A lack of iodine in the diet may lead to which disorder?

A lack of iodine in the diet is primarily associated with the development of goitre, which is the correct choice. Iodine is an essential nutrient required for the synthesis of thyroid hormones, which play a critical role in regulating metabolism, growth, and development. When there is insufficient iodine, the thyroid gland is unable to produce adequate amounts of these hormones.

As a compensatory mechanism, the thyroid gland often enlarges in an attempt to capture more iodine from the bloodstream, leading to the characteristic swelling known as goitre. This condition is particularly prevalent in regions where iodine is deficient in the soil and food supply.

The other choices involve different mechanisms or conditions unrelated to iodine deficiency. For example, hypothyroidism can result from other factors but is not directly caused solely by a lack of iodine. Diabetes mellitus is a metabolic disorder related to insulin and blood sugar levels, and hyperthyroidism is characterized by an overproduction of thyroid hormones, which is the opposite of what occurs in cases of iodine deficiency. Thus, iodine deficiency specifically leads to goitre due to the thyroid gland's response to the lack of hormone production.