Bone loss at the femoral neck in premenopausal white women: effects of weight change and sex-hormone levels.

To investigate whether bone loss occurs in the premenopause, we measured the bone mineral content (BMC), bone mineral density (BMD), and bone area in the spine (L2-L4), femoral neck, and total hip, as well as the sex hormone levels of 130 healthy premenopausal white women (age, 31-50 yr) at least three times over 1-9 yr. We found an increase in all three bone measurements at the spine but no change in volumetric density. Neither could we detect any age-related changes in any of the three measurements in the total hip. In contrast, we detected a significant decrease in femoral neck BMD over time, due to a decrease in BMC and increase in bone area. Greater loss in femoral neck BMD was associated independently with weight loss and lower levels of estrone sulfate or E2. Separating the women into those with FSH spikes (>20 IU/liter) and women with consistently low FSH, we found the latter group had smaller decrease in BMD and that the decrease was due less to a decline in BMC and more to an increase in bone area. In summary, femoral neck BMD decreases in premenopausal women, particularly those with lower levels of estrogens resulting from slowing ovarian function despite regular menses. This decrease can be offset by more rapid weight gain.