Parathyroid hormone (PTH) acts as an anabolic agent and is used for the treatment for osteoporosis. Daily or once-weekly self-administered subcutaneous injection of human PTH(1-34) (teriparatide) increased bone mineral density (BMD) compared to a placebo in post-menopausal osteoporotic patients. Recently, data have accumulated that collagen cross-link formation in bone affect bone strength. In fact, impaired enzymatic cross-linking and/or an increase in non-enzymatic cross-links, pentosidine, which is a surrogate marker of advanced glycation end products(AGEs), in bone collagen have been proposed as a major cause of bone fragility in osteoporosis. Teriparatide improves bone collagen cross-link formation, microarchitecture, and bone mass, resulting in the increase of bone strength.