Second, α-Klotho is a multifunctional protein similar to a hormone, and regulates the metabolism of phosphates, calcium, and vitamin D. Consistent with this hormone-like role, Klotho mice develop aging phenotypes such as emphysema and osteoporosis in tissues, such as lung and bone, in which the Klotho protein is not expressed14. Here, KL is linked to pulmonary emphysema.