What is the most likely diagnosis for a patient exhibiting fatigue, cold intolerance, and a nodular thyroid gland?

The symptoms of fatigue, cold intolerance, and the presence of a nodular thyroid gland strongly suggest chronic autoimmune thyroiditis, also known as Hashimoto's thyroiditis. This condition is characterized by the immune system mistakenly attacking the thyroid gland, leading to inflammation and hypothyroidism. The nodular appearance is often due to the formation of lymphocytic infiltrates and fibrosis as the disease progresses.

Cold intolerance is commonly associated with hypothyroidism, as the thyroid hormone plays a critical role in thermoregulation and metabolism. Fatigue is another prevalent symptom due to the decrease in metabolic activity resulting from low thyroid hormone levels.

While other conditions such as granulomatous thyroiditis and papillary carcinoma can lead to thyroid enlargement and nodules, they typically do not present with the same systemic symptoms of fatigue and cold intolerance. Toxic multinodular goiter usually causes hyperthyroid symptoms rather than those associated with hypothyroidism, such as the ones outlined in this case.

Overall, the combination of these symptoms and the nodular thyroid gland clearly points to chronic autoimmune thyroiditis as the most likely diagnosis.