Thyroid and Hair Loss: Symptoms & What to Test

If you’re shedding more hair than usual and wondering whether your thyroid is to blame, you’re not alone. thyroid and hair loss: symptoms & what to test is a question we hear often—because both low and high thyroid hormone can trigger diffuse thinning that looks like overall volume loss (not patchy bald spots). The good news: with the right labs and treatment, hair usually recovers—slowly, but steadily.

Thyroid and hair loss: symptoms & what to test — pass this guide to a friend who’s losing hair and isn’t sure why.

See also: Recovery Guide • Clinic Selection • Surgeon Selection

Thyroid and Hair: What Actually Happens?

Thyroid hormones help regulate the hair cycle. When levels are off, more follicles shift into telogen (resting) at once—known as telogen effluvium—causing excessive daily shedding without scarring. Once the underlying imbalance is corrected, follicles gradually re-enter growth. Expect improvement to lag therapy by 3–6+ months due to the hair cycle’s pace.

Symptoms to Watch (Beyond the Hair)

When low thyroid is the culprit (hypothyroidism)

Fatigue, dry/coarse hair, cold intolerance, constipation, weight gain, dry skin—often with diffuse thinning rather than discrete patches.

When thyroid is overactive (hyperthyroidism)

Anxiety, heat intolerance, palpitations, weight loss, tremor—sometimes with diffuse shedding. Autoimmune Graves’ disease may be suspected if there’s eye or skin involvement.

Patchy round/oval bald spots suggest alopecia areata, an autoimmune condition that occurs more often in people with autoimmune thyroid disease and needs a different workup/treatment.

Thyroid and Hair Loss: What to Test (the exact labs)

Use this checklist with your clinician. It balances thoroughness with evidence:

• TSH (Thyroid-Stimulating Hormone) — first-line screen.
  • High TSH → points toward hypothyroidism; check Free T4 from the same sample.
  • Low TSH → evaluate for hyperthyroidism with Free T4 ± Free T3.
• Free T4 (± Free T3)
  • Confirms low hormone in hypothyroidism and high hormone in hyperthyroidism; Free T3 is particularly helpful when hyperthyroidism is suspected.
• Thyroid antibodies (autoimmune clues)
  • TPOAb (± TgAb) for Hashimoto’s suspicion.
  • TSI/TRAb if Graves’ disease is suspected (sometimes alongside a radioactive iodine uptake/scan per clinician judgment).
• Iron studies if shedding is significant
  • Ferritin, iron, iron saturation, CBC—iron deficiency commonly coexists with diffuse shedding and can worsen recovery. Treating it helps hair regrowth once thyroid is corrected.
• Consider other targeted tests (case-by-case)
  • Vitamin D, zinc, B12 where diet, symptoms, or exam suggest deficiencies; dermatology and primary-care practice varies.
  • Scalp exam ± biopsy if diagnosis is unclear (e.g., to distinguish chronic telogen effluvium vs. other alopecias).

Timing Matters: When Hair Sheds vs. When it Regrows

Hair loss from thyroid dysfunction often appears months after the hormonal problem starts, and regrowth takes months after treatment begins. It’s common to notice shedding after starting correct therapy (the “catch-up” shed), which can be misattributed to medication. Stick with medically guided treatment unless your clinician advises otherwise.

Biotin can skew your thyroid labs (read this before testing)

High-dose biotin (often 5,000–10,000 µg in “hair & nails” supplements) can make labs falsely look hyperthyroid (TSH low, T3/T4 high). Most endocrine groups advise stopping biotin at least 48 hours before testing; some labs prefer a longer washout. Always tell your clinician/lab about supplements.

Treatment Basics (and What to Expect for Your Hair)

• Hypothyroidism: Standard therapy is levothyroxine; dose is individualized and monitored with TSH (and sometimes Free T4). With stable, appropriate dosing, systemic symptoms improve and hair typically thickens over months. Avoid over-replacement, which can worsen shedding and bone health.
• Hyperthyroidism: Antithyroid drugs (e.g., carbimazole, propylthiouracil), radioiodine, or surgery—your endocrinologist will tailor the plan. Rarely, antithyroid drugs themselves can contribute to diffuse shedding; clinicians weigh risks/benefits.
• Support the hair cycle: Correct iron deficiency, maintain adequate protein, and consider gentle hair care while waiting for regrowth. Many episodes of thyroid-related telogen effluvium self-resolve once triggers are addressed.

When to See a Dermatologist

Patchy hair loss, eyebrow loss, scalp discomfort or scarring, or ongoing shedding >6 months despite normalized thyroid labs. Dermatologists can confirm the pattern and rule out coexisting androgenetic alopecia or alopecia areata.

Hair Enhancement Resources & Guides

• How Genetics Influence Hair Loss — what you really inherit and what you can change.
• FUE vs FUT Hair Transplant — when surgery enters the plan.
• Effective Non-Surgical Hair Restoration Methods — evidence-based options you can start now.
• How to Choose a Hair Transplant Clinic — credentials, red flags, questions to ask.
• Hair Transplant Recovery Guide — A week-by-week timeline and aftercare tips.

FAQ: Thyroid and Hair Loss: Symptoms & What to Test

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Bottom Line + Next Steps

If you suspect a thyroid link, bring this lab list to your clinician: TSH → Free T4 (± Free T3), TPOAb (± TgAb), TSI/TRAb if hyperthyroid, plus ferritin/iron studies when shedding is significant. Correct the root cause, give hair time to cycle back, and avoid biotin before labs. If thinning persists, see a dermatologist to rule out other causes and discuss adjunct options like PRP or, for pattern loss, medical therapy and (later) transplantation. thyroid andhair loss: symptoms & what to test doesn’t have to be a mystery—test smart, treat the cause, and track progress over months, not weeks. See top-rated clinics here.

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• British Thyroid Foundation: Hair loss & thyroid disorders (clear patient guide).
• Harvard Health: How thyroid problems are diagnosed (TSH-first approach).
• StatPearls (NCBI): Telogen effluvium evaluation (include TSH, iron studies).
• American Thyroid Association: Biotin can distort thyroid tests—pause before labs. thyroid.org