High Prevalence of Hypovitaminosis D among Free-Living Postmenopausal Women Referred to an Osteoporosis Outpatient Clinic in Northern Italy for Initial Screening

Abstract:

To establish the prevalence of hypovitaminosis D among free-living postmenopausal women referred to an osteoporosis outpatient clinic in Northern Italy, we evaluated 25-hydroxyvitamin D (25(OH)D) levels in 570 postmenopausal women who had been consecutively referred to our clinic in the 12 months beginning October 1995. Parathyroid hormone (PTH), serum calcium (Ca), creatinine (Cr) and osteocalcin (OC), urinary calcium (Ca24h) and creatinine (Cr24h), and the bone mineral density of the lumbar spine (LBMD) and femur (FBMD) were also measured. 1,25-Dihydroxyvitamin D (1,25(OH)₂D) concentrations were measured in 23 women. All women had normal electrolyte serum concentrations and kidney function. Mean ± SD 25(OH)D concentration was 18.3 ± 8.3 ng/ml. A significant (p<0.001) seasonal variation was seen for both 25(OH)D and PTH. Women were divided into two groups based on their vitamin D status: low vitamin D status (25(OH)D <12 ng/ml, n= 161, 28%) and normal vitamin D status (25(OH)D ≥12 ng/ml, n= 409, 72%). Hypovitaminosis D was found in 38.5% of all the women in the time period December–May and in 12.5% in the other half-year; among women >70 years old 51% had hypovitaminosis D in the time period December–May and 17% in the other half-year. PTH was significantly (p<0.05) increased, and Ca24h, OC and FBMD significantly (p<0.05) decreased in women with hypovitaminosis D. 1,25(OH)₂D positively correlated with 25(OH)D (p<0.0001), but did not correlate with PTH, age or creatinine clearance. In conclusion, hypovitaminosis D is an important, underestimated problem in Italian free-living postmenopausal women referred to an outpatient osteoporosis clinic.