Serum Parathyroid Hormone in Healthy Japanese Women in Relation to Serum 25-Hydroxyvitamin D

The aim of this work was to clarify levels of serum parathyroid hormone (PTH) in healthy adult women and to study the relationship between PTH and 25-hydroxyvitamin D [25(OH)D]. One hundred sixty-nine healthy women aged 40 years or older in a community were studied. The average age of the subjects was 65.3 years (SD 8.2). All subjects had normal serum creatinine levels. Serum intact PTH and 25(OH)D were measured in these subjects. The mean intact PTH concentration was 2.19 pmol/A (SD 1.02). High intact PTH levels above the reference range were observed in four women (2.4%), all of whom were aged 70 years or older. Intact PTH increased with age with a correlation coefficient of 0.192 (p = 0.013). However, there was no correlation (r = –0.125, p = 0.105) between intact PTH and 25(OH)D whose concentrations were more than 37.5 nmol/l. In conclusion, PTH levels of healthy adult Japanese women are lower than previous reports from Western countries, which may be due to the high 25(OH)D levels of the present subjects and/or an ethnic difference. In addition, there is no association between serum 25(OH)D and PTH levels in this Japanese population, supporting a cutoff level of 25(OH)D less than 37.5 nmol/l for the elevated PTH level.