What laboratory finding is typically associated with exophthalmos in hyperthyroidism?

Exophthalmos, which refers to the bulging of the eyes, is a characteristic finding in hyperthyroidism, particularly in conditions like Graves' disease. This condition is associated with an overproduction of thyroid hormones, specifically T3 (triiodothyronine) and T4 (thyroxine).

In hyperthyroidism, there is an increased release of these hormones into the bloodstream, which can lead to various metabolic processes being accelerated. As T4 levels rise, they can be detected in laboratory tests, thus explaining the association of increased T4 levels with exophthalmos.

Elevated T4 levels contribute to symptoms such as weight loss, increased appetite, nervousness, and in particular, the characteristic exophthalmos due to the accumulation of glycosaminoglycans behind the eyes, causing swelling and pushing the eyeball forward.

In contrast, decreased or normal T4 levels would not explain the underlying pathology of hyperthyroidism and its associated symptoms, including exophthalmos. Therefore, the presence of increased T4 levels is the correct answer to link with the occurrence of exophthalmos in hyperthyroidism.