1; AP alkaline phosphatase; Al aluminium ions; BMD bone mineral density; BSO dl-buthionine-(S; CB calbindin; CPP caseinophosphopeptides; ER oestrogen receptor; FCA fractional Ca absorption; FGF-23 fibroblast growth factor-23; GC glucocorticoid; GSH glutathione; IGF-1 insulin-like growth factor-1; KO knockout; MEL melatonin; MEN menadione; NCX1 intestinal Na+/Ca2+ exchanger; NaDOC sodium deoxycholate; OVX ovariectomised; PMCA plasma membrane Ca2+ ATPase; PTH parathyroid hormone; TRP transient receptor potential; TRPV transient receptor potential vanilloid; UDCA ursodeoxycholic acid; VDD vitamin D deficiency; VDR vitamin D receptor; 25(OH)2D3 1; 25-dihydroxycholecalciferol; Hormonal effects; Intestinal calcium absorption; Nutritional factors; R)-sulfoximine; Transcellular and paracellular pathways