Low normal TSH levels are associated with low bone mineral density in healthy postmenopausal women.
OBJECTIVE
Hyperthyroidism is accompanied by low bone mass. Because the reference range of TSH levels is defined statistically, some individuals with low normal TSH levels may have mild hyperthyroidism and reduced bone mass. We therefore determined whether serum TSH levels correlate with bone mineral density (BMD).


METHODS
A cross-sectional hospital-based survey. Participants Nine hundred and fifty-nine healthy postmenopausal women.


METHODS
We measured BMD at the lumbar spine and femoral neck using dual energy X-ray absorptiometry, and serum TSH concentrations using immunoluminometry.


RESULTS
BMD at the lumbar spine and femoral neck increased with TSH level (P for trend < 0.001 at both sites). Even after adjustment for age, years since menopause and body mass index, subjects with low normal TSH levels (0.5-1.1 mU/l) had significantly lower BMDs at the lumbar spine (0.863 +/- 0.009 g/cm2 vs 0.900 +/- 0.009 g/cm2, P = 0.004) and femoral neck (0.660 +/- 0.006 g/cm2 vs 0.683 +/- 0.006 g/cm2, P = 0.006) than those with high normal TSH levels (2.8-5.0 mU/l), as well as a 2.2-fold increased risk of osteoporosis (95% confidence interval: 1.2-4.0).


CONCLUSIONS
These results suggest that low normal TSH levels may not be physiological for postmenopausal women and, during treatment of hypothyroidism, may not be adequate for avoiding osteoporosis.
Kim
Duk Jae
DJ
Division of Endocrinology and Metabolism, University of Ulsan College of Medicine, Asan Medical Center, Songpa-Gu, Seoul, Korea.
Khang
Young Ho
YH
Koh
Jung-Min
JM
Shong
Young Kee
YK
Kim
Ghi Su
GS
D000368:Aged; D015992:Body Mass Index; D015519:Bone Density; D003430:Cross-Sectional Studies; D005260:Female; D005272:Femur Neck / Q000503:physiopathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood*; D012016:Reference Values; D012044:Regression Analysis; D013739:Testosterone / Q000097:blood; D013972:Thyrotropin / Q000097:blood*; D013997:Time Factors
D013739:Testosterone; D013972:Thyrotropin