When the thyroid produces too much hormone, the body uses energy faster than it should. This condition is called hyperthyroidism. When the thyroid doesn't produce enough hormone, the body uses energy slower than it should. This condition is called hypothyroidism. There are many different reasons why either of these conditions might develop.
In hyperthyroidism, the thyroid gland is overactive. It produces too much of its hormone. Hyperthyroidism affects about 1 percent of women. It’s less common in men.
Graves’ disease is the most common cause of hyperthyroidism, affecting about 70 percent of people with an overactive thyroid. Nodules on the thyroid — a condition called toxic nodular goiter or multinodular goiter — can also cause the gland to overproduce its hormones.
- Irritability/nervousness
- Muscle weakness/tremors
- Infrequent, scant menstrual periods
- Weight loss
- Sleep disturbances
- Enlarged thyroid gland
- Vision problems or eye irritation
- Heat sensitivity
Hypothyroidism is the opposite of hyperthyroidism. The thyroid gland is underactive, and it can’t produce enough of its hormones.
Hypothyroidism is often caused by Hashimoto’s disease, surgery to remove the thyroid gland, or damage from radiation treatment. In the United States, it affects around 4.6 percent of people 12 years old and older. Most cases of hypothyroidism are mild.
- Fatigue
- Frequent, heavy menstrual periods
- Forgetfulness
- Weight gain
- Dry, coarse skin and hair
- Hoarse voice
- Intolerance to cold