Typically veins are generally wider than arteries, and therefore the pressure is lower. Capillaries are tiny vessels, so repsent high resistance to the incoming blood, so the rate of blood flow through will be quite low. All blood from the artery eventually passes through capillaries and into the vein.
Graves' disease. Graves' disease is the most common cause of overactive thyroid. It can run in families and can occur at any age, although it is most common in women aged 20-40 years old. You are more likely to develop Graves' disease if you smoke. Graves' disease is an autoimmune condition.
The most common cause of overactive thyroid, according to the American Thyroid Association, is Graves' Disease - an auto-immune disorder that tends to run in families. Growths on the thyroid, called nodules, can spur excess hormone production, as can thyroiditis, overuse of iodine supplements, or regular use of iodine containing medications.