Dermatological features of thyroid disease

Overview

Skin findings in hypothyroidism vs hyperthyroidism

Feature	Hypothyroidism	Hyperthyroidism (Graves)
Skin texture	Dry, coarse, doughy - GAG accumulation	Warm, moist, smooth/velvety
Sweating	Decreased (anhidrosis)	Increased (hyperhidrosis)
Hair	Diffuse thinning, lateral eyebrow loss (Queen Anne's sign)	Diffuse thinning (rapid cycling)
Nails	Brittle, slow-growing	Onycholysis (Plummer's nails)
Oedema	Generalised non-pitting myxoedema	Pretibial myxoedema (Graves-specific)
Colour	Pallor, yellow tinge (carotenaemia)	Flushing, palmar erythema

⚠️

Pretibial myxoedema is a feature of Graves disease (autoimmune hyperthyroidism), NOT hypothyroidism - despite the name. It is caused by TSH receptor antibody stimulation of dermal fibroblasts causing GAG overproduction.

Investigations

🥇 First-line

•TSH, free T4, free T3 - confirms thyroid dysfunction

•Thyroid autoantibodies (TSH-R antibodies/TSI, anti-TPO, anti-thyroglobulin) - TSH-R antibodies elevated in Graves; correlate with pretibial myxoedema and acropachy

•If acropachy suspected: hand X-ray - periosteal new bone formation, spiculated 'frothy' pattern in metacarpals/phalanges

•Gold standard (if diagnostic uncertainty): skin biopsy of pretibial myxoedema - mucin (GAG) deposition on Alcian blue/colloidal iron staining, separation of collagen bundles

Management

•Hypothyroidism skin features: levothyroxine replacement - reverses dry skin, hair loss, GAG accumulation; emollients for symptomatic dry skin

•Hyperthyroidism/Graves: carbimazole (first-line UK) or propylthiouracil (pregnancy/first trimester), radioiodine, or thyroidectomy

•Pretibial myxoedema - first-line: high-potency topical corticosteroid under occlusion (e.g. clobetasol propionate) - reduces dermal fibroblast GAG production

•Pretibial myxoedema - second-line: intralesional triamcinolone for nodular/resistant lesions; compression bandaging as adjunct

📌

Thyroid acropachy has no effective treatment - periosteal changes are largely irreversible. Optimise thyroid control but counsel patients that resolution is unlikely.

Graves Disease - Extrathyroidal Triad

•Pretibial myxoedema - bilateral non-pitting indurated plaques/nodules over shins and dorsum of feet; pink-brown, waxy, 'peau d'orange' surface; firm, does not pit

•Graves ophthalmopathy - proptosis, lid lag (same TSH receptor on orbital fibroblasts)

•Thyroid acropachy - <1% of Graves patients; painless clubbing + soft tissue swelling of digits + periosteal new bone formation on X-ray (spiculated/frothy, metacarpals); does NOT resolve with treatment

💡

Pretibial myxoedema and thyroid acropachy can persist or appear even after the patient is rendered euthyroid, because they are driven by ongoing TSI antibody activity, not thyroid hormone levels.

Associated Autoimmune Skin Conditions

•Vitiligo - depigmented macules due to melanocyte destruction; associated with both Graves disease and Hashimoto's thyroiditis (shared autoimmune pathogenesis)

•Alopecia areata - well-demarcated patches of non-scarring hair loss; associated with autoimmune thyroid disease