Cancer gender disparity in incidence, disease aggressiveness and prognosis has been observed in a variety of cancers. Thyroid cancer is one of the fastest growing cancer diagnoses worldwide. It is 2.9-times more common in women than men. The less aggressive histologic subtypes of thyroid cancer are more common in women, whereas the more aggressive histologic subtypes have similar gender distribution. The gender disparity in incidence, aggressiveness and prognosis is well established for thyroid cancer but the cause of the disparity is poorly understood. The aim of this article is to evaluate the current evidence on the cause of thyroid cancer gender disparity. Dietary and environmental factors do not appear to have a significant role in thyroid cancer gender disparity. Common somatic mutations in BRAF, rearranged in transformation/papillary thyroid carcinomas (RET/PTC) and neurotrophin receptor-tyrosine kinase (NTRK) also do not account for the gender disparity in thyroid cancer. While reproductive factors would seem a logical hypothesis to account for the gender disparity, there appears to be no conclusive effect on the risk of developing thyroid cancer. Recent studies on estrogen receptor status in thyroid cancer show a difference in the receptor subtypes expressed based on the histology of thyroid cancer. Moreover, the response to estrogen is dependent on the specific estrogen receptor expressed in thyroid cancer cells. However, what determines the tumor-specific sex hormone receptor expression is unclear. No established molecular factors appear to explain gender differences in thyroid cancer. Therefore, the application of high-throughput genomic and proteomic approaches to the study of thyroid cancer gender disparity could be helpful for better understanding the molecular basis for gender differences in thyroid and other cancers.