The 25(OH)D/PTH threshold in black women.

Abstract

Black women have lower 25-hydroxyvitamin D [25(OH)D] and higher PTH than white women. Recent evidence implicates PTH in adverse cardiovascular outcomes. The objective of the study was to determine whether PTH increases at lower 25(OH)D levels (the threshold) in black compared with white women. Healthy black and white women, aged 20-80 yr were recruited to participate in a cross-sectional study of body-composition in black and white women. Measurement of serum 25(OH)D and PTH were carried out. The study was a convenience sample recruited from a community setting. Healthy black and white women were recruited by advertising and a direct mail campaign in a comparative study of body composition. Age ranged from 20-to 80 yr. There were 148 black and 129 white premenopausal participants and 87 black and 139 white postmenopausal participants. The main outcome was to determine whether the threshold for 25(OH)D/PTH differs in black and white women. A threshold of 37 nmol/liter (95% confidence interval 35-40) was found for black and 59 nmol/liter (95% confidence interval 56-63) for white women. These two values were significantly different (P < 0.001). Black women have an increase in serum PTH at a lower 25(OH)D level than white women. Negative health outcomes of higher PTH should be investigated in black women.