Familial hypocalciuric hypercalcaemia. II. Intestinal calcium absorption and vitamin D metabolism.

We compared intestinal calcium absorption, measured by a single isotope technique, and serum concentrations of vitamin D metabolites in ten patients with familial hypocalciuric hypercalcaemia (FHH) and ten age- and sex-matched healthy controls. Our results showed no significant differences in intestinal calcium absorption or in serum concentrations of vitamin D metabolites. There was a significant correlation between serum concentrations of PTH, measured with one of our assays, and 1,25(OH)2D. We conclude that neither increased intestinal calcium absorption nor altered vitamin D metabolism plays a part in the hypercalcaemia of FHH.