25-Hydroxycholecalciferol absorption in steatorrhoea and postgastrectomy osteomalacia.

Post-absorption levels of 25-hydroxy vitamin D (25-OHD) after oral administration of 25-hydroxycholecalciferol (25-OHD3) were measured in 11 subjects. Five had presented with steatorrhoea of various causes while six had post-gastrectomy osteomalacia. Post-absorption levels of 25-OHD were low in four of the patients with steatorrhoea but normal in five of those with post-gastrectomy osteomalacia. There was a significant inverse correlation between peak post-absorption 25-OHD levels and faecal fat excretion. All patients with active post-gastrectomy osteomalacia had subnormal baseline plasma 25-OHD levels, which indicates that the condition is due to a deficiency of vitamin D. Only two of the patients with osteomalacia had estimated dietary vitamin D intakes ofer 1-75 microng/day. These findings suggest that an oral 25-OHD absorption test may be a valuable measure of small intestinal function and that poor dietary vitamin D intake rather than impaired absorption of the vitamin may be the major cause of post-gastrectomy osteomalacia.