The thyroid gland is a small butterfly-shaped
structure located in the front of the neck. Hypothyroidism (low thyroid function) occurs when the thyroid gland does not produce
enough of a substance called thyroid hormone, which
helps to regulate the body's metabolism. Hypothyroidism develops in about
5% of the population in the United States and is especially common in women
older than 60 years. The December 10, 2003, issue of JAMA includes an article about treating hypothyroidism.