Calcidiol and PTH levels in women attending an osteoporosis program

We performed a retrospective study of 237 patients attending a specialty os teoporosis practice. Secondary causes for reduced bone mineral density (BMD ) were evaluated in 196 postmenopausal women and 41 premenopausal women; me an age was 56 +/- 13.8 years (mean +/- SD). BMD was measured by dual-energy X-ray absorptiometry (DXA) (QDR 1000W/2000 Hologic). Levels of intact para thyroid hormone (iPTH), calcidiol [25(OH)D], thyroid-stimulating hormone, a nd 24-hour urinary calcium were measured, and serum and urine protein (SPEP and UPEP) electrophoresis were performed. Overall, 16% of our patients had 25(OH)D levels <15 ng/ml, the lowest acceptable vitamin D level without a concomitant rise in iPTK levels. Among the osteoporotic patients (T score < -2.5 SD), 17% had 25(OH)D levels <15 ng/ml and 7% <10 ng/ml. Among the oste openic patients (-2.5 < T < -1.0 SD), 11% had 25(OH)D levels <15 ng/ml. Sev enteen percent of patients with Z score less than or equal to-1.0 SD (low r ange normal value) had 25(OH)D levels <15 ng/ml. Low 25(OH)D levels were in versely related to high iPTH values (r = 0.30, P < 0.0001). Hypercalciuria was present in 15% of our patients, elevations of PTH levels (>65 pg/ml, up per normal limit of assay) were present in 11.5%, and hyperthyroidism in 4% . A 25(OH)D level of <25 ng/ml in women (n = 86) with no known secondary ca uses of low BMD was associated with an iPTH level above 49 pg/ml. The measu rement of 25(OH)D levels is recommended in the evaluation of secondary caus es for reduced BMD. Supplementation with vitamin D appears needed to keep 2 5(OH)D above 25 ng/ml, the level required to prevent increments in iPTH lev els.