Losing weight, but not hair. One of the latest side effects attributed to the new generation of drugs to combat obesity is alopecia. The FDA (U.S. drug agency) is reviewing a series of reports to assess if hair loss is directly related to the intake of some GLP-1 receptor agonists approved for type 2 diabetes and obesity.
Among them are semaglutide, marketed as Ozempic, Rybelsus, and Wegovy; liraglutide, marketed as Saxenda and Victoza; and tirzepatide, marketed as Mounjaro and Zepbound.
The FDA has noted hair-related events among the adverse events reported by patients during trials. There are over 400 reports of patients who took semaglutide or tirzepatide mentioning alopecia.
A review by this agency prior to the approval of Wegovy pointed out that hair loss and weakening were among the most common issues among participants who received semaglutide in Novo Nordisk's clinical trial, compared to those who received a placebo.
In an article published in The New England Journal of Medicine in 2021, doctors also noted the number of patients reporting alopecia in tirzepatide trials for obesity by Eli Lilly.
In a recent systematic review published in Nature Medicine, hair loss is not mentioned among the 175 positive and negative effects these drugs have on the body. This work was based on the analysis of data from 2.4 million participants.
Goodbye to Hair: GLP-1s Are Not the Direct Culprits
To the relief of many, there is no direct link between taking the drug and hair loss. Experts believe that hair loss with these drugs may be due to a medical condition known as telogen effluvium, and it may not be a direct effect of the medication itself, although further research is needed.
In this regard, Cristóbal Morales, spokesperson for the Spanish Society for the Study of Obesity (Seedo), explains that "hair loss is taken into account when prescribing these medications." Therefore, the therapeutic positioning report by the Spanish Agency of Medicines and Medical Devices (Aemps) on tirzepatide mentions it as an effect to monitor. "When there are abrupt weight losses, it is usually common," Morales points out.
In fact, hair loss is more common after bariatric surgery: one in three patients undergoing surgery to treat obesity will experience this issue, which will improve over time. This affects more women than men, as reported in a 2021 analysis in Obesity Surgery. This situation is associated with low levels of zinc, folic acid, and ferritin.
The American Hair Loss Association (AHLA) has highlighted this circumstance. Spencer David Kobren, its founder and president, suggests in an article published in Dermatology Times, the hypothesis that hormonal changes caused by semaglutide and similar drugs may trigger not only temporary telogen effluvium, but also early onset of male and female pattern hair loss, also known as androgenetic alopecia.
It is important to distinguish between telogen effluvium, which occurs due to the disruption of the normal hair growth cycle, and androgenetic alopecia, which is a progressive condition that can worsen over time and lead to permanent hair loss.
Obesity experts also consider hair loss due to hormonal changes that occur when significant weight loss happens rapidly. The good news is that this effect is temporary: it usually starts after the first few kilos are lost and stops between six months and a year after reaching the appropriate weight stabilization.
AHLA urges users to consult a doctor, as they emphasize the off-label use beyond diabetes and obesity, and without medical supervision justifying the use of GLP-1 at appropriate doses. Especially to determine the cause of hair loss, as rapid weight loss is often accompanied by nutritional deficiencies that lead to hair loss. Therefore, endocrinologists, as Morales explains, "determine the necessary doses of the drugs at each moment, conduct tests on patients to monitor deficiencies, and design nutritional plans to prevent them."