Does relatively low iodine intake contribute to thyroid cancer? An ecological comparison of epidemiology

Abstract

Research on the relationship between iodine intake and thyroid cancer (TC) risk is limited, and the findings are inconclusive. The objective of this study was to provide emerging evidence for the association between iodine intake and TC risk in a Chinese population.An ecological study of epidemiology is used to compare the iodine intake among populations with different TC incidence in Zhoushan, China. Incidence rates of TC were investigated and compared among four counties of the Zhoushan Islands from 2014 to 2018. Iodized salt consumption rate and the level of urinary iodine concentration (UIC) were analyzed for pupils and pregnant women from four counties.During 2014 to 2018, a total of 2495 new cases of TC were diagnosed in Zhoushan Islands. The mean crude incidence rate of TC was 51.29 per 100,000 inhabitants, and the standardized (world population) incidence rate (SIR) was 31.34 per 100,000 population. Incidence rates (SIR and crude incidence rates) were significantly higher in women than in men (χ2 test, P < .05). Both male and female, the incidence of TC in Daishan County is higher than the other three counties of Zhoushan. Iodized salt consumption rate and median UIC in pupils and pregnant women in Daishan County was significantly lower than the other three counties (χ2 test and Kruskal–Wallis test, all P < .05). The population with high TC incidence has a lower iodized salt consumption and a lower level of UIC compare with the relative low TC incidence populations.The low consumption of iodized salt with mild iodine deficiency may contribute to explain the exceptionally high incidence of TC in Daishan County. Further subtle designed studies are needed to provide additional insights into the epidemiology and etiology of TC and help identify the safe limit of iodine intake for prevention.

Association between excessive chronic iodine exposure and the occurrence of papillary thyroid carcinoma

“…Furthermore, Santos et al (14) used reservoir water iodine content combined with UIC to evaluate chronic iodine exposure in thyroid histology pattern research. Zhang et al (15) investigated iodized salt consumption combined with UIC to estimate long-term iodine intake. However, this ecology-based integrated assessment design of iodine exposure (which utilized water iodine or iodized salt consumption combined with the UIC) is rarely applied for the analysis of clinicopathological characteristics in PTC.…”

Insufficient iodine nutrition may affect the thyroid cancer incidence in China

“…Cardis's study showed that the risk of radiation-related thyroid cancer was 3-fold higher in iodine-deficient areas than elsewhere and that administration of potassium iodide as a dietary supplement reduced the risk of radiation-related thyroid cancer (25) . A study in Zhoushan, China, also showed that the population with a high thyroid cancer incidence had a lower iodised salt consumption and a lower UIC than populations with a relatively low thyroid cancer incidence (26) . Similarly, in our study, it is also found that Daishan County, which is located in Zhoushan, had a low CRQIS (20-70 %) in recent years (27,28) and had a high incidence of thyroid cancer.…”

Epidemiología del cáncer de tiroides en un Instituto Oncológico. Efecto de las nuevas recomendaciones clínicas

“…Es importante establecer que factores de riesgo explican la alta y creciente incidencia de CT en nuestro país. En los últimos años se han asociado con mayor riesgo de CT, además de la exposición a radiación, la obesidad, el sedentarismo y la diabetes mellitus 2 [19][20][21] , contaminantes químicos como bisfenol A y cadmio 21,22 , la baja ingesta de yodo y la ingesta excesiva de nitritos 24,25 y factores reproductivos en la mujer 26 .…”