Peptide Health Lab

Growth hormone axis

HGH (somatropin)

Also known as: Somatropin, Recombinant human growth hormone, rhGH

Regulatory status
FDA approved
Evidence grade
Human RCT evidence

Last reviewed September 1, 2026 · 12 sources

What HGH is and how it works

Human growth hormone is a 191-amino-acid protein made by the anterior pituitary and released in pulses, mostly at night, under the opposing control of growth-hormone-releasing hormone and somatostatin. Somatropin is recombinant human growth hormone: the same sequence, manufactured in cell culture rather than extracted from a person. Almost every other compound in the growth-hormone section of this library — sermorelin, tesamorelin, CJC-1295, ipamorelin — is a secretagogue that asks the pituitary to release more of this. Somatropin is the hormone itself, which is why it works regardless of whether a pituitary is functioning and the secretagogues do not.[8]

Growth hormone acts partly through its own receptor and largely through IGF-1, which the liver produces in response and which mediates most of the anabolic signal: whole-body protein synthesis including skeletal muscle and collagen proteins. It is also lipolytic and it opposes insulin action, which is where both the fat-loss reputation and the glucose problem come from.[7] The hormone circulates as a family of isoforms in a pulsatile pattern with rapid clearance — a detail that turns out to matter enormously for detecting exogenous administration, since injected recombinant hormone is a single 22-kDa species.

The history is unusual and worth knowing, because it is the reason the modern product exists. Before recombinant manufacture, therapeutic growth hormone was derived from human cadaver pituitary glands, collected at autopsy and pooled by the thousands. National programmes distributed it to children with growth failure from the late 1950s until 1985. That material carried Creutzfeldt-Jakob disease prions. In a United Kingdom cohort of 1,848 treated patients followed to 2000, 38 developed the disease, with peak risk estimated 20 years after first exposure and a lifetime cumulative risk of 4.5% among those who received hormone prepared by one particular extraction method.[2] In the US programme, all 22 cases occurred among people who began treatment before a column-chromatography purification step was introduced in 1977.[6] Recombinant somatropin replaced the cadaveric product worldwide in 1985. That is the whole reason a synthetic version was pursued, and it is a documented iatrogenic catastrophe rather than a footnote.

What the research actually shows

In growth hormone deficiency, the evidence is the approval. Current US labeling for somatropin products covers pediatric growth failure due to inadequate endogenous secretion, short stature associated with Noonan syndrome and with Turner syndrome, growth failure in Prader-Willi syndrome, children born small for gestational age without catch-up growth, idiopathic short stature, and replacement in adults with growth hormone deficiency of adult or childhood onset. The largest long-term dataset is a worldwide observational registry of 15,809 growth-hormone-treated adults with confirmed deficiency, followed a mean of 5.3 years. Adverse events occurred in 51.2% and were considered treatment-related in 18.8%; de novo cancer incidence was comparable to the general population; effects on lipids and fasting glucose were neutral.[8] That is the population growth hormone was approved for, and the evidence there is real.

In healthy older adults, the effect is small and the conclusion is negative. The definitive synthesis pooled 31 articles describing 18 randomized study populations — 220 participants who received growth hormone, 107 person-years of treatment, mean age 69. Fat mass fell 2.1 kg. Lean body mass rose 2.1 kg. Weight did not change. Total cholesterol fell but not significantly after adjustment for body composition. Bone density did not change. Participants on growth hormone were significantly more likely to experience soft tissue edema, arthralgia, carpal tunnel syndrome, and gynecomastia, and somewhat more likely to develop impaired fasting glucose and diabetes. The reviewers' conclusion, stated without hedging: growth hormone cannot be recommended as an antiaging therapy.[3]

In athletes, the performance claim did not survive testing. A parallel systematic review pooled 44 articles describing 27 study samples: 303 participants who received growth hormone, 13.3 person-years, mean age 27, all physically fit. Lean body mass rose 2.1 kg. Strength and exercise capacity did not appear to improve. Exercise lactate was significantly higher on growth hormone in two of three studies that measured it. The reviewers concluded that claims growth hormone enhances physical performance are not supported by the scientific literature, and noted it may worsen exercise capacity.[4] The subsequent purpose-built randomized trial — 96 recreationally trained athletes, eight weeks of treatment, funded by the World Anti-Doping Agency — reported the same picture with one exception. Sprint capacity improved by 3.9% overall and 8.3% in men who also received testosterone. No other performance measure changed, and the sprint effect was gone six weeks after the drug stopped.[5] A 2019 review of the field places that finding in context: the lean-mass increase is largely extracellular water rather than contractile tissue, and doping with growth hormone began in the early 1980s, well before any scientific evidence of benefit.[7]

The trial that started the anti-aging story is the one most often misremembered. A 1990 study enrolled 21 healthy men aged 61 to 81 with plasma IGF-1 below 350 U/L; 12 of them received growth hormone three times a week for six months and the other 9 received nothing. In the 12 treated men, lean body mass rose 8.8 percent, adipose-tissue mass fell 14.4 percent, and lumbar vertebral bone density rose 1.6 percent. Skin thickness rose 7.1 percent, which did not reach significance (P = 0.07), and there was no significant change at the radius or proximal femur. It was small, it was six months long, it measured body composition rather than function, and everything above was published afterward and did not confirm the implication that was drawn from it.[1]

Where the evidence is weak

The approved evidence and the popular use describe different people. This is the gap that defines the page. Somatropin's randomized evidence base concerns people whose pituitary does not make enough growth hormone, treated at replacement doses titrated against laboratory monitoring. The reason most readers arrive here is anti-aging or performance use in people whose axis is normal, at doses chosen without monitoring. Those are not the same intervention, and the second one has been studied — the systematic reviews above are that study. It did not find what the reputation claims.[3][4]

Lean mass is not muscle. The single most-cited number for growth hormone in healthy people is the 2.1 kg lean-body-mass increase, and it appears in both systematic reviews. Lean body mass on dual-energy x-ray absorptiometry includes extracellular water, and growth hormone causes fluid retention — which is also the mechanism behind the edema, arthralgia, and carpal tunnel syndrome that were the most common adverse events. The randomized athlete trial that separated body cell mass from extracellular water found the lean-mass increase was driven by water, and that body cell mass rose in men only when testosterone was coadministered.[5][7]

Exposure in healthy people has been brief. A mean of 27 weeks in the elderly trials, 20 days in the athlete trials, eight weeks in the largest purpose-built athlete study. Nothing in the published randomized record follows a non-deficient person on growth hormone for years, and the reviewers of the athlete literature explicitly flag that trial regimens may not reflect the doses used outside of studies. The long-term registry that does span years enrolled only deficient adults on replacement dosing.[4][8]

The glucose signal is mechanistic, not incidental. Growth hormone opposes insulin action by design. In the healthy-elderly trials, treated participants were more likely to develop impaired fasting glucose and diabetes. In the monitored deficiency registry, glucose effects were neutral. Reading the second result as reassurance about the first is the error the two datasets invite.[3][8]

The IGF-1 exposure question is unresolved rather than settled either way. Prospective cohorts link higher circulating IGF-1 to the risk of several cancers, most consistently prostate cancer.[11][12] That work describes naturally varying levels in people taking nothing. The largest treatment registry found cancer incidence comparable to the general population, in a deficient population on replacement doses.[8] Neither speaks to what sustained supraphysiological IGF-1 does over decades, because nobody has measured it.

The historical harm is instructive about identity, not about the modern product. The cadaveric-era disasters — Creutzfeldt-Jakob disease in hundreds of recipients worldwide, and the 2024 finding of dementia and biomarker changes within the Alzheimer's phenotypic spectrum in recipients who did not die of Creutzfeldt-Jakob disease — belong to a preparation derived from human cadaver pituitary glands and discontinued in 1985.[9][10] No approved product carries that risk. What the history does establish is that what is actually inside an injectable protein preparation is a question with real consequences, and that the regulated cold chain behind an approved biologic is doing work that is invisible until it is absent.

Legal and regulatory status

Somatropin is an FDA-approved biologic, licensed under multiple biologics license applications held by different manufacturers, with the indication sets described above. Approved products are prescription-only, dispensed through a regulated supply chain, and titrated by a prescriber against IGF-1 and clinical response.[8]

Human growth hormone also carries a restriction that no other compound in this library has, and it is a statutory one rather than a regulatory one. Under section 303(e) of the Federal Food, Drug, and Cosmetic Act, distribution of human growth hormone — defined in the statute as somatrem, somatropin, or an analogue of either — for any use in humans other than the treatment of a disease or recognized medical condition authorized by the Secretary of Health and Human Services and pursuant to a physician's order, is a criminal offense carrying up to five years in prison, doubled where a person under 18 is involved. A conviction is treated as a felony violation of the Controlled Substances Act for forfeiture purposes, and the Drug Enforcement Administration is authorized to investigate. In short: distribution for anti-aging, bodybuilding, or performance purposes is restricted by statute, not merely disapproved. The authors of the 2007 systematic review state the same fact in their opening line — its use as an anti-aging therapy has not been approved and its distribution as an anti-aging agent is illegal in the United States.[3]

In tested sport the status is settled. Growth hormone is banned by the World Anti-Doping Agency as a performance-enhancing anabolic agent, prohibited at all times. Two validated detection approaches exist: the isoform method, which distinguishes injected recombinant 22-kDa hormone from the heterogeneous isoforms a pituitary secretes, and the marker method, which measures IGF-1 and the N-terminal propeptide of type III collagen. Detection rates have historically been low, which the reviewers attribute to the limitations of in-competition testing rather than to absence of use.[7]

PHL does not sell peptides, does not prescribe, and takes no position on how material reaches anyone outside the approved channel.

Questions to bring to a provider

The productive conversation about growth hormone starts by separating the two things that share the name — a treatment for a diagnosed deficiency, and an intervention in a normal axis:

  • Is there any reason to suspect growth hormone deficiency here, and what dynamic testing would establish it rather than assume it from a symptom list?[8]
  • If the goal is body composition rather than treating a deficiency, what should be expected from a systematic review that found 2.1 kg of lean mass, much of it water, and more edema and carpal tunnel syndrome?[3]
  • If the goal is athletic performance, what should be made of a randomized trial that found no change in strength, power, or maximal oxygen uptake, and a sprint effect that disappeared within six weeks?[5]
  • What baseline and follow-up glucose monitoring belongs alongside a hormone that opposes insulin action?[3]
  • Does a personal or family history of malignancy change the calculus, given the cohort associations between circulating IGF-1 and cancer risk?[12]
  • For a diagnosed deficiency, what is the plan for dose titration against IGF-1, and what adverse events would prompt a dose reduction?[8]
  • In a tested sport, what does the current prohibited list say and what detection methods are in use?[7]

A clinician who says "the evidence is excellent for a condition you may not have, and the evidence for what you are actually asking about is negative" is describing the literature accurately.

Evidence by claim

Grades describe how strong the evidence is; the line under each grade describes what kind of studies it is. How we grade evidence.

Treatment of growth hormone deficiency in adults and of defined pediatric growth disorders
Human RCT evidence human observational

This is what somatropin is approved for and where its evidence lives. Current US labeling covers pediatric growth failure from inadequate endogenous growth hormone secretion, short stature associated with Noonan syndrome, Turner syndrome, Prader-Willi syndrome, small-for-gestational-age birth without catch-up growth, and idiopathic short stature, plus replacement in adults with growth hormone deficiency of adult or childhood onset. A 15,809-patient registry followed adults on replacement for a mean of 5.3 years and supports the safety of that use as prescribed in routine practice. Approved somatropin replaces the hormone in people whose pituitary does not make enough of it, and its effectiveness does not depend on residual pituitary function.

[8]

Body composition change in healthy older adults
Human RCT evidence review

Real, small, and not the same thing as benefit. A systematic review of randomized trials in healthy elderly participants found fat mass fell by 2.1 kg and lean body mass rose by 2.1 kg, with no significant change in body weight, no change in bone density, and no durable change in lipids after adjusting for body composition. Those changes came with significantly more edema, arthralgia, carpal tunnel syndrome, and gynecomastia.

[3]

Anti-aging benefit in healthy older adults
Anecdotal reports only review

No trial supports it. The authors of the systematic review state the conclusion in one sentence: on the basis of this evidence, growth hormone cannot be recommended as an antiaging therapy. Across 18 study populations and 107 person-years of treatment, what was demonstrated was a small body-composition shift and an increased rate of adverse events. Function, healthspan, and mortality were not shown to improve, and the reviewers noted that many important outcomes were measured too infrequently to pool at all.

[3]

Improved athletic performance
Human RCT evidence review · human RCT

Tested and largely negative. A systematic review of 27 randomized study samples found lean body mass rose by 2.1 kg but strength and exercise capacity did not appear to improve, exercise lactate rose, and adverse events were more common; the reviewers concluded that claims growth hormone enhances physical performance are not supported by the scientific literature. The subsequent 96-athlete randomized trial found the same thing with one narrow exception: sprint capacity improved by 3.9% overall, an effect that did not persist six weeks after the drug stopped, while strength, power, and maximal oxygen consumption did not change. The authors of a 2019 review of the field describe the lean-mass gain as largely extracellular water rather than contractile tissue.

[4] [5] [7]

Recovery from injury or improved tissue repair in healthy people
Anecdotal reports only review

No randomized trial has evaluated it. Growth hormone acts largely through IGF-1, which stimulates whole-body protein synthesis including skeletal muscle and collagen, and that mechanistic story is the basis of the recovery reputation. Mechanism is not an outcome. Nothing in the published randomized literature reports faster healing of an injury in a person who was not growth hormone deficient.

[7]

Safety of long-term use in people who are not growth hormone deficient
Anecdotal reports only human observational · review

Unstudied. The longest controlled exposures in healthy participants ran a mean of 27 weeks in the elderly trials and 20 days in the athlete trials. The 15,809-patient long-term safety cohort is entirely a growth-hormone-deficient population on monitored replacement dosing, so it cannot be read across to supraphysiological dosing in someone whose axis is normal. There is no dataset of the second kind.

[8] [3]

Elevated IGF-1 exposure and cancer risk
Anecdotal reports only human observational

Two things are true and they are frequently conflated. Large prospective cohorts associate higher circulating IGF-1 with the risk of several cancers, most consistently prostate cancer, in people taking nothing. Separately, the largest registry of growth-hormone-treated deficient adults found de novo cancer incidence comparable to the general population. The cohort associations are about naturally varying exposure and are not a measured risk of treatment; the registry is observational, in a monitored population, on replacement doses. Neither addresses long-term supraphysiological dosing in a person with a normal axis.

[11] [12] [8]

Typical protocol range in the research

  • Randomized controlled trials of growth hormone in the healthy elderly, pooled in a systematic review of 18 study populations and 220 treated participants, treated for a mean of 27 weeks

    A mean initial daily dose of about 14 micrograms per kilogram of body weight, with wide variation across the included trials [3]

  • Randomized controlled trials of growth hormone in physically fit young adults, pooled in a systematic review of 27 study samples and 303 treated participants, treated for a mean of 20 days

    A mean of about 36 micrograms per kilogram of body weight per day — roughly two and a half times the dose used in the elderly trials, and still, in the reviewers' own words, possibly lower than what is used outside of studies [4]

  • Randomized, placebo-controlled trial of 96 recreationally trained athletes, 8 weeks of treatment followed by a 6-week washout, funded by the World Anti-Doping Agency

    2 mg per day subcutaneously in men and in women, with a separate male arm receiving 250 mg of testosterone weekly alongside it [5]

The three research ranges above come from trials in healthy people, which is exactly the population the approved labeling does not cover, and the reviewers of the athlete literature note that trial regimens may not reflect what is used outside of studies. Approved labeling is deliberately not reproduced as a range here: labeled schedules are weight-based or fixed low starting doses titrated upward by the prescriber against IGF-1 concentration, clinical response, and side effects, and they differ by product, by indication, and by patient age. They belong to the prescriber who dispensed them and to the labeling dispensed with the product. No published trial establishes a dose of growth hormone for anti-aging or performance purposes, because no published trial supports those uses at all.

Ranges are what published research reports, not a recommendation. PHL does not prescribe, and nothing here is personalized to you.

Side effects & safety signals

  • Soft tissue edema, arthralgia, carpal tunnel syndrome, and gynecomastia

    Significantly more common on growth hormone than without it in the randomized trials pooled from healthy elderly participants, and soft tissue edema and fatigue were significantly more common in the athlete trials. · These are the dose-limiting effects in practice and the reason trials in healthy people had discontinuations. They are largely fluid-retention phenomena and largely reversible on dose reduction or withdrawal, which does not make them trivial: carpal tunnel syndrome is a nerve compression injury.

    [3] [4]

  • Impaired fasting glucose and new-onset diabetes mellitus

    Participants treated with growth hormone in the healthy-elderly trials were somewhat more likely to develop impaired fasting glucose and diabetes mellitus than those who were not. · Growth hormone is a counter-regulatory hormone that directly opposes insulin action, so this is a mechanistic consequence rather than an idiosyncratic reaction. In the deficiency population, where treatment is dose-titrated against laboratory monitoring, the large observational safety cohort found neutral effects on fasting blood glucose — a difference that says something about monitored replacement dosing versus supraphysiological dosing in people whose axis was already normal. Existing diabetes, prediabetes, or use of any glucose-lowering medication is a provider-discussion flag.

    [3] [8]

  • Reduced exercise capacity and higher exercise lactate

    Lactate levels during exercise were significantly higher on growth hormone in two of the three trials that measured it. · This is the opposite of the intended effect and it is the most counterintuitive finding in the athlete literature. The systematic reviewers concluded that growth hormone may worsen exercise capacity rather than improve it, and the single largest randomized athlete trial found no improvement in strength, power, or maximal oxygen consumption.

    [4] [5]

  • Transmissible neurodegenerative disease from cadaveric pituitary-derived preparations, historical

    In a United Kingdom cohort of 1,848 patients treated between 1959 and 1985, 38 developed Creutzfeldt-Jakob disease; the estimated lifetime cumulative risk in those treated with hormone prepared by one particular extraction method was 4.5%. In the US National Hormone and Pituitary Program cohort of 5,570 recipients, all 22 cases occurred in the 2,099 people treated before 1977. · Fatal, and with a latency measured in decades — the peak risk in the UK cohort was estimated at 20 years after first exposure. This is the documented iatrogenic-harm history of a preparation derived from human cadaver pituitary glands, superseded worldwide by recombinant manufacture in 1985. It is a historical entry and not a risk of any approved product today; it is on this page because the history explains why the modern product exists and why identity of material matters.

    [2] [6]

  • Amyloid-beta transmission in the same historical cohorts

    Described in a 2024 case series of recipients who did not die of Creutzfeldt-Jakob disease. · Recipients of cadaveric pituitary-derived growth hormone who survived long enough developed dementia and biomarker changes within the phenotypic spectrum of Alzheimer's disease, which the authors interpret as an environmentally acquired form of the condition. The same authors state there is no suggestion that amyloid-beta is transmitted between people in the activities of daily life. Again historical, again about a preparation no longer made, and again the reason identity of injectable material is not an abstract concern.

    [9] [10]

  • Long-term safety in the deficiency population, where it has actually been followed

    Adverse events were reported in 51.2% of 15,809 growth-hormone-treated adults with growth hormone deficiency followed for a mean of 5.3 years, considered treatment-related in 18.8%. · This is the largest long-term dataset that exists, and it is reassuring on its own terms: overall de novo cancer incidence was comparable to the general population, and adverse-event rates did not correlate with dose after adjustment. It is also an observational registry in a monitored deficiency population on replacement dosing, which is not the population or the dosing that most readers arrive at this page thinking about.

    [8]

Published lists are never exhaustive, so report anything unexpected to a licensed provider.

Storage, handling & reconstitution

Lyophilized storage
Approved somatropin products are supplied in several presentations — lyophilized powder in a vial or cartridge, and ready-to-use solution in a prefilled pen — and their storage requirements are not interchangeable. Each carries a manufacturer stability programme, an expiry date, and specific refrigeration requirements printed on the labeling dispensed with the prescription. That labeling is the source, and it is presentation-specific; no general rule covers all somatropin products.
Reconstituted storage
Once a powdered presentation is mixed, or a pen is first used, approved labeling assigns a limited in-use period during which the product is kept refrigerated and protected from light. The number of days differs between products and even between presentations of the same product. The prescription labeling and the dispensing pharmacist are where that number comes from.
Reconstitution diluent
Powdered presentations of approved somatropin are reconstituted with the diluent supplied in the package, which differs by product — sterile water for injection for some, a bacteriostatic or preserved diluent for others. Prefilled-solution presentations are not reconstituted at all. Substituting a diluent changes the labeled in-use period, so this is not an interchangeable detail.
Reconstitution & handling
Approved labeling directs gentle mixing rather than shaking, and directs inspection of the resulting solution before use. Beyond that, the preparation steps for an approved biologic come from the labeling dispensed with the prescription and from the pharmacist, both of which are specific to the product and presentation. PHL publishes no volume or unit calculations, because those are dosing decisions and dosing decisions belong with a licensed clinician.
Handling notes
Somatropin is an approved biologic with a regulated cold chain behind it, which is a categorical difference from the research compounds elsewhere in this library. It is also the reason material bearing the name outside that chain has no stability information at all: no manufacturer standard, no assigned expiry, no lot testing. The published analytical and anti-doping literature exists in part because determining what is actually in such material requires laboratory work.

The how-to guides cover the conventions behind these fields, and what the published stability data does and does not establish: Storage, Reconstitution, Handling.

Questions for your provider

Bring this page to a licensed provider. A provider can order labs, review your medications and history, and tell you whether anything here is relevant to your situation. This page can't. Peptide Health Lab does not prescribe and does not sell peptides.

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Citations

12 sources · every identifier checked against PubMed

Before you act on any of this

This page is educational only and is not medical advice. It does not diagnose, treat, or prescribe. Review it with a licensed provider before making any health decision. Peptide Health Lab does not sell peptides.

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