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, because 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 have a greater chance of having 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 will probably just watch you closely.