Understanding your test results
The results of any tests you may have are individual to you and you should always talk to your doctor or other healthcare team member if there is anything that you do not understand or that you would like to be explained further.
Below is a general guide to interpreting the results of some of the blood tests and other assessments that may be used, either to diagnose or to help monitor your condition in the long term.
Growth hormone and IGF-1
Growth hormone and insulin-like growth factor 1 (IGF-1) are measured in micrograms per litre of blood (g/L). IGF-1 may also be measured as nanomoles per litre (nmol/L), which is a different way of expressing its concentration.
What is the difference between acromegaly and gigantism?
It is hard to define, what a “normal” level of growth hormone is, because the hormone is secreted in bursts and does not stay in the blood stream for long. This is why a random growth hormone level cannot be used as the only laboratory value to find out whether a person has acromegaly or not.
An oral glucose tolerance test (OGTT) will give a better indication of whether a person has an overproduction of growth hormone that is characteristic of active acromegaly.
This is because the normal secretion of growth hormone by the pituitary is suppressed by the presence of large amounts of glucose in the bloodstream.
There are different cut-offs to which growth hormone should be suppressed during the test. The critical cut-off is a growth hormone level higher than 1 μg/L. Ask your healthcare professional to explain the test result to you.
What are normal levels of IGF-1?
IGF-1 levels depend on a person’s age and sex, but also on the test kit (called an assay) the laboratory uses.
Adolescents have the highest levels of IGF-1, peaking around the age of 13 to 15 years. IGF-1 levels then decline and become lower with increasing age.
Usually, the lab will provide the normal range for its test, according to the sex and age of a person, together with the actual IGF-1 test result.
What is biochemical control?
One of the goals of acromegaly treatment is to achieve biochemical control or biochemical normalization.
This is where levels of both growth hormone and IGF-1 are reduced to be within the normal range.
Blood sugar (glucose)
The amount of glucose in your blood may be routinely monitored if you have, or are at risk of developing, diabetes mellitus. This is a common coexisting condition that people with acromegaly may have.
There are three ways of measuring your blood glucose:
Fasting glucose test
This is a test in which the level of glucose in your blood is measured after you have not eaten or drunk anything other than water for several hours or overnight.
Results are usually expressed as millimoles per litre (mmol/L).
- A value below 5.6 mmol/L is considered normal
- Values between 5.6 and 6.9 mmol/L are borderline and indicate impaired fasting glucose in the body
- Values of 7.0 mmol/L or above on two separate tests are indicative of diabetes mellitus
This is the same test that is used for measuring growth hormone suppression. It will also give information on whether your body is capable of clearing glucose away from blood quickly. Your blood glucose levels are again checked after not eating for a few hours, then rechecked 2 hours after you have had the glucose drink.
- A blood glucose of less than 7.8 mmol/L at 2 hours indicates normal glucose metabolism or tolerance
- A value between 7.8 and 11.0 mmol/L shows there is impaired glucose tolerance
- A value of 11.1 mmol/L or higher suggests that the individual probably has diabetes mellitus
HbA1c, or glycosylated hemoglobin, is a subtype of the red blood pigment hemoglobin that is formed by hemoglobin’s exposure to plasma glucose, a process called glycosylation.
This test gives information on the average plasma glucose concentration over the past 2–3 months, which is the average life span of red blood cells.
A value of 6.5% or higher on two separate tests suggests that you have diabetes.
HbA1c is also measured in people who already have diabetes mellitus to give an accurate picture of their blood glucose control.
Blood pressure results are given as millimetres of mercury, or mmHg. There are two numbers usually written one on top of the other or with one given before the other.
In the image example, the top or first number (<120 mmHg) gives a measure of the highest pressure when blood is pumped from the heart out into the bloodstream. This is called the systolic blood pressure.
In the image example, the bottom or second number (<80 mmHg) gives a measure of the pressure in the arteries when the heart is resting between beats. This is called the diastolic blood pressure.
For most young people without any form of illness, the systolic blood pressure should be less than 120 mmHg and the diastolic blood pressure should be less than 80 mmHg.
Hypertension, which is a common comorbidity associated with acromegaly, occurs when these blood pressure values rise to be 140 mmHg or higher and 90 mmHg or higher, respectively.
Body mass index
Your doctor may use your height and weight to calculate your body mass index, or BMI.
This is an approximate measure of whether someone is underweight, of normal weight or overweight.
However, because of the type of body changes that can occur in people with acromegaly, the BMI may be a less reliable indicator of their body weight.
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Find out how acromegaly is diagnosed and the tests that healthcare professionals may use to monitor acromegaly symptoms caused by excess growth hormone in the body due to a pituitary tumour.
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Read answers to some common questions that patients with acromegaly have asked