Which thyroid disorders are associated with xerosis (dry skin) and pruritus (itching)?

Thyroid Conditions Associated with Dry Skin and Itching

Hypothyroidism is the primary thyroid disorder that causes dry skin (xerosis) and itching (pruritus), while hyperthyroidism can also cause pruritus but typically presents with warm, moist skin rather than dryness. 1, 2, 3

Hypothyroidism and Skin Manifestations

Hypothyroidism directly causes dry, scaly, rough skin (xerosis) as a hallmark dermatologic manifestation. 2, 4 The mechanism involves:

• Decreased metabolic rate reduces eccrine gland secretion, leading to diminished skin moisture and characteristic dryness. 4
• Reduced capillary blood flow to the skin contributes to the pale, cool, dry appearance. 3
• Accumulation of glycosaminoglycans in the dermis can cause diffuse myxedema, further altering skin texture. 5

Additional Cutaneous Features of Hypothyroidism

Beyond xerosis, hypothyroidism presents with:

• Yellowish skin tone from increased carotene deposition in the dermis 4
• Follicular keratoses that may develop secondary eczema 5
• Delayed wound healing 5
• Dull, sparse hair due to prolonged anagen phase disruption 4, 5
• Nail growth abnormalities (onychodystrophy) 4, 3

Hyperthyroidism and Pruritus

Hyperthyroidism causes pruritus in some patients, but the skin is characteristically warm and moist rather than dry. 1, 3, 5 Key features include:

• Increased metabolic turnover with transcutaneous heat loss produces warm, sweaty skin 5
• Pruritus may occur with or without urticaria 5
• Fine tremor, tachycardia, and heat intolerance accompany the skin findings 1

Graves' Disease-Specific Manifestations

Pretibial myxedema (localized myxedema) can paradoxically occur in hyperthyroid states, particularly Graves' disease. 3, 5 This presents as:

• Bilateral, symmetrical thickening of pretibial skin 5
• When combined with exophthalmos and acropachy, forms the E.M.O. (exophthalmos-myxedema-osteoarthropathy) syndrome 5

Clinical Approach to Thyroid Testing in Pruritus

The British Association of Dermatologists explicitly recommends against routine thyroid function testing for isolated generalized pruritus unless additional clinical features suggest thyroid disease. 1, 6, 7 This is because:

• Only approximately 27% of patients with thyroid disease develop pruritus, making it an uncommon association. 6, 7, 8
• A retrospective study of 263 patients with pruritus found only 3 instances of associated thyroid disease over 3 years. 7

When to Test Thyroid Function

Test TSH and free T4 when pruritus occurs with:

• Cold intolerance, weight gain, constipation, fatigue (hypothyroidism) 1, 2
• Heat intolerance, weight loss, tremor, palpitations (hyperthyroidism) 1
• Delayed ankle reflexes, periorbital puffiness, coarse skin (hypothyroidism) 1
• Lid lag, fine tremor, warm moist skin (hyperthyroidism) 1

Treatment Considerations

Normalization of thyroid function with appropriate hormone replacement (levothyroxine for hypothyroidism) or antithyroid medications should improve pruritus if thyroid disease is truly causative. 6, 7, 4

First-Line Symptomatic Management

While addressing the underlying thyroid disorder:

• Apply emollients liberally and frequently, especially after bathing while skin is damp 1, 8
• Keep nails short to prevent excoriation 6
• Consider non-sedating antihistamines (loratadine 10 mg daily, cetirizine 10 mg daily, or fexofenadine 180 mg daily) for short-term use 6, 8

Critical Pitfall

Do not attribute all pruritus to thyroid disease—investigate other common causes including chronic kidney disease (affects 42-60% of dialysis patients), iron deficiency, liver disease, and hematological disorders. 1, 7 The association between thyroid disease and pruritus is uncommon, and other etiologies are often more likely. 7