Which hormone primarily acts to increase blood sugar levels?

Cortisol is a glucocorticoid hormone produced by the adrenal cortex, and it plays a critical role in the body's response to stress. One of its primary functions is to increase blood sugar levels through several mechanisms. It promotes gluconeogenesis, which is the process by which the liver converts non-carbohydrate sources, such as amino acids and glycerol, into glucose. Additionally, cortisol reduces the uptake of glucose by peripheral tissues, ensuring that more glucose remains available in the bloodstream. This action is especially important during stress or fasting situations, where the body requires an increased supply of energy.

While other hormones such as epinephrine and norepinephrine do influence blood sugar levels by stimulating glycogen breakdown in the liver, their primary roles are more associated with the "fight or flight" response rather than the sustained regulation of blood glucose. Aldosterone primarily regulates electrolyte balance and fluid retention rather than directly affecting blood sugar levels, making cortisol the primary hormone among the listed options that acts to elevate blood sugar levels.