Higher Prevalence of Subclinical Hypothyroidism in Croatian War Veterans: A Cross-Sectional Study

Background/Objectives: Long-term thyroid function in war veterans remains insufficiently characterized. This study examined the prevalence of thyroid dysfunction in Croatian Homeland War veterans compared to controls. Methods: Cross-sectional study comparing 337 male veterans (mean age 62.4 years) with 335 age-comparable male controls (mean age 61.7 years). Thyroid function was assessed via TSH and FT4. The main outcome of interest was the prevalence of subclinical hypothyroidism (TSH over 4.0 mIU/L with normal FT4). Results: Subclinical hypothyroidism was more prevalent in veterans (12.5%, 42/335) than controls (5.2%, 16/305; OR = 2.59, 95% CI: 1.42–4.71, p = 0.001). After adjustment for age and BMI, the association remained significant (adjusted OR = 2.25, 95% CI: 1.19–4.23, p = 0.012). Mean TSH was modestly higher in veterans (2.53 ± 1.47 vs. 2.06 ± 1.10 mIU/L, p = 0.001), with both groups’ mean values within the normal reference range. Other biochemical parameters showed no significant differences. Conclusions: Veterans showed a higher prevalence of subclinical hypothyroidism compared to controls. The clinical significance of this finding requires further investigation, as mean TSH values remained within normal limits in both groups. The cross-sectional design precludes causal inference, and unmeasured confounders may contribute to the observed association.