Marianna Katrinaki1, Marilena Kampa2,3, Andrew Margioris1,4, Elias Castanas2,3, Niki Malliaraki5. 1. Laboratory of Clinical Chemistry-Biochemistry, University Hospital of Heraklion, P.O. Box 1352, Heraklion, 71110, Greece. 2. Laboratory of Experimental Endocrinology-Clinical Immunology, University Hospital, Heraklion, Crete, Greece. 3. Laboratory of Experimental Endocrinology-Clinical Immunology, University of Crete, School of Medicine, Heraklion, Crete, Greece. 4. Laboratory of Clinical Chemistry, University of Crete, School of Medicine, Heraklion, Crete, Greece. 5. Laboratory of Clinical Chemistry-Biochemistry, University Hospital of Heraklion, P.O. Box 1352, Heraklion, 71110, Greece. nmalliaraki@pagni.gr.
Abstract
OBJECTIVE: The determination of the normal range of 25-hydroxyvitamin D [25-(OH)D], though currently based on suppression of PTH levels, still remains a controversial issue. The 25-(OH)D levels exhibit gender and seasonal variability, the latter attributed in part to changes of insolation. DESIGN: The aim of this cross-sectional study was to estimate the levels of 25-(OH)D on the island of Crete and their correlation with metabolic, hormonal and bone turnover parameters. The study was performed over a period of five years and involved 8,183 male and female individuals (8,042 analyzed). RESULTS: Our results are as follows: (1) 25-(OH)D was significantly lower than expected (19.48±9.51 and 18.01±9.01 (ng/mL+SD) in males and females, respectively); (2) seasonal variation of 25-(OH)D was observed in both sexes (females < males), with values peaking in August; (3) a decline of 25-(OH)D was evident with advancing age, with lower levels in females compared to males up to menopause and no apparent difference between the genders thereafter; (4) levels of 25-(OH)D were lower in renal function impairment, diabetes/insulin resistance and inflammation, while no correlation was detectable in thyroid dysfunction; (5) normalization of PTH levels was observed at ~20 ng/mL 25-(OH)D. At the same cut-off level, a significant decrease of all measured bone turnover indices (b-ALP, osteocalcin and CTX) was evident. CONCLUSION: Based on the above data, it appears that a cut-off level of 25-(OH)D close to 20 ng/mL better reflects the physiology of our population.
OBJECTIVE: The determination of the normal range of 25-hydroxyvitamin D [25-(OH)D], though currently based on suppression of PTH levels, still remains a controversial issue. The 25-(OH)D levels exhibit gender and seasonal variability, the latter attributed in part to changes of insolation. DESIGN: The aim of this cross-sectional study was to estimate the levels of 25-(OH)D on the island of Crete and their correlation with metabolic, hormonal and bone turnover parameters. The study was performed over a period of five years and involved 8,183 male and female individuals (8,042 analyzed). RESULTS: Our results are as follows: (1) 25-(OH)D was significantly lower than expected (19.48±9.51 and 18.01±9.01 (ng/mL+SD) in males and females, respectively); (2) seasonal variation of 25-(OH)D was observed in both sexes (females < males), with values peaking in August; (3) a decline of 25-(OH)D was evident with advancing age, with lower levels in females compared to males up to menopause and no apparent difference between the genders thereafter; (4) levels of 25-(OH)D were lower in renal function impairment, diabetes/insulin resistance and inflammation, while no correlation was detectable in thyroid dysfunction; (5) normalization of PTH levels was observed at ~20 ng/mL 25-(OH)D. At the same cut-off level, a significant decrease of all measured bone turnover indices (b-ALP, osteocalcin and CTX) was evident. CONCLUSION: Based on the above data, it appears that a cut-off level of 25-(OH)D close to 20 ng/mL better reflects the physiology of our population.