Step 1: Understanding the Concept
Cortisol is the main glucocorticoid of the adrenal cortex.
Step 2: True statements
It regulates protein, fat and carbohydrate metabolism, suppresses immune responses, and helps the body face emergencies and stress.
Step 3: The wrong statement
Cortisol promotes gluconeogenesis and reduces glucose uptake by cells, so blood glucose rises. It does not decrease it.
Final Answer:
The incorrect statement is that cortisol decreases blood glucose.
\[ \boxed{\text{(C) }\text{It causes decrease in blood glucose level}} \]