What condition does levothyroxine primarily treat?

Levothyroxine is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones. These hormones are crucial for regulating metabolism, energy production, and overall growth and development in the body. By providing a synthetic form of thyroxine (T4), levothyroxine helps to restore hormone levels to normal, alleviating symptoms associated with hypothyroidism such as fatigue, weight gain, and depression.

In contrast, hyperthyroidism, which involves an overproduction of thyroid hormones, requires a different treatment approach, often including antithyroid medications or radioactive iodine. Cancer and diabetes are unrelated to thyroid hormone levels. Thus, levothyroxine's role is specifically aligned with managing hypothyroidism, making it the correct choice.