Cortisol is released in response to prolonged stresses; one situation when cortisol is released is when blood glucose level is low. In this situation cortisol acts on adipose tissue promoting fatty acid mobilization, and also promotes gluconeogenesis by degrading muscle proteins and converting them into pyruvate. Cortisol also stimulates gluconeogenesis by increasing the expression of PEP Carboxykinase the enzyme of gluconeogenensis pathway promoting the TCA Cycle intermediates or Oxaloacetate to convert into Phosphoenolpyruvate and promoting gluconeogenesis to balance the blood glucose level.
These are the same effects produced by glucagon to increase the blood glucose level when it is low.
My question then is what is the need for release of Cortisol? Also, if its release is important to control other pathways I haven't mentioned here, then why does cortisol produce the same effects as glucagon? Why is glucagon alone not enough to maintain blood glucose level?