Hall SF, et al. - In this population-based study, researchers assessed the Enthusiasm Hypothesis and its applicability to the variation in the surgical treatment of thyroid cancer in Ontario, Canada. The study sample consisted of 28,754 patients who were 18 years of age or older and had an initial therapeutic thyroid surgical procedure for a papillary or follicular carcinoma diagnosis between January 1, 2000, and December 31, 2015. Data reported that the use of total thyroidectomy for differentiated thyroid cancer varied widely across geographic regions of Ontario, from 45.8% to 77.1% of all cases of cancer. The activities of high-volume surgeons (enthusiasts) in regions with the highest rates of a thyroid cancer diagnosis can explain more than 90% of the overall variability in practice (total thyroidectomy vs less-than-total thyroidectomy). The Enthusiasm Hypothesis seems to be consistent with this study's findings. High-volume surgeon's practices that were enthusiastic about total thyroidectomy in geographic regions with the highest rates of diagnosis of thyroid cancer could account for differences in practice across Ontario between 2000 and 2015.