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Corticosteroid-Binding Globulin (CBG) Blood Test

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The Corticosteroid-Binding Globulin (CBG) Blood Test measures CBG levels in the blood to diagnose and monitor cortisol-related conditions like Cushing's syndrome and Addison's disease.


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Test Code:


CPT Code(s):


Also Known As:

CBG, Corticosteroid-binding Globulin (CBG) Transcortin


Radioimmunoassay (RIA)




No special preparation required.

Test Results:

7-10 days. May take longer based on weather, holiday, or lab delays.

Walk-In Lab is prohibited from selling LabCorp tests to residents in the following states:NY, NJ, RI, MA, MD

What is CBG?

Corticosteroid-binding globulin (CBG) is an essential protein found in the blood that plays a vital role in transporting cortisol, a hormone that regulates several bodily functions such as metabolism, immune response, stress response, blood pressure, and heart function. CBG binds with cortisol and other steroid hormones, such as progesterone and testosterone, and helps regulate their movement through the bloodstream, ensuring that they reach the cells and tissues where they are needed.


What is the purpose of this test?

The Corticosteroid-Binding Globulin (CBG) blood test is a medical test that measures the level of CBG protein in the blood. Healthcare providers usually recommend this test to help diagnose and monitor conditions related to cortisol levels, such as Cushing's syndrome and Addison's disease. 

Cushing's syndrome is a hormonal disorder that results from prolonged exposure to high levels of cortisol in the blood. This condition can cause a variety of symptoms, such as weight gain, high blood pressure, mood changes, increased risk of infections, and upper-body obesity with thin arms and legs. On the other hand, Addison's disease is a condition in which the adrenal glands do not produce enough cortisol and other steroid hormones. Symptoms of Addison's disease include fatigue, weight loss, low blood pressure, and darkening of the skin. The CBG blood test may also be used to monitor the effectiveness of treatment for these conditions or to evaluate the function of the adrenal glands. 

Apart from Cushing's syndrome and Addison's disease, the CBG blood test can also diagnose other conditions that affect cortisol levels, such as liver disease, kidney disease, and thyroid disorders. The test also helps healthcare providers to evaluate the effectiveness of treatment for these conditions. In conclusion, the CBG blood test is an important tool that helps healthcare providers diagnose and monitor various hormonal disorders, evaluate the effectiveness of treatment for these conditions, and provide timely and appropriate medical intervention to manage the symptoms and prevent complications.


When should I order a Corticosteroid-Binding Globulin (CBG) Blood Test?

Individuals may order this test if they have experienced symptoms of a cortisol-related disorder such as Cushing's syndrome or Addison's disease. Common signs or symptoms of a cortisol-related disorder include:

Symptoms of Cushing's syndrome include:

  • Weight gain, particularly around the midsection and upper back
  • Rounded face
  • Excess hair growth on the face, neck, chest, and back in women
  • Thin skin that bruises easily
  • Slow healing of cuts and wounds
  • Acne
  • Muscle weakness
  • High blood pressure
  • High blood sugar
  • Mood swings
  • Depression and anxiety
  • Irregular menstrual periods in women

Symptoms of Addison's disease include:

  • Extreme fatigue
  • Weight loss and decreased appetite
  • Darkening of the skin (hyperpigmentation)
  • Low blood pressure
  • Salt craving
  • Nausea, vomiting, and diarrhea
  • Muscle or joint pain
  • Irritability and depression
  • Body hair loss or sexual dysfunction in women
  • Menstrual changes in women
  • Low blood sugar (hypoglycemia)

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