Causes

The most common cause of hypothyroidism is chronic thyroiditis, also called Hashimoto’s thyroiditis. Chronic thyroiditis occurs when the body’s immune system attacks thyroid tissue with antibodies and white blood cells—as if the tissue were foreign to the body. As a result, the thyroid produces less thyroid hormone and may become enlarged. (An enlarged thyroid is called a goiter.)

Hypothyroidism may also develop in people who have had thyroid surgery or radioactive iodine treatment for an overactive thyroid or in people who have received high doses of radiation for head and neck cancer or Hodgkin’s disease. Sometimes, infants are born without a thyroid gland or with a gland that does not function normally.

In rare cases, a condition called secondary hypothyroidism can also occur. Secondary hypothyroidism is caused when your pituitary gland, located at the base of your spine, does not produce enough thyroid-stimulating hormone.

Symptoms

Symptoms of hypothyroidism include:

• Fatigue
• Depression
• Feeling sluggish and cold
• Loss of interest in normal activities
• Dry and brittle hair
• Itchy, dry skin
• Constipation
• Muscle cramps
• Weight gain
• Memory problems
• Increased menstrual flow in women

Treatment

To determine if you have hypothyroidism, your doctor will take a blood sample and measure the levels of thyroid hormone and thyroid-stimulating hormone. Because hypothyroidism is an inherited condition, your family members may also develop thyroid problems and should have their thyroid function checked.

If you have hypothyroidism, your doctor will probably prescribe pure thyroxine. This medication is similar to what your body makes. Doses of thyroxine are adjusted until the blood levels of thyroxine and thyroid-stimulating hormone are normal. If the dose is adjusted properly, thyroxine is essentially free of allergic reactions and side effects.

Because thyroid failure may be an ongoing process to treat, the dosage may need to be adjusted over time. When the patient is elderly or has a heart condition, it’s important to start with a low dosage of thyroid hormone until the body gets used to normal thyroid hormone levels. Once the proper dosage is achieved, you should feel completely well. However, it’s important to have your thyroid hormone and thyroid-stimulating hormone levels checked each year.

If you have secondary hypothyroidism, the pituitary gland itself will be treated. You may also need to take medications.

Self-Care

If you are taking medication for hypothyroidism, you should continue to be aware of any symptoms you are experiencing. If you do not take enough thyroid hormone, you may be sluggish, feel cold, or experience mental dullness or muscle cramps. You may also have an elevated cholesterol level, which could increase your risk for heart disease.

If you take too much thyroid hormone, you may have symptoms of an overactive thyroid, such as nervousness, palpitations, insomnia, shaky hands, or feeling overheated. Too much thyroid hormone may also increase your risk of osteoporosis or cause heart problems if you have underlying heart disease.

Talk to your doctor if you have any of the symptoms above or if you feel that you should be taking a different dosage of thyroid hormone.