Growth hormone and insulin-like growth factor 1 (IGF-1) are measured in micrograms per litre of blood (μg/L). IGF-1 may also be measured as nanomoles per litre (nmol/L), which is a different way of expressing its concentration.
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 better information 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 health care professional to explain the test result to you.
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 laboratory 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.
One of the goals of acromegaly treatment is to achieve biochemical control or biochemical normalisation.
This is where levels of both growth hormone and IGF-1 are reduced to be within the normal range.
The aim is to get levels of growth hormone to be less than 1.0 μg/L but may vary depending on international guidelines and local practices.
IGF-1 should be reduced to a level that would be normal for the age and sex of the person.
The amount of glucose in your blood may be routinely monitored if you have, or are at risk for developing, diabetes mellitus. This is a common coexisting condition that people with acromegaly may have.
There are three ways of measuring your blood glucose:
This is where 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 given as millimoles per litre (mmol/L).
This is the same test that is used for measuring growth hormone suppression. It will also give information of 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.
HbA1c, or glycosylated haemoglobin, is a subtype of the red blood pigment haemoglobin that is formed by haemoglobin’s exposure to plasma glucose, a process called glycosylation.
This test gives information on the average plasma glucose concentration over the past 6–8 weeks, which is the average life span of red blood cells.
HbA1c is usually measured in people who already have diabetes mellitus to give an accurate picture of their blood glucose control.
Results may be written as a percentage or as a number in millimoles per mole (mmol/mol). A value of 6.5% or less or less than 48 mmol/mol in someone with diabetes is considered the goal according to European guidelines.
Blood pressure results are given as millimeters of mercury, or mmHg. There are two numbers usually written one on top of the other or with one given before the other.
The top or first (<120 in the example given) number 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.
The bottom or second number (<80 mmHg in the example given) 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.
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.
Learn about acromegaly including what causes this slowly evolving condition, and the early signs and symptomsLearn about acromegaly
Read about acromegaly treatment options, including surgery, medications and radiotherapy, and the goals of therapyTreating acromegaly
Read and hear answers to some common questions that patients with acromegaly have askedView FAQs