Epidemiological Patterns and Determinants of Subclinical and Overt Hypothyroidism in a Clinical Cohort from the Hail Region, Saudi Arabia: A Retrospective Cross-Sectional and Cluster Analysis Study

Background: Hypothyroidism is a globally prevalent disorder with variations in its occurrence. However, few studies have reported its prevalence in Saudi Arabia. This study aimed to establish the prevalence, characteristics, and predictors of subclinical and overt hypothyroidism in a clinical cohort from the Hail region of Saudi Arabia. Methods: A retrospective cross-sectional design was used. Electronic medical records of adults (aged ≥18 years) who underwent thyroid function testing (TSH, FT4, and FT3) at the study institution were reviewed. Participants with missing laboratory or demographic data and those with hyperthyroidism (TSH < 0.4 mIU/L) were excluded. Hypothyroidism was classified biochemically using internationally accepted TSH and FT4 thresholds. The final analysis cohort comprised 724 participants. Results: Of 724 participants, 471 (65.1%) were euthyroid, 234 (32.3%) had subclinical hypothyroidism, and 19 (2.6%) had overt hypothyroidism, yielding a total biochemical hypothyroidism prevalence of 34.9% (n = 253). Women were over-represented (89.6%), and obesity was prevalent (69%). The biochemical results confirmed that overt hypothyroidism showed significantly elevated TSH and decreased FT4 compared to subclinical hypothyroidism. There were non-significant associations between gender, BMI, and hypertension with thyroid status. Age was an independent predictor of hypothyroid status (OR = 0.983, 95% CI: 0.970–0.995, p = 0.008), and systolic blood pressure was also independently associated (OR = 1.011, 95% CI: 1.002–1.019, p = 0.016). Multiple regression showed age, hypertension, gonarthrosis, and chest pain were independently associated with TSH levels. Hierarchical clustering suggested potential regional patterns in hypothyroidism prevalence. Conclusions: Hypothyroidism, mostly subclinical, was prevalent in this clinical cohort. Age and systolic blood pressure were independent predictors, while BMI and gender were not. Biochemical assessment is essential for detection, and larger prospective studies are recommended.