Fat is another significant storage site, while the lungs and kidneys may also be capable of storage. Transport
Until recently, it was thought that the sole important retinoid delivery pathway to tissues involved retinol bound to retinol-binding protein (RBP4). More recent findings, however, indicate that retinoids can be delivered to tissues through multiple overlapping delivery pathways, involving chylomicrons, very low density lipoprotein (VLDL) and low density lipoprotein (LDL), retinoic acid bound to albumin, water-soluble β-glucuronides of retinol and retinoic acid, and provitamin A carotenoids.The range of serum retinol concentrations under normal conditions is 1–3 μmol/L. Elevated amounts of retinyl ester (i.e., >10% of total circulating vitamin A) in the fasting state have been used as markers for chronic hypervitaminosis A in humans. Candidate mechanisms for this increase include decreased hepatic uptake of vitamin A and the leaking of esters into the bloodstream from saturated hepatic stellate cells. Effects
Effects include increased bone turnover and altered metabolism of fat-soluble vitamins. More research is needed to fully elucidate the effects. Increased bone turnover
Retinoic acid suppresses osteoblast activity and stimulates osteoclast formation in vitro, resulting in increased bone resorption and decreased bone formation.
Although not considered part of standard treatment, they might be of some benefit to humans. Vitamin E appears to be an effective treatment in rabbits, and prevents side effects in chicks
Taurine significantly reduces toxic effects in rats. Retinoids can be conjugated by taurine and other substances. Significant amounts of retinotaurine are excreted in the bile, and this retinol conjugate is thought to be an excretory form, as it has little biological activity. Red yeast rice ("cholestin") – significantly reduces toxic effects in rats. Vitamin K prevents hypoprothrombinemia in rats and can sometimes control the increase in plasma/cell ratios of vitamin A. See also
Vitamin poisoning
Far Eastern Party
Retinoic acid syndrome
Piblokto

References
External links

Facts about Vitamin A and Carotenoids, from the National Institutes of Healths Office of Dietary Supplements.