Osteoporosis is rare in children and adolescents and when it does occur, it is usually caused by an underlying medical disorder or by medications used to treat the disorder. This is called secondary osteoporosis - sometimes, however, there is no identifiable cause of osteoporosis in a child and this is known as idiopathic osteoporosis.

Whatever the causes, juvenile osteoporosis can be a significant problem because it occurs during the child's prime bone-building years, children steadily accumulate bone mass, which peaks sometime before age 30 and the greater their peak bone mass, the lower their risk for osteoporosis later in life.

Secondary osteoporosis, which can affect both adults and children, results from another primary disorder or therapy such as juvenile rheumatoid arthritis where the disease process itself can cause osteoporosis.

In such cases the secondary osteoporosis needs to be identified and the primary disorder treated with the lowest effective dose of the osteoporosis-inducing medication.Some studies have found that children with juvenile rheumatoid arthritis have bone mass that is lower than expected, especially near the joints affected by arthritis and in other cases, medication used to treat the primary disorder may reduce bone mass - drugs such as prednisone, used to treat severe cases of juvenile rheumatoid arthritis, negatively affect bone mass also a child with juvenile rheumatoid arthritis may avoid physical activity, which is necessary for building and maintaining bone mass, because it may aggravate his or her condition or cause pain.

If an alternative medication is available and effective, the child's doctor may also consider prescribing it - like all children, those with secondary osteoporosis also need a diet rich in calcium and vitamin D, and as much physical activity as possible given the limitations of the primary disorder.

Other primary disorders, medications, and behaviours which may affect bone mass include

diabetes, osteogenesis imperfecta, hyperthyroidism, hyperparathyroidism, Cushing's syndrome, malabsorption syndromes, anorexia nervosa, kidney disease and medications such as anticonvulsants for epilepsy, corticosteroids for rheumatoid arthritis, asthma, and immunosuppressive agents.

As with adults prolonged inactivity or immobility, inadequate nutrition (especially calcium, vitamin D), excessive exercise leading to amenorrhea (absence of periods), smoking and alcohol abuse are also factors.