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.
If you notice these symptoms, call your doctor and ask about having your thyroid tested. Left untreated, an overactive thyroid can cause other health problems, such as an increased risk for osteoporosis and potential heart trouble. The shaking may be subtle, or it could be to the point where you can't steadily carry a drink without spilling it. 2  Diarrhea. 3  An overactive thyroid causes the digestive system to speed up, and this leads to frequent, loose bowel movements. 4  Eye problems.