Why does hypothyroidism cause dry skin?

What does thyroid hormone do in your skin?

Thyroid hormones regulate metabolism, meaning how cells use energy. Skin is one of their target organs, not just a surface that happens to look different when hormone levels fall. Skin cells have receptors that respond directly to thyroid hormone, helping regulate their growth and normal function.23

Several changes contribute to the dryness:

• Skin renewal and shedding change. Thyroid hormone helps regulate keratinocytes, the cells that build the outer skin layer. Laboratory research suggests that low thyroid hormone reduces an enzyme involved in shedding old surface cells.
• Barrier formation is affected. Thyroid hormone helps the outer skin layer form its protective barrier. Hypothyroidism may interfere with that process, contributing to dry, scaly skin.
• Sweating decreases. Reduced sweating is a recognised feature of hypothyroidism and accompanies the dry skin.

The dryness can be more pronounced and persistent than ordinary winter dryness. Very dry skin can resist the usual skincare routine, which is an awkward limit for a cupboard full of promises.4

What other changes should you look for?

Skin can look pale and feel cool, with fine scales or deeper cracks. Hair can become coarse, dry and brittle, and nails can become fragile or grow slowly. Thinning at the outer edges of the eyebrows is another possible clue. Dry skin alongside tiredness, constipation, feeling unusually cold or unexplained weight gain is a reason to discuss thyroid testing with your doctor.356

Hashimoto's thyroiditis is the most common cause of hypothyroidism. It is an autoimmune condition, meaning the immune system attacks the thyroid. Other forms of thyroid inflammation can also lower hormone levels, sometimes temporarily and sometimes permanently.6

Does dry skin mean you have hypothyroidism?

Dry skin alone does not diagnose thyroid disease. A doctor considers your symptoms and examination, then decides whether blood tests are needed. The usual tests measure free T4, a thyroid hormone, and TSH, the hormone that signals the thyroid to make hormones. Thyroid antibody tests can help identify an autoimmune cause.567

What helps if your thyroid is the cause?

Treatment replaces the missing thyroid hormone, usually with levothyroxine. Skincare cannot replace missing thyroid hormone, however ambitious the packaging. Your prescriber chooses a dose to relieve symptoms and bring blood hormone levels back to normal. Most people with an underactive thyroid need ongoing treatment.2

When treatment starts, hormone levels may be checked every two to three months; after that, monitoring is usually at least yearly. Those checks guide treatment rather than setting a deadline for your skin to improve. Continue prescribed thyroid medicine even when you feel better. If dryness or other symptoms worsen, fail to improve or change during treatment, contact your prescriber rather than changing the dose yourself.27

Tell your prescriber about palpitations, shakiness, sweating or rapid weight loss during thyroid replacement treatment, because these can signal that the dose is too high. Chest pain or a rapid heartbeat also needs medical attention.27