Like the M 1 and M 3 muscarinic receptor, M 5 receptors are coupled with G proteins of class Gq that upregulate phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signaling pathway.
Radioactive iodine is a very effective type of treatment for cancer of the thyroid gland. Thyroid cells absorb iodine. The radioactive iodine from the drink or capsule is absorbed into your body and picked up by the thyroid cancer cells wherever they are. So it can kill the cancer cells even if they have spread.
A low-iodine diet reduces iodine consumption (on most diets to below 50 micrograms (mcg) of iodine per day (on some diets to below 80-100 mcg per day). The American Thyroid Association recommends that the low-iodine diet include less than 50 mcg of iodine per day.