Subclinical hypothyroidism and metabolic risk factors association: A health examination-based study in northern Taiwan

Background: Subclinical hypothyroidism (SCH) is defined as elevation in serum thyroid-stimulating hormone (TSH) levels despite normal serum levels of free thyroxine. It remains controversial whether people with SCH have higher total cholesterol and low-density lipoprotein cholesterol levels compared to normal-thyroid subjects. The aim of this study was to assess the metabolic risk factors for SCH. Methods: Subjects were recruited from the health examination center of Chang Gung Memorial Hospital, Linkou, from January 1, 2010 to December 31, 2011. This was a cross-sectional review of medical records. The subjects were ethnic Taiwanese residents without known thyroid disease at baseline. Results: A total of 22,324 subjects received annual health examination at Chang Gung Memorial Hospital from 2010 to 2011. Among them, 15,943 subjects were included as the normal thyroid group (NG), and 203 subjects (101 men and 102 women) met the criteria for SCH. The prevalence of metabolic syndrome (MetS) in the NG was 26.2% in men and 18.7% in women, whereas that in the SCH group was 39.6% in men and 29.4% in women. Women in the SCH group showed significantly higher cholesterol, triglyceride, non-high density lipoprotein (HDL) and cholesterol/HDL levels than those in the NG (p < 0.05) Conclusion: Because SCH is more prevalent in women and the risk increases with age, greater attention to the risk of MetS development is warranted. As for men, regardless of thyroid function, the risk of MetS development with age still warrants attention. Thus, our data suggest that national guidelines for screening for thyroid disease using serum TSH levels in the elderly are mandatory.