The calcium balance is tightly maintained by efficient feedback mechanisms involving parathyroid glands, bone, intestine and kidney. Changes in ionized calcium concentration are detected by the calcium-sensing receptor (CaSR) present in parathyroid cells, which subsequently modulates the parathyroid hormone (PTH) secretion. PTH in turn participates in the maintenance of plasma calcium levels within the physiological range by modulating bone resorption, renal calcium reabsorption and indirectly, by increasing the 1,25-dihydroxyvitamin D3 synthesis to regulate intestinal absorption of calcium. Importantly, genetic studies as well as molecular cloning strategies recently identified new epithelial ion channels as the gatekeepers of active calcium absorption processes. These channels are members of the transient receptor potential (TRP) superfamily. TRPV5 and TRPV6 are responsible for the rate-limiting calcium entry in kidney and intestine, respectively [2,3]. Dysregulation or malfunction of these influx pathways has been associated with renal wasting and intestinal malabsorption of calcium. Ageing is tightly associated with a negative calcium balance leading to among others osteoporosis, arteriosclerosis and ectopic calcification. Recently, klotho was identified as the new ‘anti-aging’ hormone being instrumental in the process of age-related adaptations in the calcium balance. Klotho is a type I membrane glycoprotein which shares homology to β-glucosidase enzymes. Interestingly, klotho gene ablation resulted in a syndrome closely resembling human ageing, including short life span, bone aberrations, skin atrophy and a disturbed calcium balance together with high serum vitamin D levels. Recently, we showed that klotho is predominantly expressed in kidney, where it is secreted in serum and urine. Furthermore, we demonstrated that TRPV5 and TRPV6 are stimulated by klotho via a novel extracellular activation mechanism [1]. We demonstrated that klotho hydrolyses via its β-glucuronidase activity the extracellular TRP channel sugar residues, entrapping the channel protein in the plasma membrane to maintain durable calcium transport activity. Channel regulation by extracellular modification of the protein glycan is a novel activation mechanism and might be applicable to other membrane proteins as well. The activity of TRPV5 and TRPV6 is controlled at the transcriptional and translational level by hormones and dietary content of divalents as studied in various animal models. Besides this long-term control, the epithelial channels can be regulated by trafficking to and from the plasma membrane and by direct activation at the plasma membrane as investigated in several cell models. The recent elucidation of channel-associated proteins has provided new molecular mechanisms underlying these processes. Our recently performed studies combined electrophysiological, biochemical, molecular biological and confocal fluorescent imaging techniques and should ultimately allow the establishment of a comprehensive cellular model of calcium (re)absorption.