What could be causing my excessive hair loss, especially when washing and blow-drying, given my recent start of levothyroxine and switch in medications?

Evaluation of Recent-Onset Hair Loss with Medication Changes

Your hair loss is most likely telogen effluvium triggered by either inadequately controlled thyroid disease or the recent medication switch to Mirena, and you should obtain laboratory testing for TSH, ferritin, vitamin D, and zinc levels to identify the underlying cause. 1

Understanding the Timeline and Likely Causes

Your 2-week history of excessive hair loss coincides with two major medication changes occurring within the past 3 months, making drug-induced or hormone-related telogen effluvium the primary consideration 2, 3:

• Levothyroxine (3 months): The FDA label specifically notes that "partial hair loss may occur rarely during the first few months of levothyroxine sodium tablets therapy, but this is usually temporary" 4. However, hair loss can also indicate inadequate thyroid replacement or ongoing thyroid dysfunction 1

• Ryeqo to Mirena switch (2 months): Hormonal contraceptive changes commonly trigger telogen effluvium, with hair loss typically appearing 2-3 months after the hormonal shift 2, 3

Diagnostic Workup

Obtain the following laboratory tests immediately 1:

• TSH and free T4: To verify adequate thyroid replacement and rule out persistent hypothyroidism as the cause
• Ferritin: Iron deficiency is a common reversible cause of diffuse hair loss
• Vitamin D levels: Deficiency contributes to hair follicle dysfunction
• Zinc levels: Deficiency can exacerbate hair loss

The ESMO guidelines specifically recommend this laboratory panel when evaluating endocrine therapy-related alopecia, and these same principles apply to your hormonal medication changes 1.

Clinical Examination Points

Look for these specific features to narrow the diagnosis 1:

• Pattern of loss: Diffuse thinning across the entire scalp suggests telogen effluvium from medications or thyroid disease, while crown-predominant thinning with frontal/bitemporal recession suggests hormonal (endocrine) alopecia 1
• Hair pull test: Gently pull 50-60 hairs; if >6 hairs come out easily, this confirms active telogen effluvium 5
• Scalp examination: Normal-appearing scalp without inflammation or scaling rules out tinea capitis, scarring alopecia, and alopecia areata 1
• Exclamation mark hairs: Short broken hairs at the margins would suggest alopecia areata rather than medication-induced loss 1

Most Likely Diagnosis and Management

Telogen effluvium from hormonal medication changes is the most probable diagnosis 2, 5, 3. This condition:

• Typically begins 2-3 months after the triggering event (matching your timeline with the Mirena insertion) 2, 3
• Causes diffuse hair shedding that is most noticeable during washing and styling 5
• Is self-limited and resolves within 3-6 months once the trigger is removed or stabilized 2, 5

However, inadequate thyroid replacement must be ruled out first 1. If your TSH is elevated or free T4 is low, your levothyroxine dose needs adjustment before attributing the hair loss solely to the Mirena.

Treatment Approach Based on Laboratory Results

If TSH/T4 are abnormal 1:

• Optimize levothyroxine dosing first
• Recheck thyroid function in 6-8 weeks
• Hair regrowth typically begins 2-3 months after achieving euthyroid state

If thyroid function is normal and deficiencies are identified 1:

• Correct ferritin deficiency (target >40 ng/mL)
• Supplement vitamin D to normal range
• Correct zinc deficiency if present
• Consider biotin 2.5 mg daily, though evidence is limited 1

If all laboratory values are normal 2, 5:

• The hair loss is likely telogen effluvium from the Mirena transition
• Reassure that this is self-limited and will resolve in 3-6 months
• No specific treatment alters the course; the hair follicles are not permanently damaged 2, 3
• Avoid harsh styling, heat, and chemical treatments during recovery 5

Critical Pitfall to Avoid

Do not assume the levothyroxine is adequately dosed without checking TSH and free T4 1. Undertreated hypothyroidism is a reversible cause of hair loss that will not improve until thyroid function is optimized. The timing of your levothyroxine initiation (3 months ago) makes inadequate replacement a strong consideration, as hair loss from persistent hypothyroidism can manifest at this timeframe 4, 5.

Expected Timeline for Recovery

Once the underlying cause is identified and corrected 2, 5, 3:

• Active shedding should decrease within 2-3 months
• New hair growth becomes visible at 3-4 months
• Full recovery of hair density takes 6-12 months
• Hair grows approximately 1 cm per month during recovery 1