Which of the following is a common treatment for type 2 diabetes?

Metformin is widely recognized as a first-line treatment for type 2 diabetes due to its effectiveness in lowering blood glucose levels and its favorable safety profile. It works primarily by decreasing hepatic glucose production and improving insulin sensitivity in muscle and adipose tissues. This leads to better utilization of glucose and helps manage blood sugar levels without causing significant weight gain, making it particularly suitable for overweight or obese patients often seen in type 2 diabetes.

In contrast, while insulin may be used in type 2 diabetes, it's generally reserved for cases where blood glucose cannot be controlled by other means, as it can lead to weight gain and has a higher risk of causing hypoglycemia. Thyroid hormone and glucagon are not utilized in the management of type 2 diabetes directly. Thyroid hormone treats conditions related to low thyroid function, while glucagon is primarily used to treat severe hypoglycemia and is not a standard treatment for diabetes itself.