Which of the following is a contraindication for levothyroxine?

Levothyroxine is a synthetic thyroid hormone used primarily to treat hypothyroidism, which is an underactive thyroid condition. In cases of thyrotoxicosis, which refers to an excess of thyroid hormones in the body, the use of levothyroxine would be contraindicated. This is because administering levothyroxine would exacerbate the already high levels of thyroid hormones, potentially leading to severe consequences like heart palpitations, anxiety, and even a thyroid storm, which is a life-threatening condition.

Unlike hypothyroidism, which warrants the use of levothyroxine to restore normal hormone levels, thyrotoxicosis indicates a need for treatments that reduce thyroid hormone levels rather than increase them. Therefore, the presence of thyrotoxicosis makes levothyroxine use inappropriate and potentially harmful.