What are the causes of osteopenia?

Osteopenia is defined as a decrease in bone density caused by reduced bone formation and/ or increased bone resorption.

Reduction in bone formation may result from either inadequate matrix formation or inadequate the matrix calcification.

Significant failure of bone mineralization, or osteopenia, occurs in more than 50% of premature infants weighing less than 1000g at birth.

Replacement of bone matrix by benign or malignant bone proliferation (e.g. thalassemia, multiple myeloma and leukemia) or bone marrow disease (e.g. metastases, infections and storage disease) may also result in osteopenia.

Deficiency of calcium and phosphorus are the principal causes. Demands for rapid growth in the third trimester are met by intrauterine mineral rates of approximately 120 mg of calcium and 60 mg of phosphorus/kg/day.

Poor mineral intake and absorption after birth in undermineralized new and remodeled bone.

Other most common cause of osteopenia may be advanced patent age or stress-shielding can occur. 

Smoking, poor calcium intake, immobilization, malnutrition, a hypogonadal state, and family history are all risk factors for osteopenia.
What are the causes of osteopenia?