Hey, folks. Thanks for sticking around despite my relative blogopenia. Real life pulls at me relentlessly, and needs must when the Devil drives. But for a few moments, at least, I have some time to myself. PalKid's having a sleepover and is playing some sort of "tsunami magic pony land" game with her friend, and MrsPal is out having coffee with a friend. I figure I have about a half an hour before some sort of fight erupts downstairs, likely having to due with said magic pony land and the oncoming tsunami.
Speaking of tsunamis, I'm pretty much glued to the set, watching the news from the nuclear plants in Japan. There's a lot of talk about "iodine" in this context. Nuclear fission has many toxic products, one of which is iodine-135. It isn't the most dangerous fission product, but it has specific dangers that can be prevented (that is, prevented in ways other than preventing a nuclear disaster in the first place).
The thyroid gland is responsible for the production of thyroid hormone, a chemical that modulates many critical physiologic functions. A key component of this hormone is iodine, an element naturally present in the diet to a greater or lesser extent. Like many hormones, thyroid hormone production is regulated by a feedback loop. When the brain senses a drop in thyroid levels, it sends a chemical signal to the gland to ramp up production. When thyroid levels rise, the brain sends a signal to turn things down.
Iodine is not evenly distributed in the world, and in regions with less iodine in the environment, the thyroid cannot produce enough hormone. The brain senses this, and sends the signal to the gland to ramp up production. The gland responds by growing. And growing.
The results can be quite dramatic, and so can treatment. When iodine is consumed, it collects in the thyroid, so taking in iodine can both prevent and treat goiters. This avidity for iodine is also exploited in the diagnosis and treatment of other thyroid diseases. Radioactive isotopes of iodine can be used, for instance, to image the thyroid gland. A patient can be given a small amount of a radioisotope of iodine and a gamma camera can look for thyroid tissue that "lights up". It can also be used to treat thyroid cancers.
Radioactive iodine is toxic to cells, and since iodine-135 is taken up mainly in the thyroid, and has a relatively short half-life, a patient can be given a dose high enough to kill off a diseased or cancerous thyroid gland. If a thyroid cancer has spread, the iodine will "seek out" metastases and kill them.
Radioactive iodine is used very, very carefully. When I was a medical resident, we would round on I-135 patients from the doorway, and the nutrition service would leave food at the door. I-135 from, say, a nuclear accident can be taken up by the thyroid, causing genetic damage to thyroid cells which lead to cancer. This continues to happen in the areas affected by the Chernobyl disaster.
(Speaking of disaster, someone just yelled, "Pillow fight!" Ten bucks this ends poorly.)
Unlike many other types of radiation poisoning, I-135 poisoning is preventable. People in danger of exposure, especially kids, can be given iodine tablets or liquid. The non-radioactive iodine is taken up quickly by the thyroid, blocking the entrance of radioactive iodine, preventing future cancers. The thyroid can only take so much iodine, and the rest is excreted, radioactive or otherwise.
I imagine that many Japanese children will get unneeded doses of iodine in the next several days. But needs must when the Devil drives.