Subclinical Hypothyroidism is Related to Lower Heel QUS in Postmenopausal Women

Abstract

Abstract. Recent findings suggest that thyroid stimulating hormone (TSH) is a negative regulator of skeletal remodeling by reducing both differentiation of osteoblasts and formation of osteoclasts. In addition, increased fracture risk in untreated hypothyroid patients has been reported to begin up to 8 years before diagnosis. The aim of the present study was to evaluate the effect of subclinical hypothyroidism on bone structure by using the heel QUS. Subjects were outpatients without any past or present history of thyroid disease. Among 210 postmenopausal women, 22 of 33 patients (Hypo), who had elevated serum TSH concentration (TSHõ4 µU/ml) with normal serum free thyroxine (FT 4 ) concentration, agreed to join to this study. We also randomly selected 24 control subjects (Cont) from 176 postmenopausal women with normal thyroid status. Calcaneus osteo sono assessment indices (OSI) of right feet were measured using the ultrasound bone densitometry AOS-100. Serum TSH concentrations in Hypo patients (5.31 ± 1.3 µU/ml) were higher than those in Cont patients (2.05 ± 1.1 µU/ml), and there was significant difference of FT 4 concentrations (Cont 1.33 ± 0.15 ng/dl; Hypo 1.19 ± 0.17 ng/dl). OSI and its Z-score in Hypo subjects (OSI, 2.138 ± 0.152; Z-Score -0.322 ± 0.504 SD, Mean ± SD) were significantly lower than those in Cont subjects (OSI, 2.347 ± 0.243; Z-Score 0.322 ± 0.91 SD, Mean ± SD). Simple regression statistical analysis showed that OSI decreased according to the increase of serum TSH concentration (n = 47, P<0.037). In addition, multiple regression analysis showed that the elevation of serum TSH concentration was associated with the decrease of OSI. These results suggest that the elevation of serum TSH concentration in subclinical hypothyroidism affects not bone turnover but bone structure as assessed by QUS.

Bone health in children with long–term idiopathic subclinical hypothyroidism

“…The results of the study showed that men with high TSH levels, but lower than 10 mIU/L, had an increased risk of fracture, thus suggesting that even mild subclinical hypothyroidism may have deleterious effects on bone. Moreover, Nagata et al [37] recently reported that calcaneus osteosonographic assessment indices of right feet, measured using the quantitative ultrasound, were lower in postmenopausal women with SH than in controls.…”

The Role of FSH and TSH in Bone Loss and Its Clinical Relevance

“…The correlation was especially strong between increasing serum TSH within the reference range and increasing bone mass in both Caucasian and African American women [42]. Another prospective study showed that euthyroid women with serum TSH in the lower tertile of the normal range had a higher incidence of vertebral fractures; these findings were independent of age, BMD, and thyroid hormones [60,61].…”

Thyroid-stimulating hormone, thyroid hormones, and bone loss

“…There was a particularly strong correlation between increasing serum TSH within the reference range and increasing bone mass in both black and white American women [20]. Finally, in limited observations, serum TSH in patients receiving thyroxine has been correlated with indices of bone microarchitecture in vivo, using heel ultrasound measurements, but no fi rm conclusions can be drawn from these studies [40]. Thus, though it is clear that TSH levels correlate positively with bone density and are inversely related to bone turnover markers, a cause-effect relationship is unlikely to emerge from such studies.…”