Levothyroxine is used to treat:

Choice A rationale

Levothyroxine is a synthetic form of thyroxine (T4). It is the standard treatment for hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. The medication replaces the deficient hormone, restoring normal metabolic function in the body.

Choice B rationale

Levothyroxine is a thyroid hormone replacement, so it would worsen hyperthyroidism, a condition characterized by an overproduction of thyroid hormones. The treatment for hyperthyroidism involves anti-thyroid medications, radioactive iodine, or surgery to reduce hormone levels.

Choice C rationale

While levothyroxine is sometimes used after thyroid cancer surgery to suppress TSH (thyroid-stimulating hormone) and prevent the recurrence of cancer, its primary and most common use is to treat the resulting hypothyroidism, not the cancer itself.

Choice D rationale

Thyroiditis is inflammation of the thyroid gland. While it can cause temporary hyperthyroidism or hypothyroidism, levothyroxine is only used to treat the resulting hypothyroidism after the inflammatory phase has passed, not the inflammation itself.

Choice A rationale

Metformin, a biguanide, does not increase insulin secretion from the pancreas. Instead, it works independently of insulin secretion and is often used in patients with type 2 diabetes who still produce their own insulin, which is why it has a low risk of causing hypoglycemia.

Choice B rationale

Metformin's primary mechanism of action is to decrease the production of glucose by the liver, a process known as hepatic gluconeogenesis. By reducing this overproduction of glucose, it helps to lower elevated blood glucose levels in patients with type 2 diabetes.

Choice C rationale

Metformin does not increase carbohydrate absorption from the gastrointestinal tract. In fact, it has been shown to slightly decrease glucose absorption, which contributes to its overall glucose-lowering effect and may also be responsible for some of its gastrointestinal side effects.

Choice D rationale

While metformin does modestly increase insulin sensitivity in peripheral tissues, its primary and most significant effect is the reduction of hepatic glucose production. This is the main mechanism by which it lowers blood sugar, making it a cornerstone of type 2 diabetes treatment.