source: Genetics Home Reference - National Library of Medicine
Graves disease is a condition that affects the function of the thyroid, which is a butterfly-shaped gland in the lower neck. The thyroid makes hormones that help regulate a wide variety of critical body functions. For example, thyroid hormones influence growth and development, body temperature, heart rate, menstrual cycles, and weight. In people with Graves disease, the thyroid is overactive and makes more hormones than the body needs. The condition usually appears in mid-adulthood, although it may occur at any age.
Excess thyroid hormones can cause a variety of signs and symptoms. These include nervousness or anxiety, extreme tiredness (fatigue), a rapid and irregular heartbeat, hand tremors, frequent bowel movements or diarrhea, increased sweating and difficulty tolerating hot conditions, trouble sleeping, and weight loss in spite of an increased appetite. Affected women may have menstrual irregularities, such as an unusually light menstrual flow and infrequent periods. Some people with Graves disease develop an enlargement of the thyroid called a goiter. Depending on its size, the enlarged thyroid can cause the neck to look swollen and may interfere with breathing and swallowing.