Figure 1:

Relationship between PTH (normal range 1.6–9.3 pmol/L) and 25(OH)D₃ levels. There was no linear correlation between PTH and 25OHD₃ levels, but using a polynomial curve, the correlation coefficient was significant at 0.55.

Legend: PTH = parathyroid hormone; 25(OH)D₃ = vitamin D₃.