Graves' disease is an autoimmune disease that causes the thyroid to make too much thyroid hormone. This is known as hyperthyroidism. This makes bodily functions like the heart rate and metabolism speed up.
Sometimes tissue behind the eyes are inflamed and swollen. Skin on the shins and on top of the feet can become rough and thickened.
"Both men and women can get Graves' disease. But it affects women 10 times more often than men. Graves' disease occurs in people of all ages, but most often starts in the 20s and 30s. People who get Graves' disease often have family members who have thyroid or other autoimmune diseases."
It's not known what causes someone to get Graves' disease. It is speculated that some contributing elements may be gender, stress levels, pregnancy, infection or genetic factors.
Vitiligo, rheumatoid arthritis, Addison's disease, type 1 diabetes, pernicious amnesia and lupus are other autoimmune diseases which often develop in people who have Graves' disease.
http://www.medicinenet.com/graves_disease/article.htm