Abstract
BackgroundThyroid cancer incidence rates have been increasing worldwide but the reason behind this is unclear. Both the increasing use of diagnostic technologies allowing the detection of thyroid cancer and a true increase in thyroid cancer incidence have been proposed. This review assesses the role of body mass index (BMI), diet, and reproductive factors on the thyroid cancer trend.MethodsEpidemiologic studies of the selected risk factors up to June 2010 were reviewed and critically assessed.ResultsAmong the thirty-seven studies reviewed and despite variation in the risk estimates, most papers supported a small but positive association for BMI (risk estimate range: 1.1–2.3 in males and 1.0–7.4 in females.). Among specific dietary components, there was no consistent association of thyroid cancer risk with iodine intake through fortification (risk estimate range: 0.49–1.6) or fish consumption (risk estimate range 0.6–2.2), nor with diets high in cruciferous vegetables (risk estimate range 0.6–1.9). A small number of studies showed a consistent protective effect of diets high in non-cruciferous vegetable (risk estimate range: 0.71–0.92). Among reproductive factors (pregnancy, parity, number of live births, use of prescription hormones, menstrual cycle regularity, and menopausal status), none were consistently associated with higher thyroid cancer risk.ConclusionsBMI had the strongest link to thyroid cancer risk among those examined. Detailed examinations of population-level risk factors can help identify and support prevention efforts to reduce the burden of thyroid cancer.
Highlights
Over the past 30 years many countries have experienced a dramatic rise in the incidence of thyroid cancer, with a study across five continents showing the average increase to be 67% in females and 48% in males between 1973 and 2002 [1]
The increase in thyroid cancer incidence is mainly associated with papillary carcinoma, with smaller increases occurring in other types such as follicular carcinoma [3,4,5]
From an initial list of 6677 potentially relevant studies, 37 studies on body mass index (BMI), diet and reproductive history were retained for review
Summary
Over the past 30 years many countries have experienced a dramatic rise in the incidence of thyroid cancer, with a study across five continents showing the average increase to be 67% in females and 48% in males between 1973 and 2002 [1]. The increase in thyroid cancer incidence is mainly associated with papillary carcinoma, with smaller increases occurring in other types such as follicular carcinoma [3,4,5]. The incidence of thyroid cancer is higher in women than men with a consistent ratio of 3:1, except for in the adolescent and young adult age group where the incidence in females is as much as 5-fold higher [8]. Thyroid cancer incidence rates have been increasing worldwide but the reason behind this is unclear. This review assesses the role of body mass index (BMI), diet, and reproductive factors on the thyroid cancer trend
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