Objectives: To study the prevalence and possible mechanisms of hypocalcaemia in HIV infection and AIDS.
Subjects: 828 patients with HIV infection or AIDS and 549 controls.
Interventions: Measurements of total serum calcium and albumin levels. Parameters of calcium homeostatis were determined in a subgroup of 21 hypocalcaemic AIDS patients.
Results: Mean serum calcium was 2.34 +/- 0.13 mmol L-1 in the HIV group vs. 2.46 +/- 0.10 mmol L-1 in controls (P < 0.0001). After adjusting for serum albumin, hypocalcaemia was present in 6.5% of the HIV group vs. 1.1% of controls. Mean serum calcium was declining according to CDC groups, and differed significantly from controls in each group. Regression coefficients of cacium vs. albumin were 0.147 amongst HIV-infected patients and 0.106 for controls. In the subgroup of hypocalcaemic patients with AIDS, 10/21 had vitamin D deficiency, six of these with low ionized calcium levels. Low serum PTH was found in 2/21 patients. Magnesium deficiency in 1/21. Of the remaining eight patients, only one had secondary hyperparathyroidism, while the other seven lacked an adequate PTH response, despite low ionized calcium levels in four subjects.
Conclusions: Mean serum calcium concentrations were lower through all CDC stages, irrespective of albumin, resulting in a higher prevalence of hypocalcaemia in HIV-positive patients compared with controls. In a considerable number, this seems to be caused by vitamin D deficiency and potentially a lack of adequate PTH secretion, but further studies are needed to confirm this.