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A longitudinal study of bone-related biochemical changes at the menopause
B E Christopher Nordin1, Judith M WIshart, Peter M Clifton
1Division of Clinical Biochemistry, Institute of Medical and Veterinary Science, Department of Medicine, University of Adelaide, Adelaide, Australia. christopher.nordin@imvs.sa.gov.au
Clinical Endocrinology
|June 24, 2004
Summary
Menopause significantly alters bone metabolism, increasing serum calcium and bone resorption markers. These changes, despite stable parathyroid hormone, suggest a shift in hormonal regulation and increased bone sensitivity, impacting calcium absorption and renal handling.
Area of Science:
- Bone and mineral metabolism
- Endocrinology
- Menopause research
Background:
- Menopause is associated with significant skeletal changes.
- Understanding biochemical alterations during menopause is crucial for bone health.
- Estrogen deficiency impacts calcium homeostasis and bone turnover.
Purpose of the Study:
- To longitudinally evaluate the effects of menopause on bone-related biochemical variables.
- To assess changes in calcium metabolism and bone turnover markers before and after the menopausal transition.
Main Methods:
- Longitudinal study of 104 premenopausal women (age >44).
- Annual collection of blood and urine samples for biochemical analysis.
- Measurement of radiocalcium absorption, vitamin D metabolites, PTH, and bone resorption markers.
Main Results:
- Significant 'tracking' of most variables across menopause was observed.
- Rises in serum total and ionized calcium (P < 0.001) without change in PTH.
- Decreased radiocalcium absorption (P < 0.001) and increased urinary calcium (P < 0.001) indicating reduced renal tubular reabsorption.
- Increased urinary bone resorption markers (pyridinoline and deoxypyridinoline) (P < 0.001).
Conclusions:
- Menopause-induced rise in ionized calcium suggests a change in PTH set-point.
- Reduced calcium absorption and reabsorption reflect loss of estrogen action.
- Increased bone resorption, despite normal PTH, indicates heightened bone sensitivity to PTH.
- Significant tracking of variables occurs despite substantial absolute value changes.