A novel approach to the treatment of age-related bone loss is demonstrated: "An investigational drug that inhibits serotonin synthesis in the gut, administered orally once daily, effectively cured osteoporosis in mice and rats ... Serotonin in the gut has been shown in recent research to stall bone formation. The finding could lead to new therapies that build new bone; most current drugs for osteoporosis can only prevent the breakdown of old bone. ... Prior to this discovery, serotonin was primarily known as a neurotransmitter acting in the brain. Yet, 95 percent of the body's serotonin is found in the gut, where its major function is to inhibit bone formation (the remaining five percent is in the brain, where it regulates mood, among other critical functions). By turning off the intestine's release of serotonin, the team was able, in this new study, to cure osteoporosis in mice that had undergone menopause. ... [Researchers] administered the compound orally, once daily, at a small dose, for up to six weeks to rodents experiencing post-menopausal osteoporosis. Results demonstrated that osteoporosis was prevented from developing, or when already present, could be fully cured. Of critical importance, levels of serotonin were normal in the brain, which indicated that the compound did not enter the general circulation and was unable to cross the blood-brain barrier, thereby avoiding many potential side effects."