Definition

Factitious hyperthyroidism is higher-than-normal thyroid hormone levels in the blood and symptoms that suggest hyperthyroidism. It occurs from taking too much thyroid hormone medicine.

Hyperthyroidism is also known as overactive thyroid.

Alternative Names

Factitious thyrotoxicosis; Thyrotoxicosis factitia; Thyrotoxicosis medicamentosa; Factitious hyperthyroxinemia

Causes

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.

Hyperthyroidism can also be caused by taking too much thyroid hormone medicine for hypothyroidism. This is called factitious hyperthyroidism. When this occurs because the prescribed dosage of hormone medicine is too high, it is called iatrogenic, or doctor-induced, hyperthyroidism. This is common. Sometimes this is intentional (for some people with depression or thyroid cancer), but often this happens because the dose is not adjusted based on follow-up blood tests.

Factitious hyperthyroidism can also occur when someone takes too much thyroid hormone on purpose and may conceal this. This is very uncommon. These may be people:

• Who have mental disorders such as Munchausen syndrome
• Who are trying to lose weight
• Who are being treated for depression or infertility

Children may take thyroid hormone pills accidentally.

Symptoms

The symptoms of factitious hyperthyroidism are the same as those of hyperthyroidism caused by a thyroid gland disorder, except that:

• There is no goiter. The thyroid gland is often small.
• The eyes do not bulge, as they do in Graves disease (the most common type of hyperthyroidism).
• The skin over the shins does not thicken, as it sometimes does in people who have Graves disease.

Exams and Tests

Blood tests used to diagnose factitious hyperthyroidism include:

• Free T4
• Thyroglobulin
• Total T3
• Total T4
• TSH

Other tests that may be done include radioactive iodine uptake or thyroid ultrasound.

Treatment

Your health care provider will tell you to stop taking thyroid hormone. If you need to take it, your provider will reduce the dosage.

You should be re-checked in 2 to 4 weeks to be sure that the signs and symptoms are gone. This also helps to confirm the diagnosis.

People with Munchausen syndrome will need mental health treatment and follow up.

Outlook (Prognosis)

Factitious hyperthyroidism will resolve on its own when you stop taking or lower the dosage of thyroid hormone.

Possible Complications

When factitious hyperthyroidism lasts a long time, the same complications as untreated or poorly treated hyperthyroidism may develop:

• Abnormal heartbeat (atrial fibrillation)
• Anxiety
• Chest pain (angina)
• Heart attack
• Loss of bone mass (if severe, osteoporosis)
• Weight loss
• Infertility
• Problems sleeping

When to Contact a Medical Professional

Contact your provider if you have symptoms of hyperthyroidism.

Prevention

Thyroid hormone should be taken only by prescription and under the supervision of a provider. Regular blood tests are often needed to help your provider adjust the dose you are taking.

References

Jonklaas J. Hypothyroidism. In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 74.

Pearce EN, Hollenberg AN. Thyroid. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 207.