Neuropsychological Impairments in Young Patients With Subclinical Hypothyroidism: A Case Control Study

Association of Hypothyroidism and the Risk of Cognitive Dysfunction: A Meta-Analysis

Objectives: The purpose of this meta-analysis was to assess whether there is an association between hypothyroidism and the risk of cognitive dysfunction. Methods: PubMed, Cochrane Library, and Embase were searched for relevant studies published from database inception to 4 May 2022, using medical subject headings (MeSHs) and keywords. Results: Eight studies involving 1,092,025 individuals were included, published between 2010 and 2021. The pooled analysis showed that there was no association between hypothyroidism and cognitive dysfunction (OR = 1.13, 95% CI = 0.84−1.51, p = 0.426), including both all-cause dementia (OR = 1.04, 95% CI = 0.76−1.43, p = 0.809) and cognitive impairment (OR = 1.50, 95% CI = 0.68−3.35, p = 0.318). Neither overt hypothyroidism (OR = 1.19, 95% CI = 0.70−2.02, p = 0.525) nor subclinical hypothyroidism (OR = 1.04, 95% CI = 0.73−1.48, p = 0.833) was associated with cognitive dysfunction. Neither prospective cohort (OR = 1.08, 95% CI = 0.77−1.51, p = 0.673) nor cross-sectional studies (OR = 1.23, 95% CI = 0.63−2.42, p = 0.545) had any effect on the association. Interestingly, the risk of cognitive dysfunction was significantly increased in the group not adjusted for vascular comorbidity (OR = 1.47, 95% CI = 1.07−2.01, p = 0.017), while it was reduced in the adjusted group (OR =0.82, 95% CI = 0.79−0.85, p < 0.001). Conclusions: This meta-analysis shows that hypothyroidism was associated with a reduced risk of cognitive dysfunction after adjustment for vascular-disease comorbidities. More prospective observational studies are needed in the future to investigate the relationship between hypothyroidism and cognitive dysfunction.

Sex-specific Association of Subclinical Hypothyroidism With Incident Metabolic Syndrome: A Population-based Cohort Study

OBJECTIVE

Subclinical hypothyroidism is known to increase the risk of cardiovascular diseases and mortality. However, the longitudinal association between subclinical hypothyroidism and incident metabolic syndrome remains unclear.

METHODS

A total of 3615 participants from Beijing Health Management Cohort were enrolled from 2012 to 2014 and followed through 2019. People were placed into subclinical hypothyroidism and euthyroidism groups according to serum-free thyroxine and TSH concentrations. We used Cox proportional hazards regression models to investigate the relationship between TSH level and incident metabolic syndrome considering the modification effect of sex and age.

RESULTS

Of 3615 participants, 1929 were men (53.4%); mean (SD) age was 43.51 (11.73) years. Throughout the follow-up (median [interquartile range], 3.0 [2.8-3.2] years), 738 individuals developed metabolic syndrome. Subclinical hypothyroidism was significantly associated with metabolic syndrome development only in men, and the adjusted hazard ratio was 1.87 (95% CI, 1.21-2.90) compared with euthyroidism group. Of note, there was no increased risk of metabolic syndrome in people aged 50 years or older with subclinical hypothyroidism.

CONCLUSIONS

Subclinical hypothyroidism is associated with incident metabolic syndrome in young men. Further studies are needed to evaluate the targeted threshold and benefit of thyroid hormone replacement therapy for metabolic health.