Professional and Linguistic Assessments Board (PLAB) Practice Exam

In underdeveloped countries, what is the most common cause of hypothyroidism?

1. Autoimmune diseases

2. Surgical removal of the thyroid

3. Iodine deficiency

4. Radiation exposure

The correct answer is: Iodine deficiency

In underdeveloped countries, the most common cause of hypothyroidism is iodine deficiency. Iodine is an essential nutrient required for the production of thyroid hormones. When there is insufficient iodine in the diet, the body cannot produce adequate amounts of these hormones, leading to hypothyroidism. Iodine deficiency is particularly prevalent in areas where the soil and water supply lack iodine, which is often the case in underdeveloped regions. As a result, individuals in these areas are at a significantly higher risk for developing hypothyroidism due to the lack of this critical nutrient. In contrast, autoimmune diseases, surgical removal of the thyroid, and radiation exposure are more common causes of hypothyroidism in developed countries or specific clinical contexts rather than the primary concern in underdeveloped nations where iodine is not adequately supplied.