What an IGF-1 result actually tells you

An IGF-1 result is a monitoring number. It is not a dial you turn. If you are using growth hormone that no clinician prescribed for you, and you are weighing whether to push the dose higher or swap to tesamorelin, that is not a question a website should answer for you. What we can do is set out what the number represents, what tesamorelin is actually licensed to treat, and what the trial evidence says about growth hormone in people who are not deficient.

What IGF-1 actually measures

IGF-1 (insulin-like growth factor 1) is produced mainly by the liver in response to growth hormone. Circulating growth hormone arrives in pulses, so a single blood draw can catch a peak or a trough and tell you very little. IGF-1 is the steadier downstream proxy, which is why it shows up in monitoring instructions rather than as a target to hit.

Look at how the one licensed drug in this space treats it. The US prescribing information for tesamorelin tells prescribers to monitor IGF-1 during treatment and to consider discontinuing the drug in patients with persistent elevations^[1]. That is written as a stop signal. It is not a step-up rule, and nothing on the label frames a higher IGF-1 reading as a goal.

Why one value cannot answer a dosing question

The Endocrine Society clinical practice guideline on adult growth hormone deficiency states that confirming the diagnosis usually requires stimulation testing, unless there is a proven genetic or structural lesion^[2]. A lone IGF-1 figure therefore cannot establish whether the growth hormone axis was underperforming in the first place. Without a value drawn before anything was injected, it also cannot show what changed.

So the reasoning behind "raise it until the number moves" runs backwards. On the only product in this class holding a marketing authorisation, a rising IGF-1 reading is the thing that prompts a prescriber to consider stopping. Chasing the value upward inverts the safety logic the label was written around.

What tesamorelin is licensed for

Tesamorelin is a synthetic analogue of growth-hormone-releasing hormone. It acts on the pituitary so the body releases its own growth hormone in pulses, rather than receiving a fixed dose from outside, which is the design difference from injected growth hormone. In the United States it is sold as Egrifta, and the labelled indication is narrow: "reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy"^[1]. The same label carries an explicit limitation of use, that it "is not indicated for weight loss management", and contraindicates it in active malignancy, in disruption of the hypothalamic-pituitary axis, and in pregnancy. Prescribers are told to check glucose status before starting and to monitor patients periodically afterwards. More background sits on our tesamorelin page.

The evidence behind that indication is specific. A randomised, double-blind trial published in JAMA in 2014 enrolled 50 antiretroviral-treated adults with HIV and abdominal fat accumulation, who received tesamorelin 2 mg or placebo daily for six months. Visceral adipose tissue fell by 34 cm2 on tesamorelin against a rise of 8 cm2 on placebo, and liver fat fell 2.0% against a 0.9% rise^[3]. That is a real effect in a defined patient group with a defined problem. It is not evidence about body composition in someone who does not have that problem.

In Europe there is no authorised tesamorelin product at all. The EU marketing-authorisation application was withdrawn in June 2012 after the CHMP said the data did not allow it to conclude on a positive benefit-risk balance. Among the concerns the committee listed: elevated IGF-1 levels in many patients, which it tied to cancer risk and diabetic eye disease, and the absence of long-term safety data^[4]. A European regulator wrote down, in 2012, the precise worry that a high IGF-1 reading is meant to flag. The jurisdiction-by-jurisdiction picture is on our regulation pages for the United States, the United Kingdom, Denmark and Germany.

Growth hormone in people who are not deficient

The most useful synthesis here is a systematic review published in Annals of Internal Medicine in 2008, pooling 27 study samples covering 303 participants who received growth hormone. Those participants were young (mean age 27), lean (mean BMI 24) and fit. Lean body mass rose by 2.1 kg relative to controls, but "strength and exercise capacity did not seem to improve", and soft tissue oedema and fatigue occurred more often than in untreated controls. The authors concluded that "claims that growth hormone enhances physical performance are not supported by the scientific literature"^[5].

The lean body mass figure travels well on its own. The rest of that finding, that strength did not follow it and that swelling and fatigue did, tends not to. Fluid retention adds mass without adding function, and a review that reports both is telling you which one the participants got.

Where this leaves the question

Growth hormone bought outside a prescription sits outside every approved indication for it, which also means nobody is doing the monitoring the labels ask for. The same applies to the growth hormone secretagogues that circulate alongside it, such as ipamorelin and CJC-1295, neither of which is an approved medicine anywhere in our coverage area. Glucose checks, IGF-1 tracking and a contraindication screen are part of how a licensed product is used safely, and none of them happen with a vial from a source.

If you are holding an IGF-1 result you cannot read, the useful next step is an endocrinologist who can order the baseline you skipped and the stimulation testing that actually establishes deficiency. We are not going to tell you whether to raise a dose or switch a drug. That decision needs a prescriber who has your history, your labs, and legal responsibility for what happens next.