Cushing's syndrome occurs when there is too much cortisol

A tumour in the pituitary gland (highlighted in yellow) that causes too much cortisol to be produced is known as Cushing’s disease (which is not the same as Cushing’s syndrome). — Filepic

Cushing’s syndrome is a disorder that happens when your body produces too much of a hormone called cortisol.

It can also be called hypercortisolism.