Skin problems associated with thyroid disease
Overactivity and underactivity of the thyroid gland may result in alterations in skin, hair or the nails. This may be as a result of the abnormal level of thyroid hormone, or a consequence of an underlying condition.
Thyrotoxicosis (overactive thyroid gland)
Excess thyroid hormone (thyroxine) may be due to:
- Graves disease (an autoimmune condition in which there are antibodies that activate the thyroid gland resulting in goitre and, often, protruding eyes)
- A thyroid nodule
- Excessive intake of thyroxine medication.
Thyrotoxicosis results in an increase in metabolic rate. This may result in:
- Smooth, moist, warm skin
- Flushing of face and hands
- Overgrown nails (acropachy, clubbing), which may lift off the nail bed (onycholysis)
- Fine soft thinned scalp hair
- Generalised itching (pruritus)
- Increased skin pigmentation
Graves disease can be associated with other autoimmune conditions, including vitiligo.
Pretibial myxoedema or thyroid dermopathy affects 5% of patients with Graves disease. It may appear before, during or after the thyrotoxic state and is sometimes associated with an underactive thyroid. Pretibial myxoedema presents with a swollen and lumpy appearance over the shins and sometimes also affects the feet. The skin may be discoloured pink or purple, with prominent hair follicles. This is known as ‘peau d'orange’ (orange-peel) appearance. It may instead look warty or ‘verrucous’.
Pretibial myxoedema is a form of diffuse mucinosis. The thickened and inelastic skin is filled with excessive hyaluronic acid and chondroitin sulphate. These are acid mucopolysacharides (glycosaminoglycans).
The same material is deposited behind the eyes resulting in protrusion and lid lag on movement of the eyeballs.
Pretibial myxoedema is thought to be caused by thyroid-stimulating immunoglobulin (autoantibodies) but this is not proven.
The name 'pretibial myxoedema' is misleading as although common in front of the tibea bone, it may occur in other sites, and it is not caused by mucus (myxoid tissue).
Hypothyroidism (underactive thyroid gland)
An underactive thyroid gland may be also be due to autoimmune diseases:
- Idiopathic hypothyroidism – a condition of unknown cause in which the thyroid undergoes a destructive and scarring process
- Hashimoto's thyroiditis – an inflammatory condition with the same result.
An underactive thyroid may result in:
- Cold, pale and dry skin
- Delayed wound healing
- A yellowish hue to the skin due to carotenaemia
- Sparse, brittle hair which comes out in handfuls
- Slow growing ridged and brittle nails
- Myxoedema resulting in puffy eyelids and hands – another presentation of mucinosis.