When people have Thyroid cancer treatment is it only the cancer cells that pick up and are killed by the radioactive Iodine? If so why?

The radioactive iodine kills all the thyroid cells, not just the cancerous ones.

I assume you are talking about radiation therapy (there are several different treatments for thyroid cancer). The answer to your question is it depends on the type of therapy used whether all of the tissue is destroyed or just the cancer cells.

“Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.

Radiation therapy may be given after surgery to kill any thyroid cancer cells that were not removed. Follicular and papillary thyroid cancers are sometimes treated with radioactive iodine (RAI) therapy. Higher doses than the amounts used to diagnose thyroid cancer are used. RAI is taken by mouth and collects in any remaining thyroid tissue, including thyroid cancer cells that have spread to other places in the body. Since only thyroid tissue takes up iodine, the RAI destroys thyroid tissue and thyroid cancer cells without harming other tissue. Before a full treatment dose of RAI is given, a small test-dose is given to see if the tumor takes up the iodine.”

Here is where you can read more about thryroid cancer.

If I recall correctly, the cancer cells are growing at such a great rate that they consume more than the normal amount of iodine. The amount they take is hazardous, but the amount a healthy cell takes would not kill it.

Or I am wrong.

@jackm I think it’s the other way around. I’m at work and pulled up an article on radioiodine treatment for thyroid cancer and here’s the applicable slightly edited for clarity statement.

Thyroid tissue has a unique ability to take up iodine from blood. Like iodine, radioiodine is taken up and concentrated in thyroid follicular cells because they have a membrane sodium-iodide transporter. Compared with normal thyroid follicular cells, thyroid cancer cells have reduced expression of the transporter, which may account for the low 131-I uptake in thyroid cancer tissue. 131-I causes acute thyroid-cell death… 131-I…is of no value in patients whose thyroid cancers do not concentrate iodide.