Which hormone secreted by the adrenal medulla has minimal effect on blood sugar levels?

The correct choice is norepinephrine, which is one of the hormones secreted by the adrenal medulla and plays a role in the body's response to stress. While norepinephrine does participate in the fight-or-flight response, it primarily functions to increase heart rate and blood pressure, promoting the body's immediate preparedness for physical activity. Its impact on blood sugar levels is relatively minor compared to other hormones.

Epinephrine, also known as adrenaline, and cortisol are more significant in the context of increasing blood sugar levels. Epinephrine works to facilitate glucose mobilization from glycogen stores in the liver, thereby raising blood sugar levels during stress. Cortisol, a glucocorticoid released from the adrenal cortex rather than the medulla, also has a substantial effect on increasing blood sugar by promoting gluconeogenesis and inhibiting cellular glucose uptake. Adrenaline is merely another term for epinephrine, reinforcing the point about its prominent role in blood glucose regulation.

Thus, norepinephrine, while vital for immediate physiological responses, has a minimal effect on elevating blood sugar levels compared to its counterparts.