Low TSH Levels Within Euthyroid Range Could Play a Negative Role on Bone Mineral Density in Postmenopausal Women with Type 2 Diabetes

High-normal free thyroxine level is related with decreased bone mineral density in nonobese male patients with type 2 diabetes over 50 years old

Background

The prevalence of 'low bone mineral density (BMD)' in Type 2 diabetes (T2DM), especially stratified by body mass index, is seldom reported. The relation of the euthyroid range and low BMD in T2DM remains to be further elucidated.

Objectives

We aim to investigate the thyroid hormones' impact on BMD among euthyroid patients with T2DM.

Design and methods

A total of 1452 hospitalized T2DM patients with normal thyroid function (43.6% males aged over 50 and 56.4% postmenopausal females) were enrolled in this cross-sectional study. BMD was measured at lumbar spine by GE lunar dual-energy X-ray absorptiometry system, and 'low BMD' was defined as T-score <-1.0 SD. The prevalence of 'low BMD' was compared between obese and nonobese (body mass index < 25 kg/m2) groups for both sexes, and the relation of low BMD and free T4 quartiles was explored by multiple logistic regression.

Results

The general prevalence of 'low BMD' was 12.3% for male patients aged over 50 (15.5% in the nonobese group and 8.0% in the obese group) and 49.8% for postmenopausal females (56.7% in the nonobese group and 48.9% in the obese group). After adjustment in multiple linear regression, free T4 level remained significantly related to decreased BMD in nonobese male subgroup. Multiple logistic regression revealed that BMD of the highest free T4 quartile (1.12-1.48 ng/dL) decreased significantly than other three quartiles after adjusting for confounding factors including age, body mass index, serum calcium and creatinine level, fasting glucose, alkaline phosphatase, glycosylated hemoglobin, total cholesterol, and smoking history (OR = 2.724, 95% CI = 1.085-6.840, p = 0.033). No significant relation was found in obese male or postmenopausal female groups.

Conclusion

High-normal free T4 is a potential independent risk factor for 'low BMD' in nonobese male T2DM patients aged over 50. Close attention should be paid to thyroid function profile, even within normal range, in nonobese men with underlying higher fracture risks on diabetes status.

Effect of Thyroxine and Thyrotropin on Bone Mineral Density in Postmenopausal Women: A Systematic Review

The effect of thyroid hormones on bone mineral density in postmenopausal women has been reported but is not completely established. To better understand this relationship, this systematic review of the reported association, differences, and effects of thyroxine and/or thyrotropin levels on bone mineral density was conducted. An electronic literature search was conducted on MEDLINE, PMC, Google Scholar, Cochrane Library, and Science Direct from inception to April 2022; 20 studies were identified which include five quasi-experimental studies, three community cohort studies, and 12 hospital-based cross-sectional studies. Following an extensive evaluation, it was difficult to conclusively determine the association or effect of thyroxine or thyrotropin levels on bone mineral density in postmenopausal women. It is therefore suggested to conduct additional non-randomized or randomized control studies on this topic for the benefit of postmenopausal women. Particular attention should be given to the adjustment of age, body mass index, smoking status, alcohol consumption, and dietary calcium in future research on this topic for rigorous analysis.

The Comparative Study on the Status of Bone Metabolism and Thyroid Function in Diabetic Patients with or without Ketosis or Ketoacidosis

PURPOSE

This study aims to identify changes in bone turnover markers and thyroid function in diabetic ketosis (DK) and diabetic ketoacidosis (DKA).

MATERIALS AND METHODS

We compared data from the Department of Endocrinology at Shanghai Pudong Hospital from 2018 to 2020 on the pancreatic status and previous glucose control, bone transformation, calcium homeostasis, and thyroid function in groups with diabetes (DM alone, n=602), DK (n=232), and DKA (n=60). Similar comparisons were made in recurrent DK (A) (n=17) and single DK (A) (n=272).

RESULTS

The fasting C-peptide level decreased significantly, but hemoglobin A1c (HbA1c) levels were higher in DK or DKA (p<0.05). Blood calcium and 25-hydroxyvitamin D3 (25-OH-VitD3) levels were significantly lower in DKA (p<0.05), but parathyroid hormone (PTH) levels remained constant across all three groups. The N-terminal middle molecular fragment of osteocalcin (N-MID) and β-C terminal cross-linking telopeptide of type 1 collagen (β-CTX) showed significant inverse alterations in DKA, regardless of gender or age (p<0.05). Otherwise, DKA significantly inhibited thyroid function (p<0.05). Furthermore, Spearman correlation analyses revealed a relationship between N-MID and HbA1c in DM alone (r=-0.27, p<0.01), while total triiodothyronine (TT3, r=0.62, p<0.01) or free T3 (FT3, r=0.61, p<0.01) in DK, and DKA (TT3, r=0.45, p<0.01; FT3, r=0.43, p<0.01). Multilinear regression analyses revealed that β-CTX (β=0.564), HbA1c (β=-0.196), TT3 (β=0.183), and 25-OH-VitD3 (β=-0.120) were the only independent determinants of N-MID in DM, whereas FT3 (β=0.491), β-CTX (β=0.315) in DK, and FT3 (β=0.420), β-CTX (β=0.367), TG (β=-0.278) in DKA. Only 25-OH-VitD3 was found to be significantly lower in recurrent DK (A) than in single onset DK (A) (p<0.05), and β-CTX (β=0.745) was found to be significantly independently associated with N-MID.

CONCLUSION

Our preliminary findings show a dramatic change in bone turnover markers in DM patients with DK and DKA, and this change may be related to thyroid function.