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.
Full Removal. If your doctor removes your entire thyroid, your body will begin to exhibit symptoms similar to hypothyroidism, due to the lack of thyroid hormones in your body. These symptoms may include fatigue, elevated cholesterol levels, uncontrollable weight gain, muscle weakness and depression.
And health problems may develop as the disease continues. If untreated, hypothyroidism may lead to: 1  Myxedema, a condition that causes swelling of tissues, increased fluid around the heart and lungs, slowed muscle reflexes, and a slowed ability to think.2  Myxedema coma, a rare, life-threatening condition.ut about 1 out of 10 people who have mild hypothyroidism will go on to have hypothyroidism within 3 years. If your thyroid gland has been removed during surgery, hypothyroidism will occur within a few weeks. If you have been treated with radioactive iodine therapy, hypothyroidism may develop within a year.