What happens to an astronaut's bones when they are in space?

In space, astronauts experience microgravity, which leads to a decrease in bone density due to reduced mechanical stress on the skeletal system. This phenomenon is known as spaceflight osteopenia, where bones lose calcium and other minerals, making them weaker and more susceptible to fractures. Research indicates that astronauts can lose about 1% to 2% of their bone mass per month while in space. To mitigate this effect, astronauts engage in regular strength and resistance training during their missions.