Establishment of Reference Intervals for Thyroid-Associated Hormones Using refineR Algorithm in Chinese Population at High-Altitude Areas

Effects of altitude on thyroid disorders according to Chinese three-rung, ladder-like topography: national cross-sectional study

BACKGROUND

Chinese topography appears a three-rung ladder-like distribution of decreasing elevation from northwest to southeast, which is divided by two sloping edges. Previous studies have reported that prevalence of thyroid diseases differed by altitude, and geographical factors were associated with thyroid disorders. To explore the association between three-rung ladder-like regions and thyroid disorders according to unique Chinese topographic features, we conducted an epidemiological cross-sectional study from 2015-2017 that covered all 31 mainland Chinese provinces.

METHODS

A total of 78,470 participants aged ≥ 18 years from a nationally representative cross-sectional study were included. Serum thyroid peroxidase antibody, thyroglobulin antibody, and thyroid-stimulating hormone levels; urine iodine concentration; and thyroid volume were measured. The three-rung ladder-like distribution of decreasing elevation from northwest to southeast in China was categorized into three topographic groups according to elevation: first ladder, > 3000 m above sea level; second ladder, descending from 3000-500 m; and third ladder, descending from 500 m to sea level. The third ladder was further divided into groups A (500-100 m) and B (< 100 m). Associations between geographic factors and thyroid disorders were assessed using linear and binary logistic regression analyses.

RESULTS

Participants in the first ladder group were associated with lower thyroid peroxidase (β = -4.69; P = 0.00), thyroglobulin antibody levels (β = -11.08; P = 0.01), and the largest thyroid volume (β = 1.74; P = 0.00), compared with the other groups. The second ladder group was associated with autoimmune thyroiditis (odds ratio = 1.30, 95% confidence interval [1.18-1.43]) and subclinical hypothyroidism (odds ratio = 0.61, 95%confidence interval [0.57-0.66]) (P < 0.05) compared with the first ladder group. Group A (third ladder) (500-100 m) was associated with thyroid nodules and subclinical hypothyroidism (P < 0.05). Furthermore, group B (< 100 m) was positively associated with autoimmune thyroiditis, thyroid peroxidase and thyroglobulin antibody positivity, and negatively associated with overt hypothyroidism, subclinical hypothyroidism, and goiter compared with the first ladder group(P < 0.05).

CONCLUSION

We are the first to investigate the association between different ladder regions and thyroid disorders according to unique Chinese topographic features. The prevalence of thyroid disorders varied among the three-rung ladder-like topography groups in China, with the exception of overt hyperthyroidism.

[A multi-center analysis of thyroid-stimulating hormone level in apparently healthy elderly population in China]

OBJECTIVE

To investigate serum thyroid stimulating hormone (TSH) level and its changes with age in apparently healthy Chinese elderly population and analyze the differences between TSH levels detected using Roche and Snibe electrochemiluminescence immunoassay analyzers.

METHODS

General clinical data and frozen fasting serum samples were collected from 5451 apparently healthy Chinese elderly individuals (> 60 years) from 10 centers in different geographic regions in China. Thyroid function indexes including TSH level were detected using Roche and Snibe electrochemiluminescence immunoassay analyzer, and the median (2.5% and 97.5% quantiles) TSH level was calculated. The variations of TSH level among the participants with geographic regions, gender, and age (with an interval of 5 years) were analyzed to determine the influence of these factors on TSH level.

RESULTS

The reference ranges of serum TSH level established using Roche and Snibe electrochemiluminescence immunoassay analyzers were 0.42-9.47 mU/L and 0.36-7.98 mU/L, respectively, showing significant differences between the two methods (P < 0.001). The TSH levels measured at two centers in Western China were significantly higher than those at the other centers (P < 0.05). In elderly male population, serum TSH level tended to increase with age, which was not observed in elderly female population. At the age of 60-75 years, women generally had higher serum TSH level than men, but this difference was not observed in the population beyond 75 years.

CONCLUSION

In elderly population, serum TSH level can vary with geographic region, gender, and age, but there was no need for establishing specific reference ranges for these factors. The differences between different detection methods should be evaluated when interpreting the detection results of TSH level.

Age-specific serum thyrotropin reference range for the diagnosis of subclinical hypothyroidism and its association with lipid profiles in the elderly population

The overdiagnosis of subclinical hypothyroidism (SCH) in the elderly has driven researchers to establish age-specific thyroid stimulating hormone (TSH) intervals to precisely evaluate the prevalence of SCH. Moreover, abnormal lipid profiles, an insidious manifestation of SCH, show various impacts on different age groups. This study aimed to establish an age-specific TSH reference range to clarify the spectrum of SCH in the elderly. The prevalence of dyslipidemia and the age-specific association between TSH and lipid profiles were analyzed to elucidate the relationship between SCH and dyslipidemia. This cross-sectional study enrolled 2460 participants aged ≥ 65 years via cluster sampling. All participants received physical, laboratory tests and thyroid ultrasound examination and completed the questionnaire. The chi-square test was used to analyze variations of dyslipidemia prevalence among different groups. The Cochran-Armitage trend test was applied for testing the linear trends of age-specific prevalence of dyslipidemia among different TSH intervals in each age group. After adjusting for confounding factors, the age-specific association between TSH and lipid profiles was identified using multi-variate linear regression analysis. The TSH reference ranges in the 65-70 age group, 71-80 age group and > 80 age group were 0.65-5.51 mIU/L, 0.85-5.89 mIU/L and 0.78-6.70 mIU/L, respectively. Using these age-specific reference ranges, the prevalence of SCH in the whole population was 3.74%, which was significantly lower than the prevalence based on the laboratory reference range (10.28%). In the 65-70 age group, only the prevalence of high total cholesterol (TC) increased significantly with the age-specific TSH intervals, and TSH was positively associated with TC and low-density lipoprotein cholesterol (LDL-C). In the 71-80 and > 80 age groups, the prevalence of high TC, high triglycerides (TGs), and high LDL-C increased significantly with elevated TSH reference ranges. The levels of TC, TGs, and LDL-C were also positively associated with TSH level in 71-80 age group. However, such an association disappeared in > 80 age group. An age-specific reference range for TSH can effectively prevent the overdiagnosis of SCH in the elderly. Aging could somewhat attenuate the impact of TSH on lipid profiles.