The relationship between iron deficiency and thyroid function: findings from a population-based study in Jordan

Background This study aimed to examine the association between iron deficiency (ID) and thyroid dysfunction among Jordanian adults.Research Design and Methods A cross-sectional analysis was conducted using data from 3,605 participants in a 2017 nationwide survey covering all 12 Jordanian governorates. Sociodemographic, anthropometric, and biochemical data were collected, including serum ferritin, thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4). Participants were categorized as having iron deficiency (ID), iron deficiency anemia (IDA), or control group (CG). Kruskal – Wallis and chi-square tests were used, with p < 0.05 considered significant.Results Individuals with ID and IDA had significantly lower FT3 and FT4 levels and higher TSH levels compared to CG. The prevalence of hypothyroidism and combined hypothyroidism plus subclinical hypothyroidism was higher in the IDA group (p = 0.0011 and p = 0.0126, respectively). No significant associations were observed for hyperthyroidism or subclinical hyperthyroidism.Conclusion Iron deficiency, particularly IDA, was associated with an increased prevalence of hypothyroidism among Jordanian adults. These findings highlight the importance of thyroid function screening in individuals with low iron status and underline the need for longitudinal studies to clarify causal pathways.