Thumbnail image of: Thyroid and Parathyroid Glands: Illustration

Hypothyroidism (Low Thyroid Level)

What is hypothyroidism?

Hypothyroidism is when your thyroid gland does not make enough thyroid hormone.

Your thyroid gland is in the lower front of your neck. This gland takes iodine from the food you eat to make thyroid hormones. Thyroid hormones are chemicals that control the way your body turns the food you eat into energy and how fast (or slow) your body uses that energy. They also control body functions such as temperature, heart rate, and appetite.

Mild hypothyroidism may cause no symptoms. Without treatment, however, the disease can cause heart problems or problems with memory and thinking.

Anyone can have low thyroid levels, but it happens most often in women over age 40.

What is the cause?

Low thyroid levels may be caused by:

  • Thyroiditis, which is swelling and irritation of the thyroid gland. There are different types of thyroiditis. Hashimoto’s thyroiditis is the most common type. It is an autoimmune disease, which means it causes your body to mistakenly attack your own tissue. Thyroiditis may also be caused by a virus or bacteria. It also happens to some women after giving birth. Sometimes the cause of thyroiditis is unknown.
  • Radiation treatment, which can destroy the thyroid gland and its ability to make thyroid hormone. This may happen if you take radioactive iodine for an overactive thyroid gland, or if you have radiation treatment for cancer of the jaw, neck, or upper body.
  • Medicine taken to treat high thyroid levels. If you take medicine for a thyroid problem, you should have your thyroid levels checked as often as recommended by your provider. Also make sure your healthcare provider knows about any other medicines, herbs, or supplements that you are taking. Some medicines and supplements change how thyroid medicine works.
  • Surgery to remove all or part of your thyroid gland for another thyroid problem
  • Inherited thyroid problems, which means that they are passed from parents to children through their genes. Genes are inside each cell of your body. They contain the information that tells your body how to develop and work.

What are the symptoms?

Symptoms may slowly get worse for months or even years. Symptoms may include:

  • Puffiness or swelling in the face and neck
  • Feeling tired all the time
  • Depression
  • Weakness
  • Constipation
  • Weight gain
  • Feeling cold a lot of the time
  • Heavy, long menstrual periods
  • Dry skin, hair, or nails
  • Hoarse voice
  • Trouble concentrating or remembering

After several months or years of untreated hypothyroidism, you may be slow to talk and move, be less alert, and feel drowsy much of the time. It may also cause heart damage.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and medical history and examine you. You will have blood tests.

How is it treated?

Your healthcare provider will prescribe thyroid hormone medicine. After starting treatment, you will have blood tests to be sure you are getting the right amount of thyroid hormone. It may take several weeks to find the right dosage. Once the correct dosage is found, your thyroid hormone level will need to be checked every few months. Too much or too little hormone replacement can cause heart problems and weak bones.

Usually low thyroid levels start getting better within a week after you start taking the medicine. You will most likely need to take the medicine every day for the rest of your life.

How can I take care of myself?

Follow the full course of treatment prescribed by your healthcare provider. Don’t stop taking your medicine or change the way you take it unless your provider tells you to.

You will need to have blood tests to check your thyroid hormone level every few months for the rest of your life. The tests can help make sure you are getting the right amount of medicine.

Ask your healthcare provider:

  • How and when you will hear your test results
  • How long it will take to recover
  • If there are activities you should avoid and when you can return to your normal activities
  • How to take care of yourself at home
  • What symptoms or problems you should watch for and what to do if you have them
  • Make sure you know when you should come back for a checkup. Keep all appointments for provider visits or tests.
Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2015-01-28
Last reviewed: 2015-01-28
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

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