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What is an Underactive Thyroid?

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Hypothyroidism related image Photo: Getty Images

When a person has an underactive thyroid, or hypothyroidism, her thyroid does not produce enough of the thyroid hormones — triiodothyronine (T-3) and thyroxine (T-4) — which are involved in metabolism. While both men and women can have an underactive thyroid, women who are over age 50 are more likely to have the condition, according to the MayoClinic.com.

Several conditions can cause an underactive thyroid. MedlinePlus noted that the most common cause is an inflammation of the thyroid gland. When the thyroid becomes inflamed, its cells become damaged.

The autoimmune disorder, known as Hashimoto’s disease, may cause hypothyroidism, as the immune system mistakes the patient’s thyroid gland as a foreign object and attacks it. About 0.1 to 5 percent of adults in Western countries have this form of chronic thyroiditis, according to MedlinePlus.

Some medications may cause hypothyroidism. Medications that treat hyperthyroidism, or an overactive thyroid, such as methimazole or propylthiouracil, may cause hypothyroidism.

Lithium, a psychiatric medication used to treat disorders such as bipolar disorder, may affect thyroid function. Patients who take amiodarone may develop hypothyroidism.

Other forms of treatment may cause an underactive thyroid, such as radiation therapy or thyroid surgery. Patients who suspect their medications have contributed to an underactive thyroid should talk to their doctors and should not alter their medication unless under the direction of a doctor.

After pregnancy, some women may develop hypothyroidism. If the symptoms of hypothyroidism occur after a women became pregnant, it is called postpartum thyroiditis. Sheehan syndrome may also cause an underactive thyroid, noted MedlinePlus.

With Sheehan syndrome, a woman bleeds severely either during her pregnancy or during childbirth. This severe bleeding damages the pituitary gland, affecting its normal functioning. The pituitary gland is involved in thyroid gland function, so damage to the pituitary gland affects thyroid function.

A congenital defect may affect normal thyroid function.

Add a Comment3 Comments

Hashimoto's disease is a major cause of underactive thyroid function. In addition to causes of hypothyroidism listed by the article author there are about 22 thyroid defects that can lead to hypothyroidism too. You can read more about 22 thyroid defects here

January 3, 2012 - 7:23pm
EmpowHER Guest

This was a redidculous article. We could have looked this up on Google. It does not give symtoms and give very rare disorders as the cause. Perhaps they should have focused on environmental factors and/or the natural ways to handle hypothyroidsim rather than medication or blaming bizarre and very disorders. The article was not educational at all, it is first year medical school or Medical Assisting information. Did the author need a filler piece? or, was this just a reason to earn about $20.00 for the piece to run. Honestly, when I want medical news, I would like something a little more pertinent and educational.

January 2, 2012 - 9:17pm

Thyroid issues are getting to be more and more common.  Why is that?  Is it the environment, our diet?  Being a thyroid cancer survivor, this topic is of great interest to me.  It seems if you are living a clean life--eating well, exercising, not smoking, etc.  it still does not mean that you are not going to have thyroid problems. 

January 2, 2012 - 8:42pm
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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.


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