Insufficient dietary iodine can lead to several health problems, but the specific effect mentioned in the correct answer is an enlarged thyroid, or goiter. The thyroid gland requires iodine to produce thyroid hormones, which play a crucial role in regulating metabolism. When the body doesn`t obtain enough iodine from the diet, the thyroid gland attempts to compensate by growing larger to trap more iodine. This results in a visibly enlarged thyroid gland, which is known as a goiter. Cretinism, mentioned in option 1, is a condition caused by severe iodine deficiency during infancy and childhood, leading to stunted growth and intellectual disabilities. While not mentioned in the answer options, insufficient iodine intake can also lead to other health issues such as hypothyroidism and impaired cognitive development in children.