Hypertension and subclinical hypothyroidism : a cross-sectional survey based on population in Gansu Province
Authors: Liu Qianqian , Chang Xingyu , Wang Yaqi , Fu Songbo , Tang Xulei , Jing Gaojing , Niu Qianglong , Teng Weiping 
Published: November 2022

Abstract
Purpose:To investigate the prevalence and related influencing factors of subclinical hypothyroidism (SCH) in patients with hypertension (HTN).
Patients and Methods:The 2,818 adult residents in Gansu Province were selected by the multi-stage stratified cluster random sampling method, and the prevalence of standardization was calculated using the direct mapping method. General data and related biochemical indexes were recorded to analyze the prevalence of HTN and SCH. The HTN population was divided into grade 1 HTN, grade 2 HTN and grade 3 HTN groups. The χ2 test was used to analyze the differences in the prevalence of HTN and SCH in age, sex and thyroid antibody levels. The Logistic regression analysis model was used to analyze the risk factors for SCH in the HTN population.
Results:A total of 2,818 study subjects were included, with 591 SCH patients and 604 HTN patients. The prevalence of SCH was higher in HTN populations under 60 years than in normotensive population (28.95% vs 17.58%, χ2=21.180, P < 0.05).In this study, we found that whether considering the physiological increase of TSH level in the elderly(using higher TSH cut-offs for people over 65 years) has a greater impact on the prevalence of SCH in the elderly population. We compared and analyzed the two situations. Excluding the physiological increase of TSH levels in the elderly, the prevalence of SCH in the HTN population is higher than that in the normal population (χ2=40.039, P< 0.05).Considering this effect (using higher TSH cut-offs for people over 65 years), the prevalence of SCH decreased significantly (from 28.00% to 4.00% in normal blood pressure population, from 28.89% to 6.67% in high-normal blood pressure population, and from 34.73% to 7.19% in HTN population, all P＜0.05).The prevalence of SCH was higher in the HTN population, whether or not considering the effect of age on TSH, than in the normal blood pressure population (24.34% vs 17.28%, χ2=11.813;31.95% vs 17.86%, χ2 =40.039,both P<0.05). Moreover, the prevalence of SCH between normal blood pressure,high-normal blood pressure and HTN population were significantly different(P < 0.05). In the HTN population, the DBP, TC, TSH, blood phosphorus, TPOAb, and TgAb levels were higher in the SCH group than in the normal group（P < 0.05). The TPOAb and TgAb levels were higher in women in the SCH population than in men (P < 0.05).Considering the physiological increase of TSH levels in the elderly, the prevalence of SCH in the total HTN population and grade 2 population with SCH was higher than in thyroid antibody negative patients（35.90% vs 22.62%, P<0.05).The Logistic regression analysis showed that the risk factors for SCH in the HTN population were FPG, TG, LDL-C, TPOAb, and TgAb, and the protective factor was heart rate (P < 0.05).
Conclusion: The prevalence of SCH in the HTN population was relatively high and was significant in female population. The authenticity of SCH in the elderly population caused by the physiological increase of age-related TSH needs to attract more attention. The HTN population should be careful to monitor the correlation of their own glucose metabolism levels and TSH.