Cutaneous manifestations of Thyroid Disease

Thyroid hormones profoundly influence the growth and differentiation of epidermal and dermal tissues.
Abnormal levels of thyroid hormone produce striking changes in the texture of the skin, hair, and nails.
Some of the associated skin alterations in thyroid disease are the result of a deficiency or a high toxic level of tissue thyroid hormone.
Other skin disorders that are considered to be autoimmune in etiology may coexist with thyroid disease such as vitiligo and alopecia areata, but are not directly related to thyroid hormone function.
Findings such as pretibial myxedema are caused by circulating autoimmune -globulin, which acts as a thyroid-stimulating hormone.
Hyperthyroidism may be caused by Graves disease, subacute thyroiditis, toxic goiter, and thyroid carcinoma.
Hypothyroidism may be caused by iodine deficiency (cretinism), Hashimoto thyroiditis, pituitary dysfunction with thyroid-stimulating hormone deficiency, and surgical or radiation ablation of the thyroid.
Patients with thyroid disease may be hyperthyroid at one point in their clinical course and hypothyroid at another time.

Clinical Manifestations ⬆ ⬇

Hyperthyroid skin changes result from a hypermetabolic state (e.g., warm, moist, flushed skin) during the active thyrotoxic stage of thyroiditis, active Graves disease, or in patients with toxic goiters. These skin changes may gradually resolve when the patient returns to a euthyroid state.
Hyperthyroid skin lesions may include the following:
- Warm, moist, and velvety skin.
- Alopecia with diffuse hair loss.
- Nail changes with onycholysis (Plummer nails).
- Hyperpigmentation.
- Pretibial myxedema lesions—flesh-colored or erythematous waxy, infiltrated, translucent plaques (Figs. 34.7 and 34.8).
Graves disease lesions (pretibial myxedema) occur in up to 4% of patients with this disease. The skin lesions and eye lesions (exophthalmos, Fig. 34.9) usually do not resolve, even after treatment of the thyroid disease brings a return to a euthyroid state.
Hypothyroid skin changes (e.g., cool, dry skin) are related to the length and severity of the clinical hypothyroid state. These skin lesions gradually improve some months after the patient returns to a euthyroid state.
Hypothyroid skin lesions may include the following:
- Myxedema of the skin with generalized thickening and a dry, coarse feel, yellow skin secondary to carotenemia.
- Hair changes—coarse, sparse hair; lateral third of eyebrows lost.

Diagnosis ⬆ ⬇

Diagnosis of both hyperthyroid and hypothyroid disease is made by specific thyroid function tests.
Pretibial myxedema is often diagnosed in the clinical context of Graves disease; a skin biopsy should be performed if there is any doubt.

Other Information ⬆

Laboratory Evaluation

Elevated thyroid-stimulating hormone levels are the most sensitive screening test for hypothyroidism.
Serum thyroid hormone levels can be most accurately measured by obtaining free thyroxine and free triiodothyronine levels.
Antithyroglobulin antibodies and antithyroid microsomal antibodies are often positive in Graves disease and Hashimoto thyroiditis.
Long-acting thyroid stimulator is elevated in 50% of patients with Graves disease.
Skin biopsies in Graves disease show increased staining of hyaluronic acid with mucin stains in the reticular and papillary dermis.

Differential Diagnosis

Pretibial myxedema should be differentiated from other skin diseases such as:

Elephantiasis nostras verrucosa

Nonpitting edema, skin fibrosis, cobblestone-like plaques, and massive enlargement of the lower legs
A progressive cutaneous hypertrophy due to chronic lymphedema, characterized by repeated inflammatory episodes, long-standing lymphatic obstruction, stasis dermatitis, or low-grade recurrent cellulitis (Fig. 34.10)

Stasis Dermatitis (see Chapter 13: Eczema and Related Disorders)

Lichen Simplex Chronicus (see Chapter 13: Eczema and Related Disorders)

Lichen Amyloidosis

Lichen Planus (see Chapter 15: InflAMmatory Eruptions of Unknown Cause)

Management

Functional symptoms (e.g., increase or decrease in sweating, dry skin, hair and nail changes) of hyperthyroidism and hypothyroidism may improve after appropriate treatment of thyroid disease and return to a euthyroid state.
Treatment of pretibial myxedema lesions can be attempted with high-potency topical steroids and intralesional steroids, although the response is generally poor.