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.
Iodine is the trigger mechanism that causes excess cells to disappear to complete this normal process of cell death. Without enough iodine, the extra cells that develop during the menstrual cycle due to the hormonal stimulation do not resolve back to the normal breast architecture. These leftover cells build up over repeated cycles and cause the lumps, soreness, and larger lesions of fibrocystic disease.