Which of the following characteristics is most commonly associated with Graves' disease?

Graves' disease is an autoimmune disorder that is the most common cause of hyperthyroidism, characterized by the overproduction of thyroid hormones. One of the hallmark features of Graves' disease is the presence of a goiter, which is an enlargement of the thyroid gland. This occurs due to the overstimulation of the gland by thyroid-stimulating immunoglobulins that mimic thyroid-stimulating hormone (TSH). Consequently, the thyroid gland enlarges as it produces excessive amounts of thyroid hormones.

In contrast, hypothyroidism, weight gain, and palpitations, while they may occur in different contexts within thyroid disorders, are not characteristic features of Graves' disease itself. Typically, hypothyroidism is associated with conditions that reduce thyroid hormone production, which would not align with the hyperthyroid state seen in Graves'. Weight gain is more commonly associated with hypothyroidism rather than hyperthyroidism, and while palpitations can occur due to the effects of excessive thyroid hormones, they are more symptomatic of the hyperthyroid state rather than a defining characteristic of Graves' disease itself. The most defining and common characteristic of Graves' disease, therefore, remains the presence of a goiter.