Geographical influences on thyroid abnormalities in adult population from iodine-replete regions: a cross-sectional study

Abstract

The studies on the increasing incidence of thyroid abnormalities are scarce. The aim of this current study was to ascertain the effects of geographical region on thyroid abnormalities under the context of universal salt iodization (USI). We randomly selected 1255 participants residing in inland and 1248 in coast, with the determination of urinary iodine concentration (UIC) and functional and morphological abnormalities of thyroid gland. The median UIC was significantly higher for the inland participants (188.5 μg/L) than the coastal participants (128.5 μg/L; p < 0.001), indicating iodine sufficiency in both populations according to the recommended assessment criteria by the World Health Organization. However, the spectrum of thyroid abnormalities varied between regions, with hypothyroidism prevalent in inland and thyroid nodules in coast. The associations between region and thyroid abnormalities via binary logistic regression models showed that the coastal participants were at a higher risk of total thyroid abnormalities than those from the inland (OR 1.216, 95% CI 1.020–1.449), after the adjustment of ten confounders (demographical characteristics, smoking status, metabolism syndrome, and hyperuricemia). These results indicated that further investigations of the adverse effects of hypothyroidism and thyroid nodules on health burden is urgently needed to sustain USI program.

Prevalence and risk factors of hypothyroidism after universal salt iodisation: a large cross-sectional study from 31 provinces of China

“…The percentage of hypothyroidism was significantly higher for the participants from the inland (17.5%) than those from the coast (7.2%; p < 0.001). 38 A survey in Shanghai, China, yielded similar results. 39 We also found this phenomenon for both OH and SCH.…”

“…Another study in China found the median UIC for the participants from the inland (188.5 µg/L) was significantly higher than those from the coast (128.5 µg/L; p < 0.001). The percentage of hypothyroidism was significantly higher for the participants from the inland (17.5%) than those from the coast (7.2%; p < 0.001) 38. A survey in Shanghai, China, yielded similar results 39.…”

Thyroid function and epilepsy: a two-sample Mendelian randomization study

“…Subclinical and overt thyroid dysfunction are common diseases of the endocrine system. The incidence rates vary across different regions, with the coastal population having a higher risk of developing thyroid abnormalities compared to inland areas ( Wang et al, 2021 ). Genetic susceptibility is closely associated with the onset of thyroid diseases, such as autoimmune thyroid diseases (AITD) ( Medici et al, 2014 ).…”

Iodine intake assessment in the staff of a Porto region university (Portugal): the iMC Salt trial

“…Moreover, the study population was not nationally representative, since participants were primarily recruited among the university staff, mainly from coastal urban areas, with a high level of education, and included fewer smokers than the general population. Regional divergence, with proximity to the coastal zone and rural areas associated with the iodine status, has been reported, including in Portugal [ 6 , 7 , 62 , 63 ]. Also, participants with a higher level of education were more likely to have better socio-economic status and therefore be more prone to a healthy diet.…”