Explain the Absorption, Storage and Elimination of thiamin?

After a meal, thiamin is found in the intestine in the free form. Its absorption involves two mechanisms- both active and passive. At lower Intraluminal concentrations (of <1-2mmol/L) thiamin is absorbed by an active sodium-dependent carrier-mediated system. This mechanism involves phosphorylation. At a higher concentration, passive diffusion occurs thiamin is absorbed primarily from the upper jejunum by diffusion and by an active transport mechanism but can also occur in the duodenum and ileum.

After absorption, only a small part passes into circulation as free thiamin while a  greater part is converted into thiamin pyrophosphate (TBP) in the liver and intestinal  rnucosa with the help of the enzyme thiamin  kinase and AT?. A small quantity of thiamin is also converled into thiamin triphosphate (TTP). Thiamin is transported in blood by facilitated diffusion - in erythrocytes in both free and phosphorylated forms and in plasma as free thiamin and TMP. Thiamin or its phosphorylated derivatives are present in negligible amounts in various tissues. Thiamin is excreted in urine.