Thyroid-stimulating hormone within low-normal range is related to imbalance of bone remodeling in euthyroid postmenopausal women with osteoporotic fractures

Abstract

Introduction. Data relating to thyroid-stimulating hormone (TSH) and risk of fractures are limited, and the effect of TSH within the normal range on bone mineral density (BMD) and bone remodelling is controversial. We aimed to evaluate whether variations across TSH concentration within the normal range are associated with bone metabolism expressed by bone remodeling markers in euthyroid postmenopausal women with osteoporotic fractures.

Material and methods. The study group consisted of 60 elderly women admitted to the hospital due to nonvertebral osteoporotic fractures of which 57 were diagnosed as euthyroid. In all serum fT4, and TSH, P1NP (a bone formation marker) and CTX (a bone resorption marker) were measured.

Results. The majority of fractures occurred at the lower TSH tertile (0.14–2.19 mIU/L). Most of the patients (70%) in this tertile had TSH value below 1 mIU/L. There was a clear tendency towards lower P1NP in the first TSH tertile (p = 0.056 and p = 0.057) whereas most CTX values tended to be higher than the median concentration in the whole group. A significant positive correlation between TSH and P1NP was observed (r = 0.32; p = 0.01). TSH within the normal range and CTX explained 25% of the variability of P1NP in euthyroid women with osteoporotic fractures.

Conclusions. In elderly euthyroid women low-normal TSH level seems to be associated with the imbalance between bone resorption and formation. Diminished bone formation may predispose to increased risk of nonvertebral fractures. Bone marker testing in subjects with low-normal TSH may add new value in the assessment of fracture risk.