The most common cause of goitrous hypothyroidism in adults is:

C. Hashimoto's disease

DISCUSSION: Hashimoto's disease was first described in Japan by Hakaru Hashimoto in 1912 and is the best-known of the immunologic thyroid diseases. It is the most common cause of goitrous hypothyroidism in adults and of sporadic goiter in children. The incidence is 0.3 to 1.5 cases per 1000 population per year and it is 10 to 15 times more common in women than in men, with the highest incidence in the group aged 30 to 50 years.