Parathyroid hormone (PTH) and vitamin D status (25-hydroxyvitamin D (25(OH)D)) were assessed at different ICUs (medical, cardiac surgery, mixed surgical and neurological) in 404 patients (age 63 ± 16 years, 65% male) from September 2008 until November 2009.
The mean serum 25(OH)D level was 19.6 ± 11.2 ng/ml. Normal 25(OH)D levels (>30 ng/ml) were found in 12.4% of all patients. The majority (58.2%) were vitamin D deficient (<20 ng/ml), while 29.4% were considered vitamin D insufficient (>20 and <30 ng/ml) by current definitions. Significant variations of vitamin D levels occurred depending on season, with highest values found in August (27.1 ± 13.1 ng/ml) and the lowest in March (12.5 ± 4.6 ng/ml), respectively. Secondary hyperparathyroidism (PTH >65 pg/ml) was highly prevalent in medical and cardiac surgery patients (43.7% and 37.9%). In an age, sex and SAPS II score adjusted Cox-proportional hazards regression analysis model, patients with low PTH or serum calcium levels, as well as low 25(OH)D levels (cut-off 12 ng/ml) were all at significantly greater risk for all-cause mortality. With all variables included into one model (n = 268 patients) serum calcium remained an independent predictor of mortality, whereas PTH log (P = 0.08) and 25(OH)D (P = 0.16) levels suggested a trend.
Vitamin D deficiency is often encountered in critically ill patients. Higher than the currently recommended daily dose of 200 IU vitamin D3 is probably required for achieving or maintaining normal 25(OH)D levels. Results of this study suggest that baseline parameters reflecting calcium/PTH status are associated with mortality. Whether a disturbance in calcium/vitamin D3 or PTH metabolism develops secondary to the medical condition of ICU patients or is a primary cause of mortality remains to be clarified in prospective analyses.