Hypothyroidism: Can Synthroid Cause Hair Loss?

Hair loss can result from hypothyroidism or hyperthyroidism.

man holding head in hands rear view
Hypothyroidism Hair Loss. Gary John Norman / Getty Images

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.

Synthroid and Hair Loss

If your thyroid disease is not being well controlled on Synthroid (levothyroxine), it is possible that you will continue to have problems with hair loss. It is not the Synthroid per se, it’s that you may not be getting enough of the medication or you may be getting too much.

If you suspect that you're taking either too little or too much Synthroid, please make an appointment with your physician for evaluation. Explain to your physician your concerns and ask any questions that you may have.

You indicate in your note that your dosage is not right and I agree with your thoughts about seeing an endocrinologist.

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

Other Medications and Hair Loss.

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

If getting your thyroid under control does not help with your hair loss, another option is to see a dermatologist who can do a skin (usually scalp) biopsy to see if you have any underlying skin disease.

A dermatologist is a physician who specializes in the treatment of skin conditions.

More Information About Underactive Thyroid

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

In addition to 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 your primary care physician or specialist after blood is drawn and analyzed for hormone levels. If you're concerned that you may be hypothyroid, please inform your physician. Your physician can better assess your signs and symptoms and order the appropriate tests.

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

Overactive thyroid (hyperthyroidism) results from the excess production of thyroid hormone. Symptoms of overactive thyroid usually manifest in people aged between 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 of hypothyroidism is Graves disease.

In addition to 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, please inform your physician. Your physician will better evaluate your signs and symptoms 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 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 their thyroid removed, lifelong replacement of thyroid hormone is necessary.

Bottom Line

Levels of thyroid hormone in your body, which are increased by Synthroid, can contribute to hair loss. If you are not able to control your thyroid levels using Synthroid, hair loss can occur. If you are experiencing hair loss and any other symptoms of hype- or hypothyroidism, like weight change or fatigue, it's important to make an appointment with your physician to have your hormone levels and medication regimen evaluated.


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

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