How is acromegaly diagnosed?

The delay in diagnosis is about 10 years because physical changes linked to acromegaly develop slowly and insidiously. The varied symptoms of acromegaly can make diagnosis challenging. Many of the initial signs of the disease can be attributed to other conditions. This is why the delay in diagnosis can be long. Patients often first seek medical advice for orthopedic or rheumatologic symptoms, cardiac events, or even dental disorders. Often, acromegaly is suspected when a patient sees a new physician for the first time and he/she is struck by the patient’s current characteristic facial appearance. Comparing old photographs from a number of different time periods will often increase suspicion of the disease. 

When acromegaly is suspected, you have to be referred to an endocrinologist (a specialist in hormone related conditions). A detailed physical examination will be done to look for signs and symptoms. To make the diagnosis, important screening tests will be ordered. They will include blood work, an oral glucose tolerance test (OGTT) to confirm GH hypersecretion, pituitary magnetic resonance imaging (MRI) to visualize the tumour, and visual field examination to identify pressure on the optic nerves. 

These tests are explained in this module. 

Blood Work for the GH overproduction 

GH and IGF-1

Blood will be drawn and tested for random plasma levels of GH and IGF-1. 

Oral Glucose Tolerance Test (OGTT)

OGTT is the most important test to diagnose acromegaly. You must fast overnight. In the morning, you will be given an orange sugar solution to drink. Your plasma GH levels will then be measured every half hour for 2-3 hours. The sugar solution should decrease plasma GH levels if you do not have acromegaly. Plasma IGF-1 levels above the normal sex and age-adjusted range and plasma GH levels greater than a determined cut-off under OGTT confirm the diagnosis of acromegaly. 


Pituitary MRI

MRI gives a three-dimensional detailed computer image of the pituitary. This is needed by the surgeon in order to see the size and location of the tumour and if there is invasion of the surrounding structures. This test can take up to 60 minutes and no preparation is needed. In cases of MRI contraindications, such as a pacemaker or metallic implants, the MRI could be replaced by a pituitary computed tomography or CT scan, however, both of these are less precise than an MRI to see pituitary tumours.  

A pituitary MRI should be done when screening, sometimes during the surgery, post-operatively and yearly for ongoing monitoring.

Visual Fields 

The visual field test is performed to see whether the tumour has compressed the optic nerves that are located close to the pituitary gland. This test takes approximately 30-45 minutes and no preparation is needed. 

This should be done when screening, post-operatively and on the recommendations of your endocrinologist. If at any time you are noticing visual changes, please inform your endocrinologist, as visual field testing may need to be performed as soon as possible. This could be an indication that some residual tumour may have grown. 

Additional tests 

When the diagnosis is confirmed, the following tests are also important to determine complications of acromegaly. 

Metabolic and hormonal blood work

Blood work to test glucose, electrolytes, lipids, and other hormones such as TSH, T4, prolactin or PRL, cortisol, LH, FSH, and testosterone.

You must fast overnight and should have your blood drawn the next morning between 8-9 am at your nearest lab. 

Electrocardiogram and Echocardiogram

These procedures evaluate heart function. An echocardiogram can take approximately 60-90 minutes.

No preparation for this test is needed. 

Ultrasound of the gall bladder

This procedure is used to determine if gallstones or polyps (harmless tumours) are present in the gallbladder before the medical treatment of acromegaly. It can take approximately 1 hour.

There is preparation required for this test.* 


Colonoscopy is necessary to evaluate if polyps (benign tumours) have developed in the large intestine. If so, they should be removed during the same exam because they may eventually become cancerous. This test can take approximately 1-2 hours.

There is preparation required for this test.* 

Polysomnography (sleep study)

A polysomnography is used to check if you have sleep apnea. A polysomnography is often ordered for patients with complaints of daytime fatigue or sleepiness that may be caused by interrupted sleep. It is usually performed at night, at the hospital or at home.


Bone Mineral Density (BMD)

Bone mineral densitometry is an enhanced x-ray that measures bone loss. A BMD test can tell whether or not you have osteoporosis and how likely you are to develop it in the future. Osteoporosis puts you at risk for fractures. This test can take approximately 20-30 minutes.

No preparation for this test is needed.

*When preparation is required for a test, information will be given to you when you are given the date and time of the appointment.


Baseline Tests






Visual Field:












Gallbladder Ultrasound:



Bone Density:



Test Dose:













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