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Underactive Thyroid

August 1, 2023

Underactive Thyroid

Underactive thyroid (also known as hypothyroidism), is a condition in which the thyroid gland is unable to make enough thyroid hormones to keep the body functioning as it normally would. The thyroid is a small butterfly-shaped gland located in the front of the lower neck. This gland is responsible for making hormones that are secreted into the bloodstream and travel throughout the body to regulate your metabolism. These hormones also help to control the body temperature and heart rate.

Underactive thyroid is a very common condition. According to the American Thyroid Association, over 12 percent of Americans will develop a thyroid condition during their lifetime. Hypothyroidism is also a treatable condition that can be well-controlled with medication and regular follow-ups with your healthcare provider.

Causes: The most common cause of underactive thyroid is an autoimmune condition called Hashimoto's disease. This is when the immune system attacks and destroys the thyroid. Other less common causes include inflammation or infection of the thyroid, medications such as lithium, or a history of thyroid surgery or radiation therapy.

Common symptoms. Symptoms can develop when the thyroid is underactive (hypothyroidism) or overactive (hyperthyroidism). This is why it is important to have the right amount of thyroid hormones in your body to keep the body functioning properly.

Symptoms of hypothyroidism:

  • Fatigue
  • Weight gain
  • Constipation
  • Depression
  • Increase sensitivity to cold
  • Dry skin
  • Thinning hair

Symptoms of hyperthyroidism:

  • Weight loss
  • Anxiety
  • Heat intolerance
  • Difficulty sleeping
  • Rapid heart rate
  • Shaky hands

Diagnosis: Since many of the symptoms of underactive thyroid are non-specific and are also seen in many other conditions, it can only be diagnosed by a healthcare professional. The diagnosis includes factors such as symptoms, family history, physical exam, and blood work. Blood tests show how much thyroid hormone is present in your body and helps your provider to determine if treatment is needed.

Treatment: Most patients with underactive thyroid will be treated with a medication called levothyroxine. It is a synthetic thyroid hormone that is taken once daily. If levothyroxine does not work for you, there are some other less commonly prescribed thyroid medications that can be tried. Since underactive thyroid is not curable, most people will remain on the medication lifelong. Your provider will likely check your levels again about a month or two after starting the medication to make sure your dosage is correct.

Managing your medication: Levothyroxine is best taken in the morning on an empty stomach, about 30-60 minutes before eating. However, making sure you consistently take your dose every day is most important. Do not stop taking the medication once your symptoms go away, or they will likely return after you stop taking it.

If you would like to learn more about underactive thyroid or the medications that can be used to treat it, your local Lewis pharmacist would be happy to answer any questions you might have.


  1. American Thyroid Association: Hypothyroidism

  1. Mayo Clinic: Hypothyroidism (underactive thyroid)

  1. Cleveland Clinic: Hypothyroidism

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