Women with elevated body mass index (BMI) and hypertension may benefit from regular screening for subclinical hypothyroidism (SCH), according to study results published in BMC Endocrine Disorders.
Metabolic syndrome components have been linked to SCH, but age, sex, and BMI may affect these associations. To examine the relationship between metabolic risk factors, sex, and subclinical thyroid dysfunction in a large Chinese population, researchers collected and analyzed data from 5319 patients aged ≥20 years (mean age, 42.53 years) who underwent a health examination at Ningbo Medical Center Lihuili Hospital in Ningbo, China, between June 2016 and April 2018.
Individuals were divided into 2 groups based on serum concentrations of thyrotropin (TSH) and free thyroxine levels: euthyroid or SCH (TSH level, 5.0-10.0 µIU/mL). Patients who had a TSH level >10.0 µIU/mL were excluded.
There were 181 cases of SCH in the overall population (3.40% prevalence), with a higher prevalence among women than men (4.90% vs 2.26%, respectively; P <.001). This trend was consistent across all age categories, with the largest difference observed between men and women aged 50 to 59 years. In addition, women aged <40 years were significantly less likely to have SCH compared with older women (P =.023), but there was no significant difference in SCH prevalence among men aged <60 vs ≥60 years.
In multivariate logistic regression analysis, age (odds ratio [OR], 0.568; 95% CI, 0.389-0.831; P <.004), systolic and diastolic blood pressure (OR, 2.543, 95% CI, 1.709-3.784; P <.001), and BMI (OR, 5.029; 95% CI, 3.306-7.6511; P <.001) were all independent predictors of SCH in women. In an analysis comparing groups of women with high or low blood pressure and BMI, rates of SCH were significantly higher in those with hypertension and elevated BMI, regardless of age (P <.001). No metabolic risk factors were related to SCH prevalence in men.
As the study was cross-sectional, the researchers could not determine the longitudinal effects of elevated BMI and blood pressure on SCH, nor explore the underlying mechanisms between these associations.
“In our study, as many as 9.04% of female participants who had at least one above metabolic risk factor were finally diagnosed with SCH, which suggested that TSH screening may be a suitable option for women with high [blood pressure] and/or high BMI… [T]hese women may eventually develop to overt hypothyroidism each year at a rate of [4.3% to 8.0%],” stated the study authors.
Jiang L, Du J, Wu W, Fang J, Wang J, Ding J. Sex differences in subclinical hypothyroidism and associations with metabolic risk factors: a health examination-based study in mainland China. BMC Endocr Disord. 2020;20(1):100.