Which antibody test can help differentiate between causes of hyperthyroidism?

The thyroid-stimulating hormone (TSH) receptor antibody test is instrumental in differentiating the specific causes of hyperthyroidism, particularly in distinguishing between Graves' disease and other forms of hyperthyroidism. In Graves' disease, these antibodies stimulate the thyroid gland, leading to overproduction of thyroid hormones. The presence of TSH receptor antibodies is characteristic of this condition and helps to confirm the diagnosis.

On the other hand, while TSH levels can indicate hyperthyroidism, they do not differentiate between the underlying causes. Thyroid peroxidase (TPO) antibodies are more relevant in autoimmune thyroid conditions such as Hashimoto's thyroiditis rather than in the context of hyperthyroidism. Antinuclear antibodies (ANA) are indicative of a variety of autoimmune disorders but are not specific to thyroid dysfunction. Thus, the TSH receptor antibody test is crucial for accurately identifying the underlying cause of hyperthyroidism, making it the most relevant choice in this context.