is a hormone produced by the adrenal gland (which is located above the kidney
Abnormally high levels may indicate an adrenal tumor
A one time blood test
is usually insufficient to diagnose a problem with cortisol. The doctors may order a 24 hour urine free cortisol test which measures the level of cortisol in the urine over a 24 hr period. Since cortisol levels fluctuate during the day, this test is more accurate.
Increased cortisol levels is also associated with Cushings Syndrome which may explain your obesity.
Hope this helps. Ask your doctor for additional information and what the next step in management is for you.