Differential Diagnosis for Cushings Syndrome

Cushing's Syndrome is an endocrine disorder caused by long-term exposure to cortisol. Cortisol is a hormone which is produced in your body and contained in many oral corticosteroids. Cushing's syndrome can be caused by long-term medication use or your body's overproduction of cortisol. The condition is fairly rare but most prevalently affects adults between the ages of 20 to 50.

Symptoms

• Some of the characteristic Cushing's syndrome symptoms include pink/purple stretch marks, rounded face and a hump of fatty tissue between your shoulders. Additional symptoms include obesity (predominately in the upper body), increased neck fat, increased bruising, hypertension, high blood sugar levels, increased urination, abnormal thirst, flushing of the face, decreased sex drive, headaches, bone loss and acne.

  Women may additionally experience menstrual irregularities and excessive hair growth on the neck, back, chest and face. Men may additionally experience erectile dysfunction and decreased fertility. Children with the condition often grow slowly and are obese.

Other Possible Conditions

• There are other conditions which can mimic those of Cushing's syndrome. For example: polycystic ovary syndrome can account for weight gain, menstrual irregularity, excessive hair growth and abnormal insulin response/diabetes.
  Metabolic syndrome can also cause weight gain, carrying excess fat in the waist area, hypertension, high cholesterol levels and insulin resistance. Alcohol abuse and depression can also mimic some of the symptoms of Cushing's syndrome. This makes diagnosing Cushing's syndrome challenging. Your doctor will need to review your full history, examine you and run some laboratory tests.

Diagnosis

• According to researchers at St Bartholomew's and The Royal London School of Medicine and Dentistry in London, one of the most reliable diagnostic tests is the low-dose dexamethasone suppression test which delivers low doses of dexamethasone (which is a man-made glucocorticoid. For two days, you are given a dose every 6 hours. Your urine is collected both before the drug is given and several times throughout the day of the test. This measures your cortisol levels at specific times. If at midnight, you have a cortisol level greater than 50 nanomoles per liter indicates Cushing's syndrome while having levels lower than this will rule Cushing's syndrome out.

Additional Diagnostic Tests

• Additional tests may be necessary in some cases to make a differential diagnosis. They may include one of the following:
  24-hour urinary free cortisol tests measure cortisol levels in urine that you collect over the course of 24-hours. Cushing's syndrome is indicated if your levels are greater than 50 to 100 micrograms per day.
  Late-night salivary cortisol measurements take a saliva sample to study the cortisol levels.
  Midnight plasma cortisol tests evaluate your blood's concentration of cortisol. Since your body generally does not produce cortisol at night, the presence of cortisol in levels higher than 50 nanomoles per liter indicates possible Cushing's syndrome.
  CRH (dexamethasone-corticotropin-releasing hormone) tests can differentiate pseudo-Cushing's syndrome by measuring any raise in cortisol levels.

Considerations

• Catching the condition as early as possible enhances your chances for making a full recovery. Treating the cause of the condition can return your body's production of cortisol to normal levels and help to improve your symptoms. If you are at risk of developing the condition, you should talk to your doctor about your risk factors and possibly be tested.