Thyroid and hair loss — the frequently overlooked cause
An overactive or underactive thyroid is one of the most common endocrine causes of diffuse hair loss—and is regularly overlooked in standard consultations. We explain which values are important, why "TSH within the normal range" is not enough, and what meaningful diagnostics can achieve.
Why the Thyroid Gland is So Important for Hair
Thyroid hormones (T3, T4) control the energy metabolism of every body cell — including the hair matrix cells responsible for hair production. In the event of a functional disorder, cell growth slows down, and the hair growth cycle gets out of sync: too many follicles enter the resting phase, and the anagen phase shortens.
The result is typically a diffuse hair loss over the entire scalp — without a receding hairline pattern, without sharp bald patches. This is precisely what makes diagnosis so difficult: It looks like a common telogen effluvium but has a treatable cause.
Overview of Thyroid Disorders
Hashimoto's Thyroiditis (Autoimmune Hypothyroidism)
- Most common thyroid disease in women
- Autoimmune: immune system attacks the thyroid gland
- Often a gradual progression over years, initially subclinical
- Hair loss often occurs even in the euthyroid early stage (TSH still normal!)
- Accompanying symptoms: fatigue, cold sensitivity, weight gain, concentration problems
Manifest Hypothyroidism (Underactive Thyroid)
- Elevated TSH, decreased fT4
- Dry, brittle hair
- Diffuse thinning
- Sometimes lateral thinning of the eyebrows (Hertoghe's sign)
- Fatigue, sluggishness, depressive mood
Hyperthyroidism (Overactive Thyroid)
- Decreased TSH, elevated fT3/fT4
- Common in Graves' disease (also autoimmune)
- Fine, thin hair
- Accelerated metabolism: weight loss, nervousness, palpitations, sweating
Postpartum Thyroiditis
- Occurs 2–6 months after birth
- Often biphasic: first hyperthyroidism, then hypothyroidism
- Exacerbates normal postpartum hair loss
Which Values Are Truly Important
A meaningful thyroid assessment includes more than just TSH:
Basic Diagnostics
- TSH — primary control hormone. Optimal range for hair loss patients: 0.5–2.5 µIU/ml (narrower range than the general normal range)
- fT3 (free triiodothyronine) — active thyroid hormone
- fT4 (free thyroxine) — storage/precursor hormone
- TPO antibodies (Anti-TPO) — marker for Hashimoto's, often elevated before TSH rises
- TG antibodies (Anti-TG) — supplementary autoimmune marker
- TSH receptor antibodies (TRAK) — if Graves' disease is suspected
Supplementary for Hair Loss
- Ferritin — should be > 70 ng/ml; many thyroid patients have accompanying iron deficiency
- Vitamin D (25-OH-D3) — often low in autoimmune diseases
- Selenium, zinc, B12 — important micronutrients for thyroid and hair
Why "TSH within the normal range" Is Often Not Enough
The general reference range for TSH (0.4–4.5 µIU/ml) is statistically broad and includes individuals with incipient Hashimoto's thyroiditis. For hair loss patients, we recommend a narrower evaluation: TSH values above 2.5 µIU/ml with positive antibodies indicate subclinical Hashimoto's thyroiditis, which is treatable.
What Thyroid-Related Hair Loss Looks Like
- Diffuse thinning over the entire scalp, often concentrated at the parting
- Increased hair shedding when brushing, washing, running hands through hair
- Texture changes: dry, dull, brittle hair
- Sometimes Hertoghe's sign: thinning of the outer eyebrows
- Slow regrowth
- No maximum pull test like in telogen effluvium, rather diffusely moderately positive
Diagnosis Steps
- Anamnesis: onset, course, accompanying symptoms, family history (Hashimoto's is often familial)
- Clinical examination: trichoscopy, hair structure assessment, eyebrows
- Laboratory diagnostics: complete thyroid panel including antibodies
- Imaging: thyroid sonography (typical findings in Hashimoto's)
- If findings are abnormal: referral for endocrinological co-treatment
Therapy
For Manifest Hypothyroidism
- Substitution with Levothyroxine (T4) by family doctor or endocrinologist
- Adjust TSH to approx. 1–2 µIU/ml
- Patience: hair improvement only after 6–9 months of full substitution
For Subclinical Hypothyroidism with Hair Loss
- Substitution may be useful with clearly elevated antibodies and TSH > 2.5
- Close monitoring every 3 months
- Accompanying optimization of selenium, vitamin D, iron
For Hyperthyroidism
- Thyrostatic therapy or other options (radioiodine, surgery) by endocrinologist
- Hair improvement after normalization of thyroid function
Supplementary Measures for Hair
- Micronutrient optimization based on lab results
- PRP sessions to accelerate recovery
- Topical growth stimulation as supplementary therapy
- Trichoscopy follow-up every 6 months
Special Situations
Thyroid + PCOS
Both conditions can occur simultaneously — they mutually amplify their effect on hair. A complete diagnosis of both axes is important.
Thyroid + Iron Deficiency
A common combination, especially in menstruating women. Both must be treated in parallel — resolving iron deficiency alone is not enough if the thyroid is subclinically underactive.
Pregnancy
Thyroid function should be closely monitored before and during every pregnancy — Hashimoto's in particular often worsens postpartum and affects both mother and child.
Frequently Asked Questions
My TSH is within the normal range — can my thyroid still be to blame?
Yes, this is even common. With TSH values between 2.5 and 4.5 µIU/ml and positive antibodies, subclinical Hashimoto's thyroiditis is often present and can cause hair loss. A complete panel with antibodies is diagnostically crucial here.
How long does it take for hair to improve after thyroid treatment?
Initial stabilization from month 3 of sufficient substitution, visible improvement from month 6–9, full recovery can take 12–18 months. Hair responds to thyroid function with a delay.
Should I take selenium if I have Hashimoto's?
Studies show that selenium supplementation (typically 100–200 µg/day) can lower anti-TPO antibodies. Have your selenium status checked in the blood before taking it — if levels are normal, the effect is minor. Excessive intake is not without risk.
Can I have a hair transplant if I have Hashimoto's?
Yes — provided thyroid function is stable (TSH 1–2 µIU/ml for at least 6–12 months) and the diffuse component is under control. In active, fluctuating Hashimoto's or accompanying autoimmune components, it is better to stabilize the underlying disease first.
Does Hashimoto's worsen the course of androgenetic alopecia?
Yes, it often combines. In women with FAGA and coexisting subclinical Hashimoto's, the effects are amplified. Treatment must address both axes.
Where is the best place to have my thyroid checked?
Ideally interdisciplinary: family doctor for basic diagnostics, endocrinology for complex cases, dermatological practice for hair analysis and connecting the findings. In our practice, we routinely discuss the thyroid axis with every female hair loss patient.