Factitious hyperthyroidism is when your body has too much thyroid hormone, caused by taking too much thyroid hormone medication.

The thyroid gland produces the hormones thyroxine (T4) and triiodothyronine (T3). In most cases of hyperthyroidism, the thyroid gland itself is producing too much these hormones.

However, you can also get hyperthyroidism by taking too much thyroid hormone medication. This is called factitious hyperthyroidism. Thyroid hormone medication has been available since 1891 and is used to treat hypothyroidism. Factitious hyperthyroidism may occur when thyroid hormone is prescribed to treat hypothyroidism and the prescribed dose is too high.

It can also occur when a person intentionally takes too much thyroid hormone. People with psychiatric disorders such as Munchausen syndrome deliberately (and usually secretively) take these hormones.

Patients attempting to lose weight and seeking to receive fraudulent insurance compensation also sometimes misuse thyroid hormone. Children may occasionally require treatment for accidental ingestion of thyroid hormone pills.

In rare cases, factitious hyperthyroidism has been found to be caused by eating meat contaminated with thyroid gland tissue.

The symptoms of factitious hyperthyroidism are identical to the symptoms of hyperthyroidism caused by the thyroid gland, with the following exceptions:

• There is no goiter. The thyroid gland is usually small.
• The eyes do not protrude, as they do in Graves' disease (the most common type of hyperthyroidism).
• The skin over the shins does not thicken, as it occasionally does with Graves' disease.

The following test results may indicate hyperthyroidism:

• TSH -- low
• Total T4 -- high
• Free T4 -- high
• Total T3 -- high
• Thyroglobulin -- low
• Radioactive iodine uptake -- low

The patient would have to stop taking thyroid hormone, or if it is medically necessary, the dose must be reduced.

The patient would be re-evaluated in 2 to 4 weeks to be sure that signs and symptoms of hyperthyroidism are gone. This also helps to confirm the diagnosis.

Factitious hyperthyroidism will clear up on its own when thyroid hormone is stopped or the prescribed dose is lowered.

If factitious hyperthyroidism is long-standing, patients are at risk for the same complications as those of untreated or improperly treated hyperthyroidism caused by the thyroid gland.

These complications include the following:

• Irregular heart rhythm
• Atrial fibrillation
• Chest pain (angina)
• Heart attack
• Loss of bone mass (if severe, osteoporosis)
• Weight loss

See the article on hyperthyroidism for more information.

Contact your health care provider if symptoms of hyperthyroidism occur.

Thyroid hormone should be taken only by prescription and under the supervision of a licensed physician.