Aim: The aim of this study was to test the hypothesis that Vitamin D deficiency is associated with abnormal Calcium and PTH levels.
Methods: Vitamin D requests at a tertiary hospital in South Africa over 2 years were retrospectively analysed along with calcium and PTH levels.
Results: Only when 25(OH)D level dropped below 25nmol/l, was there a significant rise in PTH. A subnormal 25(OH)D level was also not always related to hypocalcaemia as more than half of patients with their 25(OH)D level below 25nmol/l had calcium levels in the reference range. However, all patients with calcium levels below 1.8mmol/l were shown to have Vitamin D insufficiency.
Conclusion: Hypovitaminosis D may co-exist with a blunted PTH response. Therefore, assumptions about vitamin D status should not be made based on PTH and calcium values. 25(OH)D measurements should be requested when vitamin D deficiency is clinically suspected, irrespective of biochemical results.