GLP1 receptor agonists and hair loss

“Doc, my hair is falling out. Am I going bald?” 

Sylvie’s in for a review of her tirzepatide having started it for type 2 diabetes three months ago. The drop in HbA1c has been impressive, as has her weight loss. She pushed through the GI side effects, but her hair has her troubled. Every day she brushes it and much more than usual seems to come out. What’s going on?

Perhaps a paper published in the BMJ this summer has the answer.

Titled “risk of hair loss associated with glucagon-like peptide-1 receptor agonists in adults with type 2 diabetes” I was excited (don’t judge me) to know more about this area because hair loss is such a commonly raised issue with patients in general practice, increasingly so in the new world of weight loss drugs.

The paper used electronic health record data from an American university hospital to conduct a trial emulation – a technique to allow researchers to mimic a randomised controlled trial using observational data. 

The researchers looked for rates of alopecia in adult patients with type 2 diabetes following initiation of either GLP1ra and compared this against patients initiating SGLT2i or DPP4 inhibitors.

The results showed that, overall, the risk of alopecia was increased with the use of GLP1ra compared to SLGTis and DDP4is, but not by much. Generally, the risk was low: around 3% over 5 years with GLP1ras versus around 2% for the others. 

An important question here is: what do the authors mean by ‘alopecia’? While most of us would consider this to mean the condition alopecia areata, in the broadest medical sense it simply means hair loss. The researchers examined the subtypes of alopecia and found that rates of non-areata, non-scarring alopecia were 15 times higher than alopecia areata itself.

While the paper doesn’t give us the figures, in reality, most of these cases of non-scarring alopecia will be telogen effluvium. 

Not heard of this before? You will recognise the condition if not the name: this is diffuse hair loss which can occur after acute events or stressors (e.g. severe illness, thyroid disease, pregnancy, malnutrition, iron deficiency anaemia or vitamin D deficiency) but we commonly see after marked weight loss. 

As explained by the British Association of Dermatologists, humans normally lose between 30 and 150 hairs each day from the scalp. At any one time around 15% of hair follicles are in a shedding phase, but this at least doubles with telogen effluvium. This will often be very noticeable as more hair may be found after washing or brushing the hair than normal. It often occurs rapidly in response to a stressor and may last for 3-6 months after the stressor has ended. The good news for patients is that the effects are completely reversible as long as the underlying driver is addressed.

The diffuse nature of telogen effluvium differentiates it from other common causes of alopecia including the typically patchy alopecia areata or patterned hair loss seen with androgenetic (‘male pattern’) alopecia. (JAMA has a nice, concise review.)

GLP1ras may not directly cause telogen effluvium (although a direct effect has not currently been excluded) but the associated significant or rapid weight loss is the likely driver. After bariatric surgery between 30-60% report hair loss, more so with the substantial weight loss seen after gastric bypass surgery. 

It’s perhaps surprising that the BMJ paper did not report higher rates of hair loss with GLP1ras. Existing data suggests the rate to be between 3 and 5%, and one wonders if this could still be under-reported. The BMJ paper did not give information on the degree of weight loss in its participants, so it may be that most patients didn’t reach a critical velocity of weight loss or absolute reduction in body mass to trigger telogen effluvium. Weight loss from GLP1ras tends to be less marked in patients with T2DM than those without using it purely for weight loss. Its plausible to expect to see this issue more in the latter group and with use of more potent treatments such as tirzepatide.

How should we counsel Sylvie?

First, we need to clinically diagnose telogen effluvium, differentiating it from other forms of hair loss. An absence of other likely causes suggests her tirzepatide is the likely culprit. There are no other treatments that will help, so she doesn’t need to tear (more of) her hair out trying to find one, and neither do you. We can reassure her that this is a common consequence of the treatment and she won’t go bald, and that once her weight stabilises it is likely to resolve. No need to tear your hair out.