The Link Between Thyroid Disease and Hair Loss

Hair texture can also change with thyroid dysfunction

We all lose hair on a routine basis, shedding as many as 100 hairs per day across the entire scalp. Normally, these hairs are replaced with time. If you have thyroid disease, however, you may experience hair loss more than others—so much so that your hair on the whole looks to be thinning. Having autoimmune thyroid disease in particular also puts you at greater risk for alopecia areata—excessive and rapid hair loss in specific parts of the scalp that can advance to baldness and also effect other parts of the body, like the eyebrows. Most cases of thyroid-related hair loss are temporary and treatable.

The Life Cycle of Hair

To identify the difference between normal hair loss and that related to a thyroid condition, it's important to understand the three phases of the hair life cycle. These include:

life cycle of a hair
Illustration by Emily Roberts, Verywell
  • Anagen phase: This is the growth phase, meaning your hair is actively growing; the rate of growth and duration depends on the type of hair and where it's located. At any given time, about 90 percent of the hair on your scalp is in the anagen phase.
  • Catagen phase: Hair then enters this "transition phase" during which hair stops actively growing. This lasts about three weeks and involves less than 1 percent of the hairs on your scalp at a time.
  • Telogen phase: During this last phase, a hair prepares to shed; it is then pushed out of the follicle and falls out. Typically, about 50 and 150 telogen hairs are shed per day. These hairs are then replaced by new growth and the cycle begins again.

Symptoms

Thyroid-related hair loss and hair changes have some characteristic symptoms, including:

  • Diffuse hair loss/thinning across the whole scalp
  • Hair loss that occurs in discrete areas of the scalp, resulting in smooth, circular bald patches. Loss of body hair from areas other than your head. A unique and characteristic symptom of hypothyroidism is the loss of the hair on the outer edges of your eyebrows.
  • Changes in your hair's texture. With hypothyroidism, your hair may become dry or coarse; with hyperthyroidism, it can become extra soft and fine.

Hair Loss Patterns Can Differ

While overall thinning of hair is common in people with thyroid diseases, bald patches are specific to alopecia areata, an autoimmune disease that often, but not always, appears in conjunction with thyroid disease.

Causes

Thyroid diseases occur when the normal production of thyroid hormones is disrupted. The key hormones are triiodothyronine (T3) and thyroxine (T4). Because the thyroid contributes to a range of processes throughout the body, impaired thyroid function can stall hair growth. Related causes of hair loss include:

  • Alopecia areata: This is an autoimmune condition that often exists in conjunction with thyroid conditions. With alopecia areata, the immune system attacks the hair follicles, interfering with the normal growth process. Smooth, circular bald patches appear as a result.
  • Thyroid medications: The antithyroid drugs carbimazole and propylthiouracil may, in rare cases, lead to hair loss.

While prolonged thyroid disease may cause diffuse hair loss, it's important to note that with treatment of your thyroid dysfunction, regrowth will typically occur (although it may take months and it may be incomplete).

  • Other autoimmune diseases:  Lupus is an autoimmune condition linked to autoimmune thyroid disease that can cause hair loss. Lupus-related hair loss occurs through scarring on the scalp. The hair follicle is replaced by scar tissue, so hair loss is permanent.

Diagnosis

If you have already been diagnosed with thyroid disease, your doctor will likely suspect that this is what's causing you to lose your hair. If you have not been diagnosed with thyroid disease or another autoimmune condition, your provider may use tests typically used to diagnose potential underlying diseases (such as lupus).

Your doctor may also want to rule out other possible causes of hair loss, including:

  • Hormone imbalances (such as can occur during menopause)
  • Nutritional deficiencies: not getting enough protein or iron can be a culprit in some cases
  • Medication side effects: Certain drugs, including blood thinners and those used to treat high blood pressure, can sometimes cause hair loss.

Treatments

thyroid-related hair loss
Illustration by JR Bee, Verywell

Treatment for thyroid-related hair loss usually involves being properly medicated for the condition. In most cases, getting your thyroid hormones adjusted will reverse the hair loss, though it may take several months for the hair to grow back.

Your doctor may also suggest you try one of the following medications to promote more rapid hair growth:

  • Rogaine (Minoxidil): This is a topical solution that is applied to the scalp; it is available without a prescription. 
  • Propecia (Finasteride) is a prescription drug taken in pill form that is used mostly to treat male pattern baldness. (It cannot be used by women who are pregnant or considering pregnancy.)

A Word From Verywell

Losing your hair can be distressing, but if it is caused by thyroid disease it is most likely reversible. In the meantime, try to stave off further hair loss by treating your hair gently. Avoid brushing it excessively, using harsh coloring products, and hairstyles that pull on the hair (such as a tight bun). If you feel self-conscious about having thin hair or bald patches, consider wearing a scarf or wig while your hair grows back.

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