Which of the following conditions is characterized by fatigue, lethargy, and cold intolerance?

The condition characterized by fatigue, lethargy, and cold intolerance is Hashimoto's thyroiditis. This autoimmune disorder affects the thyroid gland, leading to hypothyroidism. In hypothyroidism, there is a decrease in the production of thyroid hormones, which are crucial for regulating metabolism and energy levels in the body.

When thyroid hormone levels are low, individuals often experience symptoms like fatigue and lethargy because the body's metabolic processes slow down. Cold intolerance also arises due to reduced metabolic heat production; people with low thyroid hormone levels may have difficulty maintaining body temperature in cold environments.

In contrast, Graves' disease, primary hyperthyroidism, and toxic goiter involve excessive production of thyroid hormones, leading to symptoms such as weight loss, increased heart rate, nervousness, and heat intolerance, which are opposite of what is presented in Hashimoto's thyroiditis. Thus, the symptoms outlined in the question align specifically with the characteristics of Hashimoto's thyroiditis.