Extremely high circulating levels of 1 alpha,25-dihydroxyvitamin D3 in the marmoset, a new world monkey

Compared to most mammals, the marmoset, a new world monkey, requires particularly large amounts of vitamin D to maintain normal growth. We compared serum concentrations of vitamin D metabolites in marmosets with rhesus monkeys and humans. The circulating levels of 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] in marmosets were 4 to 10 times higher than those in rhesus monkeys and humans. But none of the marmosets exhibited hypercalcemia. In two marmosets which had suffered bone fractures, the 1 alpha,25(OH)2D3 levels were particularly elevated. These results suggest that the marmoset has an end-organ resistance to 1 alpha,25(OH)2D3.