Factitious hyperthyroidism is the presence of excessive thyroid hormone levels, 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 produces too much of these hormones.

However, hyperthyroidism can also be caused by taking too much thyroid hormone medication for hypothyroidism. This is called factitious hyperthyroidism. When this occurs because the prescribed dose of hormone medication is too high, it is called iatrogenic, or "doctor-induced," hyperthyroidism.

Factitious hyperthyroidism can also occur when a patient intentionally takes too much thyroid hormone. People with psychiatric disorders such as Munchausen syndrome, people attempting to lose weight and those seeking fraudulent insurance compensation sometimes misuse thyroid hormone. Children occasionally ingest thyroid hormone pills accidentally.

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 people with Graves' disease.

The following test results may indicate factitious hyperthyroidism:

• Low levels of TSH
• High levels of total T4
• High levels of free T4
• High levels of total T3
• Low levels of thyroglobulin
• Low radioactive iodine uptake

The patient must stop taking thyroid hormone. If it is medically necessary, the dose must be reduced.

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

Psychiatric consultation and followup is essential for persons with Munchausen syndrome.

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

When factitious hyperthyroidism lasts a long time, patients are at risk for the same complications that occur with untreated or improperly treated hyperthyroidism caused by the thyroid gland.These complications include:

• 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 you experience any of the symptoms of hyperthyroidism.

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