Q. My mother has been feeling tired, gaining weight and losing hair. Recently she was diagnosed with Hashimoto's thyroiditis. Can you explain what this is, why she has it and what she can do about it?

A. Your mother has an autoimmune disorder; the cells of her own immune system are attacking her thyroid gland.

The function of your thyroid gland, which is in your neck, is to release key hormones and help maintain your body's metabolism. Hashimoto's thyroiditis can damage the thyroid gland and cause low thyroid function, also known as hypothyroidism.

Your mother is not alone. Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States and 5 to 10 times more prevalent in women than men. The condition has a genetic component and tends to recur in families. It has also been linked with other autoimmune disorders, such as celiac disease and type 1 diabetes.

What causes Hashimoto's thyroiditis? It appears that a "trigger" often turns on genes that cause the body to create immune cells to attack the thyroid gland. This trigger can be any number of things.

Factors frequently associated with the onset of Hashimoto's thyroiditis include estrogen surges (such as in pregnancy), insulin surges (common in people with blood sugar imbalances), excessive iodine consumption, high levels of heavy metals (such as mercury), gluten intolerance and excessive stress.

To evaluate for low thyroid function, typically only thyroid stimulating hormone, or TSH, is tested. However, to specifically assess for Hashimoto's thyroiditis, I recommend a blood test to check for thyroid antibodies. This is because a person can have Hashimoto's thyroiditis for a long time before the thyroid gland has sustained enough damage from antibodies to show hypothyroidism (or high TSH). And while the thyroid gland is being damaged by the immune system, one can experience many symptoms associated with low thyroid function, including fatigue, weight gain, dry skin, depression, hair loss, constipation, muscle cramps, increased cholesterol and cold intolerance.

Women with the condition can also have infertility and irregular or heavy periods.

Paradoxically, some people may also experience mild to severe symptoms of excessive thyroid function when the immune system is attacking the thyroid gland. These can include anxiety, weight loss, increased sweating and rapid heartbeat.

Naturopathic doctors treat Hashimoto's thyroiditis as early as possible to prevent further thyroid damage.

We use a comprehensive approach to modulate the immune system and support thyroid function, including herbal medicines, dietary changes to prevent high and low blood sugar, removal of food allergens, heavy-metal detoxification, avoidance of iodine, nutritional supplementation including selenium (200 micrograms daily), and in some cases thyroid hormone support.

Laurie Steelsmith is a naturopathic physician and licensed acupuncturist in Honolulu, as well as author of the new book "Natural Choices for Women's Health," published by Random House. Reach her and read her past columns at www.DrSteelsmith.com. This column is for information only. Consult your health provider for medical advice.