Hypothyroidism happens when the thyroid gland does not produce enough thyroid hormone. The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. The most common form is Hashimoto's thyroiditis.

Hashimoto's thyroiditis occurs when:

• Immune system produces antibodies that attack cells of the thyroid gland, causing chronic thyroid swelling and loss of function
• Other causes:
  • 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 US)
  • Subacute thyroiditis—following a viral upper respiratory tract infection
  • Medical treatments— radiation to the head and neck or surgical removal of part of the thyroid gland (called subtotal thyroidectomy )
  • Medications (eg, lithium , iodine, alpha-interferons, thiourea, amiodarone , interleukins)
  • Certain diseases (eg, cancer or infection)
  • Pituitary adenoma —benign tumor of the pituitary gland

These factors increase your chance of developing hypothyroidism:

Risk factors include:

• Age: risk increases with age, especially over 65 years old
• Sex: more common in females
• Genetics: multiglandular autoimmune syndrome
• Ethnicity: Caucasian, Hispanic
• History of family members with hypothyroidism
• History of other autoimmune diseases:
  • Pernicious anemia
  • Type 1 diabetes
  • Underactive adrenal or parathyroid glands
  • Rheumatoid arthritis
  • Lupus

Tell your doctor if you have any of these risk factors.

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 with concentration
• Blurred vision
• Menstrual abnormalities or infertility

Symptoms of severe or prolonged cases include:

• Stupor or coma
• Slow heart rate
• Depressed breathing
• Hypothermia (low body temperature)
• Hoarseness

The doctor will ask about your symptoms and medical and family history, and perform a physical exam. To confirm the diagnosis, blood tests will be done, which include:

• Thyroid stimulating hormone (TSH)
• Free T4 and free T3
• Antibodies that attack the thyroid gland

In the early stages of Hashimoto's thyroiditis, there is no specific treatment. But, in most cases, you will end up developing hypothyroidism. Treatment includes:

• Medication to replace the thyroid hormones (eg, levothyroxine , triiodothyronine)
• High-fiber diet to reduce constipation
• Low-fat , low-calorie diet if you are overweight or obese