You may have hyperthyroidism if you:

• Feel nervous, moody, weak, or tired.
• Have hand tremors, or have a fast or irregular heartbeat, or have trouble breathing even when you are resting.
• Feel very hot, sweat a lot, or have warm, red skin that may be itchy.
• Have frequent and sometimes loose bowel movements.
• Have fine, soft hair that is falling out.
• Lose weight even though you are eating normally or more than usual.

Also, some women have irregular menstrual cycles or stop having periods altogether. And some men may develop enlarged breasts.

The symptoms of hyperthyroidism are not the same for everyone. Your symptoms will depend on how much hormone your thyroid gland is making, how long you have had the condition, and your age. If you are older, it's easy to mistakenly dismiss your symptoms as normal signs of aging.

Specific symptoms of Graves' disease

People with Graves' disease often have additional symptoms, including:

• Goiter , which is an enlarged, painless thyroid gland.
• Thickened nails that lift off the nail beds.
• Pretibial myxedema, which is lumpy, reddish, thick skin on the front of the shins and sometimes on top of the feet.
• Clubbing (fingers with wide tips).
• Graves' ophthalmopathy, which causes bulging, reddened eyes , among other symptoms.

Complications

Graves' ophthalmopathy is a possible complication of hyperthyroidism. It can occur before, after, or at the same time as your symptoms of hyperthyroidism. People with Graves' ophthalmopathy develop eye problems, including bulging, reddened eyes , sensitivity to light, and blurring or double vision. People who smoke are more likely to develop Graves' ophthalmopathy.

If you have Graves' ophthalmopathy, it may temporarily get worse if you have radioactive iodine treatment. On the other hand, it may get better if you take antithyroid medicine.

If you do not treat your hyperthyroidism, you may:

• Lose weight because your body's metabolism is faster.
• Have heart problems such as rapid heart rate, atrial fibrillation, and heart failure.
• Have trouble replacing calcium and other minerals in your bones, which can lead to osteoporosis.

In rare cases, hyperthyroidism can cause a life-threatening condition called thyroid storm, which happens when the thyroid gland releases large amounts of thyroid hormones in a short period of time.