What are GH (or hGH) and IGF-1?

I am not a doctor. What I write here is what I know, it could be wrong. If you’re a doctor and you see any mistakes here, please, contact me.

GH : Growth Hormone (also called hGH, human growth hormone)

IGF-1: Insuline-like Growth Factor 1

GH is the hormone you used as a child to grow up. Its value differ depending on the age of the person, being higher for babies, children and teenagers and low in adults. The excessive production of GH in adults, after the growing phase is over, leads to enlargening of hands, nose, feet, tongue, can widen your jaw… well, it leads to the common symptoms of acromegaly. Excessive production of GH in children leads to a condition called gigantism.

So, in order to diagnose with acromegaly, measuring GH is necessary. However, a single blood sample of GH does not show much. It peaks for a variety of reasons throughout the day and a single test at a given moment can show a very high value of GH that does not correspond to the normal (basal) value. So, don’t get scared if it’s your first blood test and GH is over the limits. Peaks (in healthy people) can even reach 45 ng/ml! The peaks can occur after (or while) exercising, one hour after falling asleep, depend on your stress level, nutrition level… The proper test to assess the value of GH and to give the acromegaly diagnosis is the OGTT. Not only they want to see how your body supresses GH, but they need to be sure they are not measuring GH during a peak.

Ok, now you know GH is not very stable and a single measurement is not enough. But there are other blood tests, normal ones, where a single blood sample can offer a lot of information about gour GH levels. There is another hormone, IGF-1, insuline-like growth factor 1, it is produced in the liver and the production is ruled by GH. The more GH you produce, the more IGF-1 your liver will make. It is pretty straightforward: basically a single measurement showing a high level of IGF-1 means you are always producing too mugh GH. A normal level of IGF-1 means you have the normal GH value most of the time (at least this it the common knowledge, reality is far more complicated: there have been people diagnosed with acromegaly with normal IGF-1 and high GH plus other symptoms -enlarged hands, tongue, ears, nose…- , there are people with low IGF-1 and high GH for no reason, etc.).


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