Association Between Subclinical Hypothyroidism and the Prognosis of Diabetes Mellitus and Subsequent Complications: A Retrospective Cohort Study.

Background Diabetes mellitus (DM) and subclinical hypothyroidism (SCH) are prevalent metabolic and endocrine disorders. Previous studies have suggested potential associations between SCH and metabolic disorders, including DM. This study aimed to explore the relationship between SCH and DM in patients from the Qassim Region in Saudi Arabia. Methods A retrospective cohort study was conducted on patients who attended the Qassim University clinics from December 2017 to December 2021. Participants were divided into two groups: SCH patients without a history of DM and age- and sex-matched controls without SCH or DM. Parameters, such as DM occurrence, DM duration, glycosylated hemoglobin (HbA1c) values, and metformin use, were evaluated. Results The prevalence of DM was 70.4% in the SCH group and 83.3% in the non-SCH group, with no significant difference between the groups (p=0.203). The mean HbA1c values and DM duration showed no significant variations between the two groups. However, metformin use was significantly higher in the SCH group at 74.1% compared to 50.0% in the non-SCH group (p=0.047). No correlation was observed between HbA1c and thyroid-stimulating hormone (TSH) levels. Conclusions While the study indicates a potential association between SCH and DM management, especially with regard to metformin usage, there does not appear to be a significant relationship between SCH and DM development or progression in this population.