Age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of bone metabolism in Chinese women.
OBJECTIVE
To study the age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of calcium metabolism in Chinese women who habitually have a low calcium intake.


METHODS
Cross-sectional study.


METHODS
One hundred and fifty-six healthy Chinese women aged 20-83 years. None were on any medication or vitamin supplements. Subjects over the age of 60 years were all living in a hostel; younger subjects were nurses or subjects attending a family clinic for minor illnesses.


METHODS
Fasting blood and urine samples were collected for biochemical measurements and calcium absorption was measured using 45Ca by the method of Marshall and Nordin. Bone density was measured by dual energy X-ray densitometry (Norland X R20 X-ray bone densitometer) at the left hip and lumbar spine. Serum parathyroid hormone was measured by a chemiluminometric assay.


RESULTS
Plasma ionized calcium concentration, alkaline phosphatase, bicarbonate, plasma creatinine and serum B2 microglobulin were significantly higher in the elderly than in the young, whereas plasma phosphate and the anion gap were higher in the young. Urinary excretion of calcium, phosphate and hydroxyproline were all higher in older women. Plasma parathyroid hormone concentration was positively correlated with age even after taking into account the decline in renal function (as indicated by the rise in B2 microglobulin (r = 0.506, P less than 0.001). Serum concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were not lower in the older women. Fractional calcium absorption from an oral load of radiolabelled calcium was significantly lower in the older women and 37% of the older women were below the 2.5 percentile found in the younger women. Bone density measured by dual energy X-ray densitometry was also significantly lower in the elderly.


CONCLUSIONS
In Chinese women there is an increase in PTH and a decrease in calcium absorption with age in spite of the presence of normal vitamin D metabolites.
Chan
E L
EL
Department of Chemical Pathology, Prince of Wales Hospital, Shatin, NT, Hong Kong.
Lau
E
E
Shek
C C
CC
MacDonald
D
D
Woo
J
J
Leung
P C
PC
Swaminathan
R
R
D000042:Absorption; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002681:China; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*
D010281:Parathyroid Hormone; D000469:Alkaline Phosphatase; D002118:Calcium