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.
There are two fairly common causes of underactive thyroid. 1  The first is a result of previous (or currently ongoing) inflammation of the thyroid gland. Which leaves a large percentage of dead cells of the thyroid due to damage. 2  The second major cause is the broad category of medical treatments.