  Women are at increased risk of bone loss during the menopausal transition; in
fact, nearly 50\% of women's lifetime bone loss occurs during this time. The
longitudinal relationships between estradiol (E2) and follicle-stimulating
hormone (FSH), two hormones that change have characteristic changes during the
menopausal transition, and bone health outcomes are complex. However, in
addition to level and rate of change in E2 and FSH, variability in these
hormones across the menopausal transition may be an important predictor of bone
health, but this question has yet to be well explored. We introduce a joint
model that characterizes individual mean estradiol (E2) trajectories and the
individual residual variances and links these variances to bone health
trajectories. In our application, we found that higher FSH variability was
associated with declines in bone mineral density (BMD) before menopause, but
this association was moderated over time after the menopausal transition.
Additionally, higher mean E2, but not E2 variability, was associated with
slower decreases in during the menopausal transition. We also include a
simulation study that shows that naive two-stage methods often fail to
propagate uncertainty in the individual-level variance estimates, resulting in
estimation bias and invalid interval coverage
