Others have pursued a more conventional pathophysiologic tack to this phenomenon, reasoning that post-menopausal women develop osteoporosis and are estrogen deficient, therefore estrogen replacement would be the appropriate treatment for osteoporosis.43 We, on the other hand, have tested the hypothesis that microgravity would inhibit PTHrP expression in bone and lung cells. This evidence concerns the gene PTHLH and osteoporosis.