EC ORTHOPAEDICS Short Communication Ionized and Total Calcium, and the Secondary Hyperparathyroidism in Patients with Hypovitaminosis D

Purpose: In this retrospective study we tried to outline the relationship between the ionized calcium (iCa) and secondary hyperparathyroidism (SHPTH) in patients with hypovitaminosis D. Methods: The records of 101 outpatients patients with hypovitaminosis D (25(OH)D < 30 ng /ml) who were also assayed for ionized calcium (iCa), total calcium (tCa) and PTH are presented. They were divided into two groups according to the level of their i Ca; subnormal iCa (G1) and another with normal levels (G2). Results: 26 (25.5%) had i Ca < 1.16 mmol/l (G1) and 75 with normal levels (1.16 1.32 mmol/l) (G2), p = 0.0001. The age was not different in the two groups. The mean of iCa in G1 was significantly lower to that in G2 (1.10 +/0.11 vs. 1.23 +/0.12 mmol/l)respectively, p = 0.0001. The tCa was within normal values (eucalcemic range) in both groups respectively, yet 2 significantly lower in G1, (9.43 +/0.45, range 8.9 10.4 mg/dL vs.9.80 +/ -0.43, range 8.88 11.1 mg/dL) p = 0.0004. None a single case of hypocalcemia was identified. However, the mean of 25 (OH) D in both groups was not different. The R value was weakly positive in the correlation between the iCa and t Ca in both groups. The mean PTH was higher in G1, p = 0.007. 20 patients (20%) expressed secondary hyperparathyroidism (10 in each group, p = 0.009 with levels of 90.6 +/35.1 vs. 83.8 +/13.9 pg/ml respectively, p = 0.75). The R value was positive (0.2867) between the patients with subnormal iCa and SHPTH. Conclusion: Subnormal ionized calcium exhibited higher degree of association/correlation with secondary hyperparathyroidism due to hypovitaminosis D than that of the total calcium. Ionized calcium to a great extent can be considered as the major stimulator of the PTH. Estimating it therefore should be considered essential in future studies addressing similar or other pertinent issues.