Thyroid hair loss in London: the panel that catches it and the recovery timeline

Thyroid disease is the single most-missed medical cause of hair loss in London. Patients come in with three months of shedding, having been told by GPs that their thyroid is 'normal' — because TSH is 3.8 and the lab's cut-off is 4.5. Meanwhile, at TSH 3.8, hair is measurably affected.

This guide walks you through the panel to insist on, the interpretation to expect, and what the recovery actually looks like — because thyroid hair loss is one of the few genuinely reversible causes of diffuse hair thinning, provided you catch it and treat it properly.

How thyroid hormones affect hair

Thyroid hormones (T4 and T3) regulate the anagen phase of the hair cycle. Too little (hypothyroidism) prolongs telogen and shortens anagen — follicles rest longer, grow slower, produce coarser dry hair, and eventually thin diffusely. Too much (hyperthyroidism) accelerates the entire cycle — hair sheds faster, becomes finer, and thins.

Both endpoints look identical clinically — diffuse thinning, worst at the temples and crown, no scarring, preserved follicular openings on trichoscopy. Without bloods, you cannot tell hypo from hyper.

The right panel

The minimum useful hair-focused thyroid panel:

• TSH — screening hormone. Target 1–2.5 mIU/L for hair (lab 'normal' extends to 4.5).
• Free T4 — active circulating thyroxine. Low-normal in subclinical hypothyroid.
• Free T3 — the biologically active hormone at the tissue level. Often missed on NHS panels.
• TPO antibodies (anti-thyroid peroxidase) — positive in Hashimoto's.
• Thyroglobulin antibodies — positive in Hashimoto's, sometimes in Graves'.
• TSH receptor antibodies (TRAb) — positive in Graves' hyperthyroidism.
• Reverse T3 — useful in complex cases where symptoms don't match TSH; not routine.
• Alongside: FBC, ferritin (target >70 μg/L), vitamin D (>75 nmol/L), B12, folate.

Hypothyroid hair: how it presents

Diffuse thinning, dry coarse texture, slow growth. Classic finding: loss of the outer third of the eyebrow (Queen Anne's sign). Skin is dry, hair may be brittle. Nails often ridged. Patients report fatigue, cold intolerance, constipation, weight gain, low mood, brain fog.

In London, most cases are autoimmune (Hashimoto's). Treatment is levothyroxine daily, dose titrated to a hair-focused TSH target of 1–2.5. NHS commonly leaves patients at TSH 3–4 — flag hair concerns explicitly to your GP or ask for private endocrinology if hair matters.

Hyperthyroid hair: how it presents

Diffuse thinning, fine soft texture, faster growth cycle but shorter shafts. Skin is warm, sometimes moist. Patients report anxiety, palpitations, heat intolerance, weight loss, tremor, altered menstrual cycle.

Autoimmune cause (Graves') is most common in London under-50s. Treatment is antithyroid drugs (carbimazole, propylthiouracil), radioactive iodine or thyroidectomy. Hair typically recovers as thyroid function normalises — but expect a telogen effluvium shed during the transition period as the cycle re-synchronises.

The levothyroxine shed

Almost every patient who starts levothyroxine — or has a dose change — experiences a telogen effluvium shed 6–14 weeks later. This is expected. It is the hair cycle re-setting as the body normalises. It resolves in 3–6 months, and the resulting hair quality is better than before.

The mistake is to interpret this shed as levothyroxine failure and stop or reduce the dose. Continue treatment, adjust to target TSH, and expect visible density recovery by month 6–9.

When to escalate

If your TSH is at target (1–2.5), free T4 and T3 are mid-range, antibodies are being monitored, ferritin is >70, vitamin D >75, and you're still shedding at 9 months — the hair loss is not primarily thyroid-driven. Revisit the differential: coexisting pattern loss, chronic telogen effluvium, medication effect, or an evolving autoimmune condition (alopecia areata, FFA).

For London patients: private endocrinology consult £250–£450, hair-focused trichology consult £150–£300, and the two coordinated is often the fastest route to a stable plan.