Aging is associated with alterations in Ca²⁺ homeostasis, which predisposes elder people to hyperparathyroidism and osteoporosis. Intestinal Ca²⁺ absorption decreases with aging and in particular active transport of Ca²⁺ by the duodenum. In addition, there are age-related changes in renal Ca²⁺ handling. To examine age-related changes in expression of the renal and intestinal epithelial Ca²⁺ channels, control (TRPV5^+/+) and TRPV5 knockout (TRPV5^-/-) mice with the age of 10, 30 and 52 weeks were studied. Aging of TRPV5^+/+ mice resulted in a tendency towards increased renal Ca²⁺ excretion and significantly decreased intestinal Ca²⁺ absorption, which was accompanied by reduced expression of TRPV5 and TRPV6, respectively, despite increased serum 1,25(OH)₂D₃ levels. Similarly, in TRPV5^-/- mice the existing renal Ca²⁺ loss was more pronounced in elder animals, whereas the compensatory intestinal Ca²⁺ absorption and TRPV6 expression declined with aging. In both mice strains, aging resulted in a resistance to 1,25(OH)₂D₃ and diminished renal vitamin D receptor mRNA levels, while serum Ca²⁺ levels remained constant. Furthermore, 52-weeks old TRPV5^-/- mice showed severe hyperparathyroidism, whereas PTH levels in elder TRPV5^+/+ mice remained normal. In 52-weeks old TRPV5^-/- mice, serum osteocalcin levels were increased in accordance with the elevated PTH levels, suggesting an increased bone turnover in these mice. In conclusion, down-regulation of TRPV5 and TRPV6 is likely involved in the impaired Ca²⁺ (re)absorption during aging. Moreover, TRPV5^-/- mice likely develop age-related hyperparathyroidism and osteoporotic characteristics prior to TRPV5^+/+ mice, demonstrating the importance of the epithelial Ca²⁺ channels in Ca²⁺ homeostasis.