How Do You Test for Acromegaly?

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Note from a doctor who diagnoses acromegaly

Acromegaly is a severe disease that involves a hypersecretion of the growth hormone (GH) after the closure of the epiphyseal growth plates which occurs in adults between ages 20 to 50. The abnormal growth is caused by the excessive action of insulin growth factor 1 (IGF-1) that occurs after the epiphyses fuse in adulthood. Acromegaly is almost always caused by a benign pituitary tumor. Morbidity and mortality rates are high in acromegaly due to the associated symptoms such as respiratory, cardiovascular, and cerebrovascular malignancies and disorders.

To begin the diagnostic process of acromegaly, the doctor asks for the patient’s medical history and conducts a physical exam. These are the following procedures that are performed to diagnose acromegaly:

Physical Exam

The physical exam is done by the doctor if he/she suspects acromegaly in a patient to determine if the patient has symptoms of the disease such as coarsening of the facial features, enlargement, and swelling of the hands and feet, protrusion of the jaws, etc. The doctor may ask to see older photographs of you that have been taken over many years to be able to compare facial features. High blood sugar levels and high blood pressure are also signs of acromegaly.

Blood Test

Blood tests confirm the diagnosis of acromegaly when they show high levels of the growth hormone and insulin-like growth factor 1 (IGF-1). There are 2 key blood tests to determine if a patient is suspected to have acromegaly:

Insulin-like Growth Factor-1 or IGF-1 Test – The patient is required to fast overnight to test the growth hormone levels. The doctor takes a blood sample to measure the levels of GH and IGF-1. Elevated levels of these hormones indicate acromegaly.

IGF-1 is a hormone that is closely associated with the growth hormone. When the pituitary gland secretes growth hormone it prompts the release and production of IGF-1 from the liver and some other tissues which causes the tissues in the body to grow. IGF-1 levels are high when the growth hormone levels are high. IGF-1 levels are much more stable compared to GH levels because of the dramatic fluctuation of GH levels that’s why this is a more reliable test. The IGF-1 test can be done with just a single shot at any time of the day even without fasting. A high IGF-1 level for an individual who does not have acromegaly is the body’s indication to stop generating GH. For an individual with acromegaly, the body continues to generate GH even if the IGF-1 levels are high.

Oral Glucose Tolerance Test (OGTT) – Blood glucose levels are associated with growth hormone levels. For someone who doesn’t have acromegaly, having a higher blood glucose level normally causes the body to stop producing growth hormone. A single high level of GH in the blood is not enough to make the diagnosis of acromegaly because GH is usually released in short bursts and the levels of GH often fluctuate dramatically. OGTT is the definitive method for diagnosing acromegaly. This is administered by the doctor by giving the patient a glucose drink to suppress growth hormone levels and watching how the GH level responds after taking the drink. The blood levels in the GH are measured before and after drinking the glucose drink. If the GH level does not drop to below 1ng/mL during the OGTT, it means that the patient has acromegaly. OGTT is not required if the clinical features of acromegaly are too obvious, an adenoma is detected in the pituitary gland through MRI or CT scan, or the IGF-1 level is high.

Pituitary Function

The confirmation of acromegaly through the blood tests can prompt the doctor to check if the other parts of the pituitary gland that are not affected by the tumor are still functioning properly. This is done by testing the blood to check the other pituitary hormones.

Imaging Tests

Imaging Tests such as computerized tomography (CT scan) or Magnetic Resonance Imaging (MRI) is done to look for abnormal growths or tumors in the pituitary gland. These scans are usually recommended by the doctor to help pinpoint the size and location of a tumor in the pituitary gland. Radiologists are the ones who perform the procedure. If they don’t find any tumor or adenoma in the pituitary gland, they can look for nonpituitary tumors that may be responsible for the increased levels of GH. They use MRI to detect adenomas or tumors in the pituitary gland and they use CT scan to detect ovarian, pancreatic, abdominal, and adrenal tumors secreting growth hormones.

Radiography

Radiography is done to demonstrate skeletal manifestations of the excess GH or IGF-1. Imaging of the skull may show enlargement of the nasal sinuses and thickening of the bones. Hand x-rays show the swelling of the tissue around the bones and the thickening of the bones under the fingertips.

To diagnose acromegaly, it involves a combination of the different procedures: taking note of the physical changes in the body, testing the levels of GH and IGF-1 in the blood, and confirming the presence, size, and location of tumors using imaging tests.