Thyroid. 2006 Jun;16(6):583-91

Heemstra KA, Hamdy NA, Romijn JA, Smit JW.

Patients with differentiated thyroid carcinoma (DTC) are commonly treated long-term with thyrotropin (TSH)- suppressive thyroxine replacement therapy resolving in a state of subclinical hyperthyroidism. The relationship between subclinical hyperthyroidism and osteoporosis is not clear. In this review, we systematically selected and analyzed 21 studies addressing this issue. Although multiple methodological differences between studies prevented a structured meta-analysis, our data suggest that postmenopausal women with subclinical hyperthyroidism are most at risk, whereas no increased risk was observed in men and premenopausal women. Based on these findings we believe that measurement of bone mineral density is recommended in postmenopausal women with DTC starting TSH suppressive therapy. This should be subsequently regularly measured to enable timely intervention with bone protective agents.

Ann N Y Acad Sci. 2006 Apr;1068:309-18

Sun L, Davies TF, Blair HC, Abe E, Zaidi M.

We have recently challenged the view that the bone loss associated with hyperthyroidism is solely due to elevated thyroid hormone levels. We find that thyroid-stimulating hormone (TSH), derived from the anterior pituitary gland, inhibits bone resorption by the osteoclast. Mice haploinsufficient in the TSH receptor show reduced bone density and evidence of enhanced bone resorption in the face of normal thyroid function. In humans, TSH inhibits markers of bone resorption with a single administration, and low TSH levels correlate with increased fracture risk. The evidence that low TSH levels predispose to osteoporosis in hyperthyroidism is discussed in view of the emerging role of pituitary hormones in bone biology.

Ann Endocrinol (Paris). 2006 Mar;67(1):27-31

Safi S, Hassikou H, Hadri L, Sbihi A, Kadiri A.

Osteoporosis is a common complication of hyperthyroidism, but it is not often evaluated. The aim of this study is to examine bone mineral density (BMD) (dual energy X-ray absorptiometry: DEXA) in lumbar spine (L1-L4), femoral neck (FN) and Ward's triangle (TW) in 45 hyperthyroid patients (group A: n 25 active hyperthyroidism, group B: n 20 controlled hyperthyroidism on medical therapy, after a mean of 7 months of euthyroidism), compared to control group (group C: n 22). These 3 groups are adjusted by age, sex, menopausal status and BMI. In hyperthyroid patients (group A), as compared to the control group, we noticed a significant reduction of BMD (z score) in different sites, more markedly in the lumbar spine (p L1-L4: 0,005; p FN: 0,011; p TW: 0,019). In group A, no differences were found between BMD values after adjustment for Z score whatever the menopausal status (p L: 0.12; p FN: 0.33; p TW: 0.09) and degree of hyperthyroidism (p L: 0.48; p FN: 0.41; p TW: 0.21). The degree of BMD in group B patients was different from that of patients in group A (p L: 0.37; p FN: 0.28; p TW: 0.31) and was significantly lower than in those of group C except for the TW (p L: 0.009; p CF: 0.038; p TW: 0.068). We conclude that it is important to consider that after reaching euthyroidism hyperthyroidism patients present a bone risk.

Clinical Endocrinology Volume 64 Page 86  - January 2006

Duk Jae Kim*, Young Ho Khang†, Jung-Min Koh*, Young Kee Shong* and Ghi Su Kim*

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). Design: A cross-sectional hospital-based survey. Participants: Nine hundred and fifty-nine healthy postmenopausal women. Measurements: 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/cm2vs 0·900 ± 0·009 g/cm2, P = 0·004) and femoral neck (0·660 ± 0·006 g/cm2vs 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). Conclusion: 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.