Self-limiting forearm bone loss in normal post-menopausal women

156 A timetable existed for most of the women in regard to the

family dimension of

their lives. The work dimension, however, did not have its own timetable, this being dictated primarily by Without an established work between the work and

events occurring within the

timetable, synchrony -

family life-cycles -

the

family dimension.

regulatory mechanism

was excluded. The implicationsas

regards women's values ware considered.

97

SELF-LIMITINGFOREARM BONE LOSS IN NORMAL POST-MENOPAUSALWOMEN

B.E. Nordin, T.

Huber, T.

Steurer, C.

Walker and

B.

Chatterton -

Adelaide, Australia

We

have suggested elsewhere that iliac crest trabecular bone volume at

equilibrium is

determined by the relation between an independent variable (bone

formation rate) and a

volume-dependent variable (fractional bone resorption

rate). We have now shown that this model can be applied to the forearm.

The

study is

based on

a

survey of approximately 500 normal postmenopausal

women in whom cross-sectionaland some longitudinalmeasurements of density have been performed. The

forearm bone

forearm densitometrywas performed with the

Molsgaard bone mineral analyzer with the arm immersed in a water bath.

The cross-sectionaldata observe an

exponential-type function when

forearm

mineral density (FMD) is regressed on years since menopause. The mean FMD at the menopause is 460 mgfml and this value falls to

a

minimum value of

360 mglml

about ten years after the menopause. The calculated mean bone formation rate in this population is 65 mg of mineral/ml/yearand

the

fractional resorption rate

Ias per annum. This implies that the net rate of bone loss in any individual is a function of the initial bone density. This is observations which are

so

far available on

borne out

190 of

by

longitudinal

these women and show a

significant correlation between initial FMD and rate of loss. Thus the high of

bone loss in

rate

women close to the menopause is a function of their high bone

density rather than of their temporal proximity to the menopause.

Within this framework there are other variables which also influence the of

bone loss. Of

these the most

excretion which in turn is related to

important appears to urea and

reflect dietary protein and sodium intake.

be

rate

urinary calcium

sodium excretion, which must

157 It was women

concluded that, since the forearm bone loss in normal post-menopausal

is

self-limiting, the

excessive bone

presumably represents continuing loss of

loss in

bone

clinical

osteoporosis

beyond the time when it should

normally have ceased. Some of the risk factors which determine this abnormal, continuing loss of bone are discussed elsewhere in this issue.

88

RELATIONSHIP BETWEEN CALCIUM ABSORPTION, SERUM DEHYDROEPIANDROSTERONEAND BONE DENSITY IN NORMAL AND OSTEOPOROTIC POST-MENOPAUSALWOMEN

B.E. Nordin, A.

Robertson, Tracy

Steurer,

Annette

Bridges,

B.E.

Chatterton, R.F. Seamark and T.F. Hartley - Adelaide, Australia

Osteoporosis is the main

undoubtedly multifactorial in origin, but identificationof

risk factors has

condition.

In

the

been handicapped by

present

study,

difficulty in

calcium

defining the

absorption

and

serum

dehydroepiandrosterone(DHA) were directly related to bone density.

The study comprised 102 post-menopausalwomen - 52 with 17 with

definite osteoporosis,

possible osteoporosis and 33 with normal spines and no fracture history.

Vertebral mineral density (VMD) was determined by scanning and

computerized tomography (CT)

forearm mineral density (FMD) with

the Molsgaard Bone Mineral

Analyser. Density was expressed as mg of bone mineral per ml. was

determined with

Calcium absorption

radiocalcium using a single blood sample obtained one hour

after the dose was administered. Serum DHA was determined by radioimmunoassay.

VMD and FMD were both very significantly lower in normal subjects (p (0.001)

with

the

the

osteoporotic than the

doubtful cases occupying an intermediate

position. Radiocalcium absorption and serum DHA were also significantly lower in the

osteoporotic than

the normal subjects (p(O.001 and ~(0.002 respectively)

with the doubtful cases occupying an and

FMD

on

age

and

intermediate position. Regression of

years since menopause showed that both were

significantly inversely related to years since menopause but

not

to

VMD very

age when

years since menopause were taken into account. Regression of VMD on years since menopause, calcium absorption and DHA showed that calcium absorption since menopause were

of

DHA was rather less significant. Conversely, regression of absorption, DHA

and

FMD

years since menopause showed that DHA

menopause were approximately equally significant, and less so.

and

years

approximately equal significance; the correlation with on

calcium

and years since

calcium absorption rather