In particular, testosterone levels, dehydroepiandrosterone (DHEA), insulin-like growth factor-1 (IGF-1), hyperparathyroidism, adiponectin, leptin, and vitamin D deficiency were associated with both frailty constructs, whereas insulin-like growth factor binding protein 1–3 (IGFBP 1–3) was related to the deficit accumulation model of Rockwood [53,55,56]. The gene discussed is IGFBP1; the disease is vitamin D deficiency.