Screening for thyroid disease in women during breast cancer screening is popular in Japan. Some studies concerning screening for thyroid disease have previously been reported in Japan [1,3,4,16,17,23] and other countries [2, 5-15, 18-21, 24] The prevalence of thyroid nodule is reported to be from 1.2 [3] to 35.3% [9], and the prevalence of thyroid cancer is reported to be from 0.08 [12] to 3.9% [20]. Most of these studies primarily included women. The detection rate of thyroid nodule and thyroid cancer has been reported to be higher in women than that in men [3,7,12,14]. Screening for thyroid cancer in men, especially those nearing military retirement aged over 50 and 40 years old has not, to our knowledge, been previously done. We therefore investigated the frequency of thyroid nodules and thyroid cancers in military men at retirement and compared the data to a small number of New evidence about thyroid cancer prevalence: prevalence of thyroid cancer in younger and middle-aged Japanese population There was a significant increase in thyroid nodules in 50 years old men compared to that in 40 year old men, but there was no significant difference between men and women (p>0.05). Our data document that the detection rate of thyroid cancer in 50 years old men was 0.31%, and the rate of thyroid nodules increased with age in men, but the frequency of thyroid nodules were similar in men and women of the same age.Key words: Prevalence of thyroid cancer, Younger and middle-aged Japanese men, Thyroid screening military women who were screened by physical examination and ultrasonography in Japan and in other countries to see whether thyroid nodule and cancer are more common in women than men.
Materials and MethodsSix thousand, four hundred and twenty-two Japanese military men and women were screened with questionnaire, physical examination and ultrasound examination for thyroid disease at the Japanese Self Defense Force Hospital (Central, Hanshin and Kumamoto) from 1990 to 2012. The prevalence of thyroid nodules (excluding pure thyroid cysts) and thyroid cancer was determined. All patients were asymptomatic. Patients with obvious thyroid symptoms were excluded from this database. Among studied patients, 6,182 were men 50 years of age, 47 were women 50 years of age, and 149 were men 40 years of age and 44 were women 40 years of age. No patient had a family history of thyroid cancer or had a past exposure to radiation. We defined "thyroid nodule" as the maximum diameter â„3 mm. We excluded the