What it means
On a thyroid scan, working thyroid tissue takes up a small amount of radioactive iodine or technetium. A hot nodule takes up more tracer than the surrounding gland, so it is actively making thyroid hormone, often without the body's usual control. A cold nodule takes up less than the tissue around it. A nodule with about the same uptake may be called warm. Hot and cold describe tracer uptake, not temperature or danger.
When it matters
Hot nodules are almost always benign and rarely need a needle sample. Some make too much hormone and cause an overactive thyroid. A report may call this a toxic adenoma, where toxic means excess hormone, not cancer. Most cold nodules are benign too, such as cysts or harmless growths, but cancer is more likely in a cold nodule than a hot one. So cold nodules are usually checked with ultrasound, and a fine-needle sample may follow.
Questions to ask your doctor
- Is my nodule hot, warm or cold, and how big is it on ultrasound?
- Could a hot nodule explain my thyroid blood test results?
- Does a cold nodule mean I need a needle biopsy?
Read more: Thyroid Uptake Scan: What Hot and Cold Nodules Mean
