Which of the following hormones is secreted by the adrenal gland?

Cortisol is a hormone produced by the adrenal glands, specifically within the adrenal cortex. It plays a crucial role in glucose metabolism, stress response, and immune function regulation. Cortisol is often referred to as the "stress hormone" because its levels increase in response to stress and low blood glucose levels. It helps to mobilize energy by increasing glucose availability, suppressing the immune system, and aiding in the metabolism of fats, proteins, and carbohydrates.

In contrast, insulin is a hormone secreted by the pancreas, which is responsible for regulating blood glucose levels. Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), are produced by the thyroid gland and are key regulators of metabolism. Renin is an enzyme released by the kidneys, not the adrenal glands, and it plays a role in the regulation of blood pressure.

Thus, cortisol is the only hormone listed that is secreted by the adrenal gland, making it the correct answer to the question.