Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Biochemistry

Background/Aims: The last decade has witnessed a tremendous interest in vitamin D, based on the awareness of the worldwide high prevalence of vitamin D deficiency. Subject and method: the study population consisted of one hundred two healthy adolescent females enrolled in Helwan University, Egypt. The subjects classified by vitamin D status after screening as following, sufficient (G1), insufficient (G2), and deficient group (G3). Females completed a questionnaire regarding sun exposure duration, use of topical sunscreens and performed anthropometric measures, 25-hydroxycholecalciferol 25(OH)D, vitamin D binding protein (DBP), total calcium, calcium ionized, calcitonin, homocysteine, hs-CRP, TSH levels, alkaline phosphatase, inorganic phosphate, PTH, Albumin were all determined. The bioavailable 25(OH)D levels were calculated using 25(OH)D, DBP, and albumin concentrations. Results: 25(OH)D, vitamin D binding protein, calculated free vitamin D, bioavailable vitamin D, total calcium, calcium ionized, and calcitonin, were significantly decreased in the deficient (G3) and insufficient (G2) in comparison to the sufficient group (G1) (P<0.01). Homocysteine, hs-CRP, and TSH levels were significantly increased of the deficient (G3) in comparison to the sufficient group (G1) (P<0.01). Conclusion: Our study demonstrated a high prevalence of vitamin D insufficiency and deficiency about (54.9%) among healthy Egyptian adolescent females. Vitamin D showed a significant positive correlation with serum total calcium, calcium ionized, calcitonin, vitamin D binding protein (DBP), calculated free vitamin D, bioavailable vitamin D, and sun exposure duration

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