What are the causes of hair loss in patients with type 2 diabetes taking Glucagon-like peptide-1 (GLP-1) receptor agonists or Dipeptidyl peptidase-4 (DPP-4) inhibitors?

Hair Loss with GLP-1/GIP Medications

Direct Answer

Hair loss is not a direct pharmacological side effect of GLP-1 receptor agonists or DPP-4 inhibitors, but rather occurs as a secondary consequence of rapid weight loss (telogen effluvium) or nutritional deficiencies from reduced caloric intake. 1

Understanding the Mechanism

The comprehensive adverse event profiles from over 20,000 patients across multiple trials do not list hair loss as a documented side effect of GLP-1 receptor agonists. 1 The established adverse effects are predominantly gastrointestinal (nausea, vomiting, diarrhea, constipation), along with rare but serious risks including pancreatitis, gallbladder disease, and thyroid concerns. 1

The hair loss you're experiencing is most likely telogen effluvium triggered by rapid weight loss, not a direct drug effect. 1 When patients lose weight quickly—as commonly occurs with semaglutide (14.9% weight loss) or tirzepatide (20.9% weight loss)—the metabolic stress can push hair follicles into the resting (telogen) phase prematurely. 2

Primary Causes to Investigate

Rapid Weight Loss (Most Common)

• Telogen effluvium occurs when significant weight loss (typically >5% body weight in 3 months) triggers hair follicles to enter the resting phase. 1 This is a physiological response to metabolic stress, not a medication toxicity.
• The hair loss typically begins 2-3 months after starting the medication, coinciding with the period of most rapid weight loss. 1

Nutritional Deficiencies (Second Most Common)

• Reduced caloric intake combined with gastrointestinal side effects (nausea, vomiting) can lead to protein, iron, zinc, and biotin deficiencies. 1
• GLP-1 receptor agonists suppress appetite and delay gastric emptying, which may inadvertently reduce nutrient absorption even when patients attempt to eat adequately. 3

Underlying Thyroid Dysfunction (Must Rule Out)

• Check thyroid function (TSH, free T4) to exclude hypothyroidism as a contributing factor. 1 While GLP-1 receptor agonists don't typically cause thyroid dysfunction, GLP-1 receptors are expressed in thyroid tissue, and patients with pre-existing thyroid disease may experience changes. 2
• This is particularly important since you mentioned the patient has hypothyroidism—ensure thyroid hormone replacement is optimized. 2

Diagnostic Workup

Order the following laboratory tests to identify reversible causes:

• Complete blood count (CBC) to assess for anemia 1
• Ferritin and iron studies (iron deficiency is a common cause of telogen effluvium) 1
• Thyroid function tests (TSH, free T4) 1
• Comprehensive metabolic panel to assess nutritional status 1
• Zinc and vitamin D levels if clinical suspicion is high 1
• Total protein and albumin to assess overall nutritional status 1

Management Strategy

Nutritional Optimization

• Ensure protein intake of at least 0.8-1.0 g/kg/day, emphasizing high-quality protein sources at each meal. 1 This is critical because rapid weight loss often results in inadequate protein intake.
• Supplement with a comprehensive multivitamin containing iron, zinc, biotin, and B vitamins. 1
• Consider adding resistance training to preserve lean body mass, which may help mitigate metabolic stress. 2

Medication Adjustment Considerations

• Slowing the rate of weight loss by reducing the GLP-1/GIP medication dose may help, but this must be balanced against glycemic control and cardiovascular benefits. 1 Gradual dose titration minimizes gastrointestinal side effects and may allow better nutritional intake. 3
• If hair loss is severe and distressing, discuss with the patient whether temporarily reducing the dose (e.g., from semaglutide 2.4mg to 1.7mg weekly) is acceptable while optimizing nutrition. 2

Reassurance and Timeline

• Telogen effluvium is self-limited and typically resolves within 6-9 months once the triggering factor (rapid weight loss) stabilizes. 1 Hair regrowth should begin once weight loss plateaus and nutritional status improves.
• Continue the GLP-1/GIP medication if glycemic control or cardiovascular benefits are significant, as the hair loss is not a sign of drug toxicity. 1

Common Pitfalls to Avoid

• Do not discontinue the GLP-1/GIP medication solely for hair loss without first optimizing nutrition and ruling out other causes. 1 The cardiovascular and metabolic benefits often outweigh this temporary cosmetic concern.
• Do not assume hair loss is a direct drug effect—it is almost always secondary to rapid weight loss or nutritional deficiency. 1
• Do not overlook thyroid dysfunction, especially in patients with pre-existing hypothyroidism. 1 Ensure thyroid hormone replacement is adequate before attributing hair loss to the GLP-1/GIP medication.

Special Considerations for DPP-4 Inhibitors

DPP-4 inhibitors (such as sitagliptin, linagliptin) have minimal effect on weight and are therefore much less likely to cause hair loss compared to GLP-1 receptor agonists. 3 If a patient on a DPP-4 inhibitor reports hair loss, investigate other causes more aggressively, as the medication is unlikely to be the culprit. 3