ConditionHormones & metabolism
Toxic Adenoma (Hot Thyroid Nodule)
A toxic adenoma is a single benign lump (nodule) in the thyroid gland that produces thyroid hormone on its own, ignoring the body's normal controls. It causes hyperthyroidism, with symptoms such as a fast heartbeat, weight loss, heat intolerance, tremor and anxiety, and sometimes a visible lump in the neck. On a thyroid scan, it appears as a "hot" nodule. It is almost never cancerous. Treatment with radioactive iodine or surgery is usually curative.
Also called: Hot thyroid nodule, autonomously functioning thyroid nodule, toxic thyroid nodule, Plummer's adenoma, hyperfunctioning thyroid nodule
At a glance
- What it is
- A single, benign, overactive thyroid nodule causing hyperthyroidism.
- Who gets it
- More common in older adults and in iodine-deficient regions; women more than men.
- Symptoms
- Palpitations, weight loss, heat intolerance, anxiety, tremor, sometimes a neck lump.
- Diagnosis
- Low TSH, raised thyroid hormones, ultrasound, and a radioactive iodine uptake scan showing a "hot" nodule.
- Treatment
- Radioactive iodine, surgery to remove the nodule, or long-term antithyroid medicine; radiofrequency ablation in some centers.
- Cancer risk
- Very low.
When to get help
Call 911 or go to the ER
- High fever, a very fast or irregular heartbeat, agitation, confusion, vomiting or diarrhea in someone with hyperthyroidism (possible thyroid storm): call 911 or your local emergency number
- Chest pain, fainting or severe shortness of breath with a racing heart
See a doctor within a day or two
- A new irregular heartbeat or a resting heart rate over 120
- A neck lump causing trouble swallowing or breathing
Book a routine appointment
- Palpitations, weight loss, heat intolerance, sweating or tremor
- A lump in the front of the neck
- Abnormal thyroid blood tests
How a toxic adenoma develops
Normally, the pituitary gland adjusts thyroid hormone production using thyroid-stimulating hormone (TSH). In a toxic adenoma, a genetic change within the nodule's cells, most often in the TSH receptor gene, switches the nodule permanently "on". It keeps making hormone regardless of TSH. As thyroid hormone rises, TSH falls, and the rest of the gland becomes inactive.
Nodules usually need to be about 2.5 to 3 cm or larger before they produce enough hormone to cause symptoms. Smaller autonomous nodules may cause only subclinical hyperthyroidism, with low TSH but normal hormone levels.
Symptoms
Symptoms are those of hyperthyroidism, often milder and slower to develop than in Graves' disease:
- palpitations or a fast heartbeat
- weight loss despite normal or increased appetite
- heat intolerance and sweating
- tremor, nervousness and irritability
- poor sleep and fatigue
- frequent bowel movements
- muscle weakness
- lighter or irregular periods
- a visible or palpable lump in the neck
In older adults, the main signs may be atrial fibrillation, weight loss or fatigue. There are no eye changes, which helps distinguish it from Graves' disease.
Toxic adenoma vs other causes of hyperthyroidism
| Toxic adenoma | Toxic multinodular goiter | Graves' disease | |
|---|---|---|---|
| Thyroid scan | One hot nodule, rest suppressed | Several hot and cold areas | Diffuse, high uptake |
| Typical age | Middle-aged to older | Older | Younger to middle-aged |
| Eye disease | No | No | Possible |
| Antibodies | Negative | Negative | TSH receptor antibodies positive |
| Remission without definitive treatment | Rare | Rare | Possible with medicines |
Diagnosis
- Blood tests: low TSH with high free T4 and/or T3.
- Thyroid ultrasound: shows the nodule's size and features.
- Radioactive iodine uptake and scan: the nodule takes up iodine (hot) while the rest of the gland is suppressed. This confirms autonomy.
- TSH receptor antibodies: negative, helping exclude Graves'.
- Biopsy: usually not needed for hot nodules, because they are rarely cancerous.
Treatment
Radioactive iodine
A capsule or drink of radioactive iodine is taken up mainly by the overactive nodule and destroys it over weeks to months. It is effective in most people. Because the rest of the gland is suppressed, hypothyroidism is less common than after Graves' treatment, but can develop later. It is not used in pregnancy or breastfeeding.
Surgery
Removal of the thyroid lobe containing the nodule (lobectomy) rapidly and reliably cures hyperthyroidism, removes the lump, and leaves the other lobe working. It is preferred for large nodules, pressure symptoms, or when a quick cure is needed.
Medicines
- Antithyroid medicine (methimazole) controls hormone levels but does not cure the nodule; long-term use is an option for people who are not candidates for other treatments.
- Beta-blockers control heart rate and tremor while waiting for definitive treatment.
Ablation
Radiofrequency or other thermal ablation, guided by ultrasound, can shrink the nodule and reduce hormone production in selected people, at specialized centers.
Complications if untreated
- atrial fibrillation and stroke risk
- heart strain and heart failure
- bone loss (osteoporosis), especially in postmenopausal women
- rarely, thyroid storm
Frequently asked questions
What is a toxic adenoma?
A toxic adenoma is a single benign thyroid nodule that produces thyroid hormone independently, causing hyperthyroidism. It shows up as a "hot" nodule on a radioactive iodine scan.
Is a toxic adenoma cancer?
Almost never. Hot, hormone-producing nodules have a very low risk of cancer, which is why biopsy is usually not needed. A doctor may still examine the nodule's features on ultrasound.
What is the treatment for a toxic adenoma?
The main options are radioactive iodine, which destroys the overactive nodule, and surgery to remove the half of the thyroid containing it. Both are usually curative. Antithyroid medicine can control symptoms but does not cure it.
What is the difference between a toxic adenoma and Graves' disease?
A toxic adenoma is a single overactive nodule with the rest of the thyroid suppressed. Graves' disease is an autoimmune condition that makes the whole gland overactive, may affect the eyes, and is detected by specific antibodies.
Sources
This guide was written from current patient and clinical guidance, including:
- American Thyroid Association: Guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis
- American Thyroid Association: Thyroid nodules patient information
- National Institute of Diabetes and Digestive and Kidney Diseases: Hyperthyroidism
- MedlinePlus: Hyperthyroidism
- Endocrine Society: Thyroid nodules