Cortisol is a hormone produced by the adrenal glands. Production of cortisol is stimulated by ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland.
Cortisol has a lot of functions in the body. It helps break down protein, glucose, and lipids, maintain blood pressure, and regulate immune system.
The hormone is secreted mainly during the early morning and less during the evening.
Variations of cortisol can cause symptoms such as weight loss, muscle weakness, fatigue, low blood pressure, and abdominal pain.
High cortisol levels cause increased blood pressure, high blood sugar, obesity, fragile skin, purple streaks on the abdomen, muscle weakness, and osteoporosis. Women can have irregular menstrual periods and increased facial hair. Children may have delayed development and a short stature.
Blood and urine tests for cortisol help diagnose Cushing's syndrome and Addison's disease.
Typically, blood will be drawn from a vein in the arm, but sometimes urine or saliva may be tested.
Purpose of the test
The purpose of the test is to help diagnose Cushing's syndrome or Addison's disease. It is prescribed when doctor suspects excess or deficient cortisol production.
Cortisol test may be prescribed when a patient has symptoms that suggest Cushing’s syndrome (obesity, muscle wasting, and muscle weakness) or Addison’s disease (weakness, fatigue, increased pigmentation, among others).
Suppression or stimulation testing is ordered after an initial test result is abnormal. Cortisol testing may be also ordered repeatedly when patients are being treated for Cushing’s syndrome or Addison’s disease to check the effectiveness of treatment.
Reference range values
Cortisol levels are normally very low at bedtime and very high just after waking. This pattern will change if a person works irregular shifts and sleeps at different times of the day. With Cushing’s syndrome, this pattern is typically lost.
Increased or normal cortisol concentrations in the morning plus levels that do not drop in the afternoon and evening suggest an overproduction of cortisol. This can be cause by increased pituitary, tumor outside of the pituitary, problem with the adrenal gland, or medication.
Pregnancy, physical and emotional stress, hyperthyroidism and obesity can increase cortisol levels. A number of drugs can also increase levels, particularly oral contraceptives, hydrocortisone, and spironolactone.
Adults have slightly higher cortisol levels than children.
Hypothyroidism may decrease cortisol levels. Drugs that may decrease levels