Bone mass and metabolism in women aged 45-55.
OBJECTIVE
Changes in calcium homeostasis and bone mass around the climacteric are poorly understood. We examined relations between endocrine factors and indices of bone mass and metabolism in healthy women approaching the menopause.


METHODS
Cross-section study.


METHODS
Sixty-eight spontaneously menstruating women aged 45-55.


METHODS
Bone density measured at lumbar spine (LS) and femoral neck (FN) using dual energy X-ray absorptiometry and distal non-dominant forearm using peripheral quantitative computed tomography. We recorded menstrual history, physical activity and dietary calcium, and measured serum calcium, phosphate, alkaline phosphatase, osteocalcin, vitamin D, fT3, T4, TSH, PTH, FSH and oestradiol (E2), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) excretion.


RESULTS
Using serum FSH level as a marker of ovarian function, 63 subjects could be classified into one of three groups: group A (serum FSH < 10 U/l, n = 29), group B (10-35 U/l, n = 27) and group C (> 35 U/l, n = 7). Bone density fell with declining ovarian function at the LS, FN and forearm trabecular (but not cortical) sites. Serum PTH was lower in group A vs B (mean (SD) 2.68 (0.97) vs 3.52 (1.17) pmol/l, P < 0.05), but similar to group C (2.90 (1.09) pmol/l, P = NS). Serum phosphate was elevated in group C compared to groups A and B (1.17 (0.15) vs 1.04 (0.11) and 1.05 (0.13) mmol/l, P < 0.05), and urinary PYD (61.1 (8.0) vs 50.4 (11.6) and 43.9 (8.1) mumol/mol creatinine) and DPD (15.9 (3.9) vs 12.0 (3.6) and 11.4 (3.6) mumol/mol creatinine) excretion were also increased. There were no significant differences in vitamin D metabolites or osteocalcin. Multivariate analysis suggested serum osteocalcin was positively related to physical activity and serum 1,25-dihydroxycholecalciferol levels. Serum free T3 was positively correlated with urinary DPD excretion, and inversely related to serum PTH. In all subjects, serum PTH was related to body weight (r = 0.38, P = 0.002).


CONCLUSIONS
Declining ovarian function before menopause is accompanied by reductions in bone mass and altered calcium metabolism. Free T3 may regulate bone resorption and indirectly modulate PTH release.
Garton
M
M
Department of Rheumatology, Aberdeen Royal Hospitals NHS Trust, UK.
Martin
J
J
New
S
S
Lee
S
S
Loveridge
N
N
Milne
J
J
Reid
D
D
Reid
I
I
Robins
S
S
D000596:Amino Acids / Q000652:urine; D015519:Bone Density / Q000502:physiology*; D002117:Calcitriol / Q000097:blood; D002136:Calcium, Dietary / Q000008:administration & dosage; D003430:Cross-Sectional Studies; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood; D017697:Premenopause / Q000378:metabolism*; D014284:Triiodothyronine / Q000097:blood
D000596:Amino Acids; D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D010710:Phosphates; D014284:Triiodothyronine; D015675:Osteocalcin; C015484:pyridinoline; D005640:Follicle Stimulating Hormone; C036020:deoxypyridinoline; D002117:Calcitriol