Objective: To evaluate the nutritional status of vitamin D in relation
to calcium-regulating hormones and related minerals. Methods: A prosp
ective study was conducted of 451 Saudi subjects (172 males, 279 femal
es) living in the Jeddah area. Serum calcidiol and calcitriol concentr
ations were measured together with concentrations of serum intact-para
thyroid hormone (PTH), calcitonin, vitamin D binding protein (DBP), al
kaline phosphatase, calcium, phosphate and magnesium in the studied Sa
udi subjects. Results: The overall means for serum calcidiol and calci
triol were 48.15 nmol/l and 82.55 nmol/l, respectively. No significant
difference was observed between serum calcidiol and calcitriol values
among males and females studied. Subclinical vitamin D deficiency (se
rum calcidiol < 20 nmol/l) was observed in 23 males and 46 females giv
ing an overall rate of 15.3%. Severe biochemical vitamin D deficiency
(serum calcidiol <12.5 nmol/l) was observed in three males (1.74%) and
eight females (2.4%), respectively. Serum calcidiol correlated with s
erum calcitriol (r=0.773, p<0.001); calcium (r=0.227, p<0.001); intact
-PTH (r=-0.219, p<0.001) and alkaline phosphatase (r=-0.327, p<0.001),
respectively. Whereas, serum calcitriol correlated with serum calcium
(r=0.113, p<0.01); and alkaline phosphatase (r=-0.307, p<0.001), resp
ectively. Stepwise multiple-regression analysis showed that calcitriol
and phosphate contributed significantly to the variation in serum cal
cidiol with minor contributions from intact-PTH, calcitonin and calciu
m. Conclusion: These observations provide detailed information on the
nutritional status of vitamin D in the local population in relation to
calcium-regulating hormones and minerals and show that 15.3% of the s
tudied population exhibited subclinical vitamin D deficiency.