Insight into your IGF-1 level.
IGF-1 is produced in the liver under the influence of growth hormone. The level gives insight into growth hormone production over a longer period, whereas growth hormone itself fluctuates sharply throughout the day.
Also known as: IGF1, Somatomedin C, Insulin-like growth factor 1
Personal assessment by our BIG-registered doctors
By the Bloodworks editorial team
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Background
What is IGF-1?
IGF-1 stands for insulin-like growth factor 1, formerly known as somatomedin C. It is made mainly in the liver, under the influence of growth hormone released by the pituitary gland. In the blood, IGF-1 circulates bound to binding proteins, which keeps the level steady throughout the day. IGF-1 plays a role in tissue growth and in the metabolism of cells.
Growth hormone itself is released in short bursts, mostly at night, and is barely measurable in between. A single growth hormone measurement therefore says little. IGF-1 changes far more slowly and reflects production over a longer period, which makes it the more practical test in daily practice. The level does depend strongly on age and on nutritional status, and a liver condition or poorly controlled diabetes can affect the result as well. An abnormal value is therefore not a diagnosis in itself.
In brief
Liver
Made there under the influence of growth hormone from the pituitary
Steady during the day
Growth hormone comes in bursts, IGF-1 changes far more slowly
Age-dependent
The level changes with age, and the laboratory takes that into account
Nutritional status
Prolonged fasting and undernutrition lower the level
Common reasons to test
When can insight into your IGF-1 be valuable?
Below are some situations in which measuring IGF-1 can provide insight.
Insight into your IGF-1 level
A test shows where your IGF-1 currently stands.
As an alternative to a single growth hormone test
Growth hormone is released in short bursts and is barely measurable in between. IGF-1 is steady during the day and is therefore more practical to measure.
If you have questions about the pituitary
The pituitary gland drives the production of growth hormone. IGF-1 gives an impression of that drive over a longer period.
As part of a broader hormone check
IGF-1 can be combined with other hormone tests in the same blood draw, for example testosterone, cortisol or insulin.
With a strongly restricted nutritional status
Prolonged fasting, a strict diet or reduced absorption of nutrients lowers IGF-1. That context belongs with the assessment of the result.
With a known liver condition
IGF-1 is produced in the liver. With a known liver condition the level can come out lower, separately from growth hormone production itself.
To follow up an earlier measurement
If your IGF-1 has been measured before, a repeat test shows how the level develops over time.
What your result means
How do we read your IGF-1 level?
IGF-1 is measured in nanomoles per litre (nmol/L) or in micrograms per litre (µg/L). The laboratory states the reference values that apply there alongside your result, and those are leading. For IGF-1 those values depend on age, and nutritional status counts as well. The result is therefore always read in context rather than as a single number.
A low value
A low IGF-1 fits with a reduced nutritional status, for example prolonged fasting, a strict diet or reduced absorption of nutrients. A liver condition, poorly controlled diabetes or a thyroid condition can also push the level down. IGF-1 additionally declines gradually with age. A low value is not a diagnosis in itself. Our doctor looks at the whole picture rather than this number alone.
A normal value
An IGF-1 within the laboratory's reference values is a reassuring result for this marker. Bear in mind that IGF-1 reflects growth hormone production over a longer period and moves with age and nutritional status. A single measurement is not a diagnosis.
An elevated value
An elevated IGF-1 needs to be explained in context. The level is tied to age and to the stage of growth, and is naturally higher in adolescents during puberty than in adulthood. A single elevated result therefore says little on its own. Our doctor will discuss what the result means in your situation and whether follow-up through your GP is worthwhile.
How we interpret your result
Related tests
Often combined with IGF-1.
A single marker gives one perspective. For a broader picture you can combine IGF-1 with a theme package or related markers.
+ €29 blood draw fee per orderFree from €225
Frequently asked questions
Everything you want to know
Do I need to fast for an IGF-1 test?
Fasting is not necessary for IGF-1. It is wise, however, not to have your blood drawn straight after a long fast or a strict diet, because that temporarily lowers the level. If you combine the test with glucose or cholesterol, for example, the fasting instructions do apply to those tests.
Why do you measure IGF-1 rather than growth hormone itself?
Growth hormone is released in short bursts, mainly at night, and is barely measurable in between. A single measurement can therefore come out high or low without meaning much. IGF-1 is produced in the liver under the influence of growth hormone and changes far more slowly, which gives a picture over a longer period.
Is somatomedin C the same as IGF-1?
Yes. Somatomedin C is the older name for the same substance. You will come across both terms on request forms and in results. We measure and report the value as IGF-1.
Why does my age matter for this result?
IGF-1 is naturally highest around puberty and declines gradually with age after that. A number can therefore only be placed alongside your age. The laboratory states the reference values that apply there alongside your result, and those are leading.
Does my diet affect the result?
Yes. Nutritional status has a clear influence on IGF-1. Prolonged fasting, a strongly reduced intake or reduced absorption of nutrients lowers the level. Do mention it during your intake if this applies to you, so the doctor can take it into account.
Does the time of day of the blood draw matter?
No, not in the way it does for growth hormone or cortisol. IGF-1 is steady during the day, so the timing of the draw is not decisive. In practice most people have blood drawn in the morning, which is convenient if you combine the test with ones where timing does matter.
Can I combine IGF-1 with other tests?
Yes, every test you choose is done in a single blood draw. IGF-1 is often requested alongside other hormone values, for example testosterone, cortisol, insulin or SHBG. You then pay the blood draw fee only once.
What happens if my level is abnormal?
You receive your result with a personal explanation from our doctor, who explains what the value means in your situation and whether further testing is worthwhile. An abnormal IGF-1 is not a diagnosis. If you have symptoms, your GP remains the right starting point, because an assessment involves more than blood alone.
Ready for insight into your IGF-1 level?
You receive your IGF-1 level including a personal explanation from a doctor, usually within 2 working days. No referral needed.
Order IGF-1 →Want to test multiple markers at once?
Combine IGF-1 with other markers via Bloodworks Select. The blood draw and collection fee is charged once per order, and is waived from €225.
80,-
+ €29 blood draw fee+ €29 blood draw fee per order