Influence of Low Total Triiodothyronine Levels on Bone Turnover Markers in Type 2 Diabetes Mellitus

Abstract

Purpose: The aim of this study was to investigate whether low total triiodothyronine (TT3) could affect bone turnover in patients with type 2 diabetes mellitus (T2DM).

Materials and methods: This is a cross-sectional study that recruited 577 patients with T2DM, 141 patients formed the low TT3 group (TT3<1.30nmol/L) and 436 patients formed the control group (TT3≥1.30nmol/L), and the low TT3 group was further subdivided into four groups based on the TT3 level. To investigate whether TT3 level is associated with poor glycemic control, all participants were divided into high glycosylated hemoglobin (HbA1c) group and low HbA1c group using HbA1c 10.5% as the boundary.

Results: The levels of OC and PINP were significantly lower in the low TT3 group compared with the control group (P < 0.05). TT3 positively correlated with OC and PINP (r = 0.219, P = 0.009; r = 0.208, P = 0.019) in the low TT3 group, and this positive correlation still existed after adjusting for other factors in multilinear regression analysis. Next, we want to find a cut-off point to prevent osteoporosis, we divided the patients in the low TT3 group into four groups based on the TT3 level, the levels of OC and PINP were significantly lower in the TT3 < 1.00 nmol/L group than in the TT3 ≥ 1.00 nmol/L groups.

Conclusion: In patients with T2DM, low TT3 levels are associated with impaired bone formation. What's more, bone formation was significantly impaired when TT3 was <1.00 nmol/L.

Keywords: bone turnover markers; low TT3 level; thyroid hormones; type 2 diabetes mellitus.

Figure 1

Comparisons of bone turnover markers levels in low TT3 group and control group in patients with type 2 diabetes mellitus. (A) Comparisons of OC levels in low TT3 group and control group in patients with type 2 diabetes mellitus. (B) Comparisons of β-CTX levels in low TT3 group and control group in patients with type 2 diabetes mellitus. (C) Comparisons of PINP levels in low TT3 group and control group in patients with type 2 diabetes mellitus.

Figure 2

The correlation between bone turnover markers levels and TT3 levels in the low TT3 group. (A) The correlation between OC levels and TT3 levels in the low TT3 group. (B) The correlation between β-CTX levels and TT3 levels in the low TT3 group. (C) The correlation between PINP levels and TT3 levels in the low TT3 group.

Figure 3

BTMs of patients with T2DM and low TT3 levels, stratified according to serum TT3 levels. (A) Comparisons of OC levels in four groups. (B) Comparisons of β-CTX levels in four groups. (C) Comparisons of PINP levels in four groups.Group 1: TT3 < 1.00 nmol/L; Group 2:1.00 nmol/L ≤ TT3 < 1.10 nmol/L; Group 3:1.10 nmol/L ≤ TT3 < 1.20 nmol/L; and Group 4: 1.20 nmol/L ≤ TT3 < 1.30 nmol/L.