You may have a very mild form of hyperthyroidism called subclinical hyperthyroidism if your thyroid tests show that:

• Your thyroid-stimulating hormone (TSH) levels are low.
• Your thyroid hormones thyroxine (T4) and triiodothyronine (T3) are normal.

Subclinical hyperthyroidism is different from hyperthyroidism. Your TSH levels are low but your thyroid hormone levels are normal.

If you have subclinical hyperthyroidism, you may have no symptoms at all. Or you may lose weight or feel anxious.

People with subclinical hyperthyroidism may also develop some of the more serious problems related to hyperthyroidism such as heart and bone problems. But experts do not know whether the benefits of treating subclinical hyperthyroidism outweigh the risks. For this reason, if you have subclinical hyperthyroidism, your doctor may just watch you closely.