In older populations, evidence from the SarcoPhAge cohort of community-dwelling older adults indicated that VMR correlates more strongly with PTH levels than either 25(OH)D or 24,25(OH)2D alone, and that low VMR (defined as <4%) was associated with the highest all-cause mortality risk, supporting its value as a functional marker of vitamin D deficiency (11). The gene discussed is PTH; the disease is vitamin D deficiency.