الفهرس 
VITAMIN D PHYSIOLOGY AND STRUCTUREOnly 14 pages are availabe for public view
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Abstract
T
he Vitamin D deficiency pandemic increases the entire world’s population risk of the most serious chronic illnesses including deadly cancers, type 2 diabetes, heart disease, stroke, autoimmune diseases, asthma and infectious diseases. Thus there is a need to increase the awareness of the medical community and public about the insidious consequences of Vitamin D deficiency.
Although Vitamin D deficiency is prevalent, measurement of serum 25 (OH) D levels is expensive, so Vitamin D testing is limited to those at risk for severe deficiency and universal screening is not supported.
The aim of this study is to investigate markers of Vitamin D deficiency applicable in large sectors of society at low cost to diagnose such a widely prevalent condition with reasonable cost benefit ratio.
Our study was conducted on 90 healthy adults aged (20-60) ys. Outpatients with minor intercurrent illness, companions of in-patient and healthy hospital workers were volunteers in our study. Samples collected from participants in Cairo (L=30o), during the winter and spring from December to April.
All participants were subjected to full medical history taking, General clinical examination and Laboratory investigations including (Hb, S.creatinine, total, ionized Ca, phosphorus, Mg, intact PTH (i- PTH) and 25 hydroxy Vitamin D level). Subjects with chronic systemic diseases were excluded from our study.
We classified our volunteers according to Vitamin D status into:
Group Ι: Vitamin D deficient group, with Vitamin D level below < 20 ng/ml.
Group ΙΙ: Vitamin D insufficient group, with Vitamin D level between 20-29 ng/ml.
Group ΙΙΙ: Vitamin D sufficient group, with Vitamin D level 30-100 ng/ml.
According to gender into:
Group M: males
Group F: females
According to BMI into:
Group N: non obese, with BMI <30 Kg/m 2
Group O: obese, with BMI ≥ 30 Kg/m 2
Our results revealed the following:
On comparing Group Ι (Vitamin D deficient group) with Group ΙΙ (Vitamin D insufficient group), we found that, there was highly significant statistically difference between both groups in PTH (p-value < 0.001), but There was no significant statistical difference between both groups in age (p-value> 0.05), HB (p-value > 0.05), Creat (p-value > 0.05), total Ca (p-value > 0.05), ionized Ca (p-value > 0.05), PO4 (p-value > 0.05) Ca-PO4 Product (p-value > 0.05), Mg (p-value > 0.05) and BMI (p-value > 0.05).
On comparing Group M (males) with Group F (females) we found that, there was highly significant statistical difference between both groups in HB (p-value < 0.001)and there was significant statistical difference between both groups in Creat (p-value < 0.05), PO4 (p-value < 0.05) Ca-PO4 Product (p-value < 0.05), but there was no significant statistical difference between both groups in age (p-value> 0.05), BMI (p-value> 0.05), total Ca (p-value > 0.05), ionized Ca (p-value > 0.05), Mg (p-value > 0.05), PTH (p-value > 0.05) and Vit.D (p-value > 0.05).
On comparing Group N (non obese) with Group O (obese) we found that, there was highly significant statistical difference between both groups in age (p-value < 0.001) and there was significant statistical difference between both groups in total Ca (p-value < 0.05), PO4 (p-value < 0.05) Ca-PO4 Product (p-value < 0.05), but there was no significant statistical difference between both groups in HB (p-value> 0.05), BMI (p-value> 0.05), Creat (p-value > 0.05), ionized Ca (p-value > 0.05), Mg (p-value > 0.05), PTH (p-value > 0.05) or Vit. D (p-value > 0.05).
On correlating different parameters with each others we found that, there was highly significant positive correlation between BMI and age (r=0.4) and between Ca and ionized Ca(r=0.7) and There was a positive significant correlation between HB and Creat. (r=0.2), there was also a negative significant correlation between age and PO4(r=-0.2), between BMI and PO4 (r= -0.3), between Vit.D and PTH (r=-0.2), but a non significant correlation found between other parameters.
ROC curve done to assess the predictive accuracy of PTH, total calcium, ionized calcium, phosphorous and calcium phosphorous product as markers for Vitamin D status, results showed that PTH with cut off value 51 pg/ml has sensitivity 85% and specificity 45% with predictive accuracy 70%, while total calcium with cut off value 9.5 mg/dl has sensitivity 31.4% and specificity 60% with predictive accuracy 38%, ionized calcium with cut off value 4.6 mg/dl has sensitivity 21% and specificity 70% with predictive accuracy 43%, phosphorous with cut off value3.5 mg/dl has sensitivity 30% and specificity 75% with predictive accuracy 60.7%, while calcium phosphorous product with cut off value 40 has sensitivity71% and specificity 55% with predictive accuracy 59.2%.
In conclusion, our results revealed that, PTH can be used as a surrogate marker for Vitamin D to reflect its status; hyperparathyroidism despite normal calcium and creatinine indicates Hypovitaminosis D. Age and BMI should be taken into consideration as they can modulate PTH/25(OH)D relationship. The blunted PTH response that may coexist with Hypovitaminosis D due to Mg deficiency should also be taken into consideration.