The thyroid gland produces hormones that have various effects on the body. These hormones are called T3 and T4 for short, but T3 is the more actively available form and T4 is turned into T3 where necessary. At a normal level of production, the thyroid hormones help regulate many of the body's metabolic activities. Examples of thyroid-influenced processes include beneficial effects on bone turnover, movement of food through the digestive tract, the ability of the muscles to contract and control of breathing pattern and heart rate. Due to these varied effects, when too much thyroid hormone is produced, the affected person can suffer a wide variety of symptoms. Hyperthyroidism, or a high thyroid, may also be known as an overactive thyroid or thyrotoxicosis.
Weight loss is a common symptom of high thyroid hormone levels, even though the affected person generally has an increased or normal appetite. On the other hand, an increased appetite can actually cause weight gain, especially in young people. The increase in appetite is due to an increase in energy use by the body that is triggered by excess thyroid hormone. This excessive energy burning also makes the body warmer than usual, making many people with an overactive thyroid less tolerant of hot environments. A tremor can also be present, which is an inability to keep the muscles still. Some people suffer from palpitations, which describes being aware of your heartbeat, and a faster than normal heart rate is also common. Sweating is another possible symptom.
An overactive thyroid can trigger the digestive system to become more active than usual. This means that food and water run through the body more rapidly, producing symptoms such as excessive bowel movements and more trips to the toilet to urinate. Feeling more thirsty than usual or experiencing diarrhea or vomiting are also possible symptoms, and on rare occasions, stomach pain is a symptom. Some people find they have trouble swallowing, and this is associated with the presence of a goiter, the swelling in the neck due to the thyroid gland enlarging.
Abnormally high thyroid hormone levels can make the affected person less emotionally stable than usual and more likely to feel anxious. The person may also become hyperactive as a result of the disease. Irritability is another possible symptom, as is an inability to concentrate or being unable to sleep normally.
Excessive thyroid hormone tends to produce muscle weakness, especially in the strong muscles in the thighs and upper arms. These are the muscles that are most powerful in getting up out of a chair or in lifting the arms over the head. Another common symptom is excessive tiredness.
Differences in Men and Women
Some men with high thyroid levels may experience erectile dysfunction or breast enlargement. Women may find that their periods become lighter than normal or disappear altogether, which can have adversely affect fertility.
Many people with high thyroid activity have Graves disease. This type of hyperthyroidism is due to antibodies mistakenly attaching to the thyroid and signaling to the gland to produce more hormone than usual. According to "Kumar & Clark's Clinical Medicine," people with hyperthyroidism of the Graves disease variety can have eye problems such as bulging eyes or weakness of eye movement. Of course, the general hyperthyroidism symptoms may also be present.