KL (klotho) is a multifunctional protein that serves as both a membrane-bound receptor and circulating hormone involved in aging regulation and metabolic processes. The protein exists in three forms: full-length transmembrane, truncated soluble, and secreted α-Klotho, each with potentially different functions 1. KL functions as an aging-suppressor gene, with overexpression extending lifespan in mice while mutations shorten it 1. The protein regulates phosphate, calcium, and vitamin D metabolism and may function as an anti-aging hormone by inhibiting insulin/IGF1 signaling pathways 1. KL suppresses insulin and Wnt signaling pathways, inhibits oxidative stress, and regulates phosphatase and calcium absorption 1. In respiratory diseases, KL deficiency contributes to chr13 obstructive pulmonary disease (COPD) pathogenesis by regulating club cell senescence and differentiation, with reduced KL expression associated with increased age-related markers and pulmonary inflammation 2. Point mutations in the human KL gene are associated with hypertension and kidney disease, suggesting its essential role in maintaining normal renal function 1. The protein's role in aging regulation and metabolic homeostasis makes it clinically significant for understanding age-related diseases and potential therapeutic interventions.