Epidemiology of Hypothyroidism, Hyperthyroidism and Positive Thyroid Antibodies in the Croatian Population

SIMPLE SUMMARY: The aim of this paper was to analyse the prevalence of hypothyroidism and hyperthyroidism in the Croatian population. This is the first epidemiological study of its kind conducted in our population. It is important to correctly diagnose thyroid dysfunction due to the detrimental effects of thyroid dysfunction on human health (especially in pregnant women and patients with cardiovascular diseases). The results of our study conducted on 4402 individuals, showed a higher prevalence of hypothyroidism in our country (10.5%) compared to other countries, while the prevalence of hyperthyroidism was quite similar (1.3%). We also observed that a high proportion of thyroid disorders remained undiagnosed (as many as 92.6% subclinical hypothyroid, 93.9% clinical hypothyroid, 83% subclinical hyperthyroid and 71.4% clinical hyperthyroid participants). Therefore, our study indicates that investing in prevention programs is crucial. ABSTRACT: Thyroid dysfunction appears to be the leading endocrine disorder. We conducted a cross-sectional study on 4402 individuals from three Croatian cohorts. The aim of this study was to analyse the prevalence of diagnosed and undiagnosed hypothyroidism, hyperthyroidism (subclinical and clinical) and positive thyroid antibodies in the Croatian population. The results of the study indicated that 17.6% of participants were euthyroid with positive antibodies. The prevalence of clinical and subclinical hypothyroidism was 3% and 7.4%, respectively, while the prevalence of clinical and subclinical hyperthyroidism was 0.2% and 1.1%, respectively. Among them, 92.6% subclinical hypothyroid, 93.9% clinical hypothyroid, 83% subclinical hyperthyroid and 71.4% clinical hyperthyroid participants were undiagnosed. Finally, the prevalence of undiagnosed subclinical and clinical hypothyroidism in our population was 6.9% and 2.8%, respectively, while the prevalence of undiagnosed subclinical and clinical hyperthyroidism was 0.9% and 0.1%, respectively. Women showed a higher prevalence of thyroid disorders; 1.57 times higher odds of euthyroidism with positive antibodies, 2.1 times higher odds of subclinical hyperthyroidism, 2.37 times higher odds of clinical hypothyroidism and 1.58 times higher odds of subclinical hypothyroidism than men. These results indicate an extremely high proportion of undiagnosed cases, and therefore require investments in a prevention programme.