Definition
The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hypothyroidism happens when the thyroid gland does not produce enough thyroid hormone. The most common form of hypothyroidism is Hashimoto's thyroiditis.
Causes
Hashimoto's thyroiditis occurs when the immune system produces antibodies that attack cells of the thyroid gland. This causes thyroid swelling and loss of function. Other causes include:
- Idiopathic thyroid atrophy—destruction of thyroid tissue for unknown reasons
- Iodine deficiency—when a thyroid gland needs iodine to produce thyroid hormone (rare in the United States)
- Subacute thyroiditis—following a viral upper respiratory tract infection
- Medical treatments— radiation to the head and neck or surgical removal of the thyroid gland (called subtotal thyroidectomy )
- Medicines (such as lithium , iodine, amiodarone , interleukins)
- Certain diseases (such as cancer or infection)
- Pituitary adenoma —benign tumor of the pituitary gland
Risk Factors
Risk factors that can increase your chance of developing hypothyroidism include:
- Age: over 65 years old
- Sex: more common in females
- Ethnicity: Caucasian, Hispanic
- History of family members with hypothyroidism
- History of other autoimmune diseases:
Symptoms
Years may pass before you notice symptoms.
Symptoms include:
- Fatigue
- Weakness
- Coarse, brittle hair; hair loss
- Facial puffiness
- Dry skin
- Swollen hands or feet
- Cold intolerance
- Weight gain
- Constipation
- Achy feeling all over
- Depression and irritability
- Memory loss
- Difficulty concentrating
- Blurred vision
- Menstrual abnormalities or infertility
Symptoms of severe or long-term cases include:
- Coma
- Slow heart rate
- Depressed breathing
- Hypothermia (low body temperature)
Diagnosis
The doctor will ask about your symptoms and medical and family history. A physical exam will be done. To confirm the diagnosis, blood tests will be done, which include:
- Thyroid stimulating hormone (TSH)
- Free T4 and total T3
- Antibodies that attack the thyroid gland
