Hypothyroidism: Can the Medication Synthroid Cause Hair Loss?

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Both an overactive thyroid and an underactive thyroid can cause hair loss. In fact, hair loss is a fairly common symptom of hypothyroidism or underactive thyroid. But you may also wonder: Can Synthroid (levothyroxine), a medication that's used to treat hypothyroidism (as well as an enlarged thyroid gland and thyroid cancer) also cause hair loss?

Synthroid and Hair Loss

If your thyroid disease is not being well controlled on Synthroid, it is possible that you will continue to have problems with hair loss.

It means that you are either not getting enough of the medication or you're getting too much. So if you're taking Synthroid and you're still experiencing hair loss, make an appointment with your doctor to discuss the problem and see if you might be able to adjust your dosage.

Sometimes, generic versions of Synthroid vary oh-so-slightly in the amount of thyroid hormone that they contain and even this small difference can affect how well your thyroid condition is controlled.

Other Causes of Hair Loss

It is important for your doctor to review all of your medications and evaluate you for other conditions that could cause hair loss, such as anemia, diabetes, and other hormonal problems.

Also: Consider seeing a dermatologist, who can do a skin (usually a scalp) biopsy to see whether you have any underlying skin disease. 

More Information About Underactive Thyroid (Hypothyroidism)

Underactive thyroid or hypothyroidism occurs when your thyroid gland doesn't make enough thyroid hormone.

In addition to causing hair loss, hypothyroidism can result in the following signs and symptoms:

  • Fatigue
  • Weight gain
  • Dry skin
  • Dry hair
  • Achiness
  • Cold sensitivity

Hypothyroidism is diagnosed by a primary care physician or specialist after blood is drawn and analyzed for hormone levels. If you're concerned that you may have hypothyroidism, ask your physician to test you.

Fortunately, treatment with daily thyroid hormone replacement (Synthroid) is very effective. Many people with hypothyroidism live long and healthy lives. Untreated hypothyroidism, however, can contribute to heart disease, goiter, and pregnancy complications, as well as a rare, life-threatening condition called myxedema coma.

More Information About Overactive Thyroid (Hyperthyroidism)

Overactive thyroid (hyperthyroidism) results from the excess production of thyroid hormone. Symptoms of overactive thyroid usually manifest in people between the ages of 20 and 40. Women are 10 times more likely to be affected by hyperthyroidism. Causes of hyperthyroidism include medications (think amiodarone), thyroid nodules, and Graves disease (the most common cause).

In addition to hair loss, other symptoms of hyperthyroidism include the following:

  • Trouble sleeping
  • Mood swings
  • Heat sensitivity
  • Heart palpitations
  • Trembling
  • Weight loss
  • Fatigue
  • Weakness
  • Swelling of the neck

Symptoms of hyperthyroidism can be quite uncomfortable. If you believe that you are experiencing such symptoms, tell your doctor, who can evaluate you and order a blood test to check for thyroid levels if necessary.

Treatment of hyperthyroidism can involve medication, radioiodine, or surgery.

Medications can decrease the amount of thyroid hormone that's produced by your body. With radiation treatment, the thyroid gland is damaged and thus the amount of thyroid hormone that your body produces goes down. Finally, surgery can be performed to remove part or all of the thyroid. In people who have all of the thyroid removed, lifelong replacement of thyroid hormone is necessary.


Overactive Thyroid (Hyperthyroidism). NHS Choices. http://www.nhs.uk/conditions/thyroid-over-active/pages/introduction.aspx

Underactive Thyroid (Hypothyroidism). NHS Choices. http://www.nhs.uk/conditions/Thyroid-under-active/Pages/Introduction.aspx