Why dos someone develop hypokalemia if they have cushings disease?

Cushings: Cushing's disease involves excess cortisol, which is a glucocorticoid, which makes you round, thin skin, diabetes, etc. However, cortisol has a little mineralocorticoid effect (like aldosterone). Normally this is not significant, but when cortisol levels are high, the aldosterone-like effect will make you hypokalemic.

Cushing's Disease: Cushing's is caused by too much cortisol/cortisone. This may activate the receptors that aldosterone uses to cause to pee out potassium when you eat too much salt. The low K can likely be helped by moving to the DASH diet. Discuss with your Dr.