Endocrine Abstracts

Background: The results of studies evaluating the relationship between serum 25-hydroxyvitamin D (25OHD) with intact PTH (iPTH), calcium (Ca) and phosphorus (P) levels are controversial.

Objective: To determine the diagnostic values of iPTH, Ca and P for the prediction of vitamin D deficiency.

Methods: We analysed iPTH, Ca and P levels in otherwise healthy 700 subjects (619 (88.4%) female, 81 (11.6%) male, mean age 47.44±16.58 years). To define deficiency status, 25OHD were further classified into four groups, (<25 nmol/l as severely deficient, 25–49.9 nmol/l as deficient, 50–74.9 nmol/l as insufficient and ≥75 nmol/l as sufficient, respectively).

Results: The mean 25OHD, iPTH, Ca and P levels were 39.42±29.43 nmol/l, 66.16±34.57 pg/ml, 9.63±0.46 and 3.35±0.52 mg/dl respectively. 271 (38.7%) of the subjects were classified as severely 25OHD deficient, 237 (33.9%) as deficient, 91 (13.0%) as insufficient and 101 (14.4%) as sufficient respectively. iPTH were inversely correlated with 25OHD (r=− 0.264), while no correlation was found between Ca, P, age and gender with 25OHD (r=0.099; r=0.065; r=0.003 and r=0.012 respectively). Secondary hyperparathyroidism (sPTH) were present in 277 (46.24%) of the subjects with low 25OHD levels (in 167 (61.6%), 81 (34.2%) and 29 (31.9%) of the subjects with severely deficient, deficient and insufficient 25OHD levels respectively). In post-hoc analysis iPTH were significantly higher in subjects with severe 25OHD deficiency compared to those with deficient, insufficient and sufficient 25OHD levels (P<0.0001 for all). Nevertheless, iPTH were not significantly different when subjects with deficient 25OHD were compared with those who had insufficient and sufficient 25OHD levels (P>0.05 for all). In ROC analysis the overall sensitivity and specificity for the best iPTH cut-off value (62.5 pg/ml) in subjects with low 25OHD were 65.3 and 64.8% respectively.

Conclusions: Despite of a significantly higher iPTH levels in subjects with severe 25OHD deficiency, neither iPTH nor Ca and P have sufficient sensitivity and specificity to precisely predict vitamin D deficiency.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.