The thyroid produces two main hormones called T3 and T4. These hormones travel in your blood to all parts of your body controling the rate of many activities in your body, including how fast you burn calories and how fast your heart beats. These activities together are known as your body's metabolism.
A thyroid that is working right will produce the right amounts of hormones needed to keep your body's metabolism working at a rate that is not too fast or too slow.
What is Hypothyroidism?
Hypothyroidism, also called underactive thyroid, is when not enough thyroid hormone is made. The most common cause of hypothyroidism in the United States is Hashimoto's thyroiditis. Hashimoto's thyroiditis is an autoimmune disease, in which the immune system mistakenly attacks the thyroid and damages it so that it does not make enough hormones. Hypothyroidism also can be caused by:
- Treatment of hyperthyroidism
- Radiation treatment of certain cancers
- Thyroid removal
- In rare cases, problems with the pituitary gland can cause the thyroid to be less active
Symptoms of Hypothyroidism
Symptoms tend to develop slowly, often over several years. At first, you may just feel tired and sluggish. Later, you may develop other symptoms of a slowed down metabolism, including:
- Weight gain, even though you are not eating more food
- Increased sensitivity to cold
- Constipation
- Muscle weakness
- Joint or muscle pain
- Depression
- Fatigue (feeling very tired)
- Pale dry skin
- A puffy face
- A hoarse voice
- Excessive menstrual bleeding
In addition to these symptoms, people with hypothyroidism may have high blood levels of LDL (bad) cholesterol, which can increase your risk for heart disease.
Source: U.S. Department of Health and Human Services