associated with a 37% greater risk of alopecia than treatment with SGLT-2 inhibitors.
Compared with DPP-4 inhibitors, GLP-1 medicines were linked to a 68% higher risk of hair loss.
Additional analysis indicated that the association involved non-scarring alopecia, a form of hair loss in which follicles remain intact and regrowth may still be possible.
Writing in the British Medical Journal, researchers including experts from the University of Pennsylvania in the US said: “Reports involving individual patients, together with analyses of the US Food and Drug Administration’s Adverse Event Reporting System, have documented hair loss after patients began using a GLP-1 receptor agonist, especially semaglutide and tirzepatide.
“The FDA has subsequently said it is assessing this possible safety signal.
“While hair loss does not usually cause physical injury, it can have profound psychosocial effects, undermining self-esteem and quality of life while making patients less likely to continue treatment.”
Exploring why the medicines might trigger hair loss, the researchers said the “most likely mechanism” involved weight loss and “reduced caloric intake”, although they stressed that further investigation was required.
Calorie restriction, they said, may “create physiological stress and lead to micronutrient deficiencies, including iron, zinc and biotin, potentially interrupting the normal hair growth cycle”.
The drugs’ “metabolic, hormonal, and immunological effects” could also play a role by influencing the growth and cycling of hair follicles.
GLP-1 receptor agonists, for instance, have been associated with changes in thyroid function, while delayed gastric emptying could affect the absorption of oral medicines, including thyroid hormone and sex hormone therapies, the researchers said.
“These shifts could affect hair growth through endocrine pathways, particularly among people who already have underlying hormonal conditions.”
The team concluded: “Our results build on earlier anecdotal safety signals, offering more systematic evidence that can strengthen clinical awareness of this potential adverse effect.”
