Levothyroxine is commonly used to treat which condition?

Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4) and is primarily used to treat hypothyroidism. In this condition, the thyroid gland does not produce enough thyroid hormones, leading to a variety of health issues such as fatigue, weight gain, and sensitivity to cold. By administering levothyroxine, it helps to restore the normal levels of thyroid hormone in the body, effectively managing the symptoms and improving the patient's overall metabolic state.

In contrast, hyperthyroidism is characterized by excessive production of thyroid hormones and would require medications that inhibit hormone production instead. Conditions like Cushing's disease are related to excess cortisol production, and diabetes mellitus pertains to issues with insulin and blood sugar regulation, neither of which involves the use of levothyroxine. Therefore, the correct association of levothyroxine with the treatment of hypothyroidism is well-founded based on its mechanism of action and therapeutic indications.