The skeleton is made up of bones, which provide support and shape to the body. They protect soft internal organs, such as the brain, and heart, from injury. Together with muscles, strong bones enable the body to move freely. Bones have a solid outer surface, called compact bone. The inner bone is called spongy bone, because it is less dense than compact bone, and has many small holes like a sponge. Bones contain cells called osteoclasts that break down bone tissue. Other cells, called osteoblasts, make new bone tissue using minerals, such as calcium and phosphate, from the blood. Hormones, such as estrogen, growth hormone, and testosterone, help keep the number and activity of osteoblasts higher than osteoclasts so that more bone is made than removed. Physical forces and pressure during exercise also help bones to grow stronger and denser. These processes allow bones to grow strong in children and young adults. People have their strongest, most dense bones, called peak bone mass, in their thirties. After this age, osteoclasts gradually remove more bone than the osteoblasts make. Osteoporosis is a condition that leads to weakened bones, causing them to break more easily. Healthy bone is dense enough to support and protect the body, and to handle the stresses of movement and minor injuries. However, people with osteoporosis have abnormally thin bones with larger holes in the spongy bone. There are two types of osteoporosis. Primary osteoporosis is usually related to older age, as well as a reduced amount of estrogen in women. Secondary osteoporosis affects both children and adults. It is related to other diseases or conditions, such as cancer, hormone problems, or use of certain medications. A person has a greater risk for either type of osteoporosis if they don’t develop enough bone mass when they are growing from childhood to adulthood. Risk factors that can lead to low peak bone mass include: a family history of osteoporosis, being white or Asian, being female, a poor diet, certain medications, such as steroids or certain seizure medicines, lack of physical activity and weight-bearing exercise, and lifestyle behaviors, such as smoking and drinking too much alcohol. A person also has a greater risk for either type of osteoporosis if they have an abnormal amount of bone loss after age thirty. Some bone loss is normal after this age. However, a person with the same risk factors for low peak bone mass can be more likely to get osteoporosis as they age. Increased bone loss is also common in women after the time of a woman’s last period, called menopause. After menopause, a woman’s ovaries stop making the hormone estrogen. With the drop in hormones, bone-removing cells, called osteoclasts, are more active than the bone-making cells, called osteoblasts. Bones may break, or fracture, easily because they are unable to withstand the physical strain and pressure from even normal activities. Common fracture locations in people with osteoporosis include the wrists, spine, and hips. Building strong, healthy bones through a diet rich in calcium and vitamins, and getting regular exercise, can help prevent as well as treat osteoporosis. Common medications for osteoporosis include: biophosphonates, a medication called Denosumab, selective estrogen receptor modulators, or SERMS, and calcitonin. In general, these medications act on bone-removing cells, called osteoclasts. Parathyroid hormone acts on bone-making cells, called osteoblasts. Food or supplements containing calcium and vitamin D are also recommended for osteoporosis. For more information, talk to a health care professional.