Growth-hormone peptides for transmasc people who want muscle

Draft · intended for 2026-05-06

Day _ of writing daily.

This is the post I promised in Masculinizing HRT when I said "there are many peptides and steroids that can increase muscle growth, but often at the cost of also increasing health risks and cancer risks. I will probably do a separate post on this at some point." This is the peptides half of that promise — specifically the growth-hormone axis. The steroids half (testosterone above-replacement, nandrolone, oxandrolone, the rest) is a separate conversation and I'll do that one later.

Standard caveat from the masculinizing post still stands: I'm not transmasc and I'm working from the literature rather than from lived experience or a clinic patient panel. If you've actually run any of these and your read disagrees with mine, please tell me — most of what I'm pushing back on here is community lore that hasn't been seriously challenged in writing.

The honest one-line summary: testosterone already does most of what GH peptides claim to do, the only adult RCT in the entire secretagogue class with a clean lean-mass number gives you about 1 kg of fat-free mass per year with no strength gain, and the rest of the class has no contemporary efficacy RCT in adults at all.

The rest of the post is why.

What the GH axis actually is

The hypothalamus releases GHRH, which makes the pituitary release growth hormone in pulses, which goes to the liver, which makes IGF-1, which goes to muscle and bone and most other tissues. There's also ghrelin, which the stomach releases when you're hungry, and which independently makes the pituitary release GH via a different receptor (GHS-R1a). And there's somatostatin, which is the brake — it stops the pituitary from secreting too much GH. Most of the drugs in this post hit one of those four levers.

The thing that matters for the rest of the post: testosterone also raises hepatic IGF-1 directly. If you're on a typical transmasc T regimen with serum levels in the upper male range, your IGF-1 is already elevated relative to your pre-T baseline. Most published trans-T cohort data shows IGF-1 going up alongside T, and this is one of the reasons T causes lean mass to increase even without lifting. So when a peptide clinic says "this peptide will raise your IGF-1 and help you build muscle" — your IGF-1 is already raised. The marginal headroom is smaller than the marketing implies.

The other thing: oral estrogen (and high-dose sublingual) blunts hepatic IGF-1 by 20–40% via first-pass effect. Transdermal and injectable estradiol don't. This matters less for transmasc readers, but it's why the Endocrine Society hypopituitarism guidelines explicitly favor transdermal estradiol when GH replacement is concurrent. If you ever swing back to a feminizing or non-binary regimen and you're stacking peptides, this is one of the things that will tank your numbers.

The whole list

Comparator baseline:

GHRH analogues (push the pituitary):

GH secretagogues / ghrelin agonists (push via GHS-R1a):

Direct IGF-axis:

I'll go through these in roughly descending order of "how much real human evidence supports the muscle claim."

Tesamorelin: actually FDA-approved, but not what you want

Tesamorelin is the only drug in this whole list with a clean modern RCT that produces a reproducible body-comp number in a defined adult population. Falutz et al. NEJM 2007 (LIPO-010) randomized 412 HIV patients with central lipohypertrophy and showed visceral adipose tissue dropping 15.2% versus placebo gaining 5.0% at 26 weeks. Triglycerides dropped about 50 mg/dL. Subcutaneous fat and BMI didn't significantly change.

The thing that gets missed in the looksmax discourse is that that's the entire effect. Tesamorelin redistributes fat (visceral down, subcutaneous unchanged) and that's it. It does not produce meaningful lean-mass gain in non-deficient adults. In Stanley et al. Lancet HIV 2019, tesamorelin in HIV patients with NAFLD reduced hepatic fat fraction by about 4 percentage points (37% relative) at 12 months and 35% of treated patients no longer met NAFLD criteria — also a fat-redistribution result, not a muscle result.

So if you're a transmasc reader and what you want is to put muscle on your frame, tesamorelin is the wrong drug. If on the other hand you've been on T for a while, your body comp has shifted in the masculine direction (which generally means more visceral fat at any given total body fat percentage), and you want to specifically reduce visceral fat — tesamorelin has the cleanest evidence in the class. But for "I want bigger biceps" purposes, this isn't it.

Also worth noting: brand cost is in the $2,400–2,800/month range with insurance gating to the HIV indication. Compounded 503B alternatives are $200–450/month with variable quality. Pregnancy contraindication (rat hydrocephaly), active malignancy contraindication, and a documented diabetes signal in the LIPO trials (HR 3.3 for new HbA1c ≥6.5% versus placebo). Off-label use does not inherit "FDA-approved is safe" status.

MK-677: the only secretagogue with a real long-term RCT

If you want a peptide-style intervention that actually has long-term controlled human data for body composition, MK-677 is the only one. Nass et al. 2008 (Annals of Internal Medicine) randomized 65 older adults to 25 mg oral MK-677 daily versus placebo for 12 months. Fat-free mass went up about 1.1 kg in the MK-677 group versus essentially no change on placebo. IGF-1 rose to mid-young-adult range. Strength didn't improve. Function didn't improve. Fasting glucose went up about 5 mg/dL and HbA1c rose modestly.

A kilogram of fat-free mass per year, with no strength gain, in older adults. Translate that to a transmasc reader on T who is already gaining lean mass from the T itself: you're stacking maybe a kilo a year on top of what you'd get anyway, and you're getting it without strength improvement. You might genuinely value that — appearance gain without any other benefit is a real thing — but it's a much smaller lever than the marketing implies.

The bigger problem is Adunsky et al. 2011, the MK-677 hip-fracture recovery RCT. The trial was halted early because of a congestive heart failure imbalance: 4 cases on MK-677 versus 1 on placebo. The investigators were appropriately careful about inferring causation from such small numbers, but Merck didn't pursue an indication after this, and the signal is the most consequential adverse-event finding in the entire secretagogue class. Peptide-clinic marketing for MK-677 routinely doesn't mention it.

The other things to know about MK-677 that the marketing tends to underplay: appetite stimulation is real and dose-dependent (this is what ghrelin does — your stomach is telling your brain you're hungry). Edema and water retention are class effects. The diabetes-direction signal is real even if it's not enough to be a hard contraindication for healthy adults. There's a sleep effect that's actually well-documented — Copinschi 1997 showed about 50% increase in stage 4 slow-wave sleep and 20% increase in REM in healthy young men over a week of dosing — and this is the most defensible non-body-comp claim for MK-677. Whether it persists for months hasn't been studied.

So: the practical math for a transmasc lean-mass goal is roughly +1 kg/year in fat-free mass without strength, +5 mg/dL fasting glucose, increased appetite (which makes the eating-enough-to-grow side easier but also makes a clean lean-bulk harder), water retention, and a small but real CHF signal in older patients. You can argue this is worth it. You should be honest that it's a modest effect, not a transformative one.

WADA-prohibited under category S2. Not FDA-approved for anything. Not on the FDA's 503A bulks list as of the most recent listing checked, although that status is in flux as of early 2026.

Sermorelin, CJC-1295, ipamorelin, GHRP-2/6, hexarelin: the "no contemporary RCT" tier

This is the bulk of the peptide-clinic menu, and it's the part where the gap between marketing and evidence is widest.

Sermorelin's branded product (GEREF, NDA 020443) was withdrawn in 2009 for commercial reasons (not safety). All adult anti-aging and body-composition claims are extrapolated from somatropin and from uncontrolled clinic experience. There is no contemporary RCT in healthy adults that I could find supporting any specific effect size on body composition or muscle. Compounding eligibility under 503A has been preserved, but whether the FDA preserves that at the next PCAC review is genuinely uncertain.

CJC-1295 comes in two flavors. "No DAC" is modified GRF 1–29 with four amino acid substitutions for stability and a roughly 30-minute half-life — used because the parent peptide degrades too fast. "With DAC" adds a maleimidopropionic acid linker that covalently binds serum albumin in vivo, extending the half-life to 6–8 days. Teichman et al. JCEM 2006 showed a single CJC-DAC injection elevates GH 2–10x for 6+ days and IGF-1 0.5–3x for 9–11 days in healthy volunteers. After that paper, ConjuChem ran a phase 2 lipodystrophy program with CJC-DAC, and the program was halted in 2006 after a participant death — most likely unrelated to study drug per the attending physician at the time, but development never resumed. There has been no contemporary phase 2 or 3 efficacy RCT for either form. Adult body-composition, sleep, and anti-aging claims rest on mechanism plus community anecdote.

Ipamorelin is the GHRP that's marketed as side-effect-free because it's selective for GHS-R1a and doesn't elevate cortisol or prolactin much in animal pharmacology. The selectivity claim is partially real. The "side-effect-free" claim is materially overstated. The only well-conducted human RCT of ipamorelin (postoperative ileus phase 2, NCT00672074) failed efficacy, and Helsinn discontinued the program. There is no human trial showing ipamorelin produces lean mass gain, sleep improvement, or any of the anti-aging endpoints that the peptide-clinic literature claims for it.

GHRP-2 has a single national approval — PMDA in Japan, October 2004, and only as a single-dose IV diagnostic for GHD. Not therapeutic. GHRP-6 and hexarelin have no approval anywhere. None of the three has a controlled human trial supporting chronic-dose body composition, sleep, or anti-aging claims. Hexarelin actually reduces slow-wave sleep (the opposite of MK-677) and shows tachyphylaxis — the GH response declines with repeated dosing. All three raise cortisol, ACTH, and prolactin alongside GH (in contrast to ipamorelin), which is the pharmacological reason chronic dosing is concerning in a way "you're just nudging your own pituitary" framing doesn't capture.

I want to be clear about what I mean by "no contemporary RCT." There are old pharmacology papers for these from the 1990s — single-dose acute GH-response studies in healthy volunteers, mostly run as part of mechanism work or as pharmacokinetic submissions for failed drug-development programs. There aren't randomized placebo-controlled trials over weeks-to-months in healthy adults with body-composition endpoints. That's the relevant kind of evidence for the claims being sold, and it isn't there.

IGF-1 LR3 and IGF-1 DES: research-chem only, do not use without thinking very hard

These are direct IGF-1 analogues with reduced binding to IGFBPs (the carrier proteins), which extends half-life and gives flatter sustained IGF-1 levels. IGF-1 LR3's half-life is somewhere in the 20–30 hour range. There is no human RCT for either compound for any indication. Bodybuilding dosing (typically 20–100 mcg/day for IGF-1 LR3) is derived from veterinary literature and animal physiology, not human studies.

The acute risk worth flagging: IGF-1 cross-activates the insulin receptor at high doses, so hypoglycemia is a real and reported adverse event. The chronic risk is what gets pushed under the rug — flat sustained IGF-1 elevation is the closest thing in this list to chemical acromegaly, and it has the cleanest biological connection to the cancer risk argument I'll come back to in the next section. Mecasermin rinfabate (Iplex) was the only branded long-acting IGF-1 product and it was withdrawn from the US market in 2007 after a Tercica/Genentech legal dispute; it's not currently available.

I'm explicit about this one because it's the part of the GH-axis space where the gap between "what bodybuilders use" and "what has been seriously studied in humans" is largest. There is no controlled human dose-response data for IGF-1 LR3. The community dosing protocols are not clinical knowledge.

How this stacks up against what actually builds muscle

Comparator framing matters here because you can run the deepest peptide stack in the world and still lose to a transmasc person who eats enough protein and runs a serious lifting program.

T plus lifting plus protein plus sleep, in someone trained. Endogenous T in the upper male range plus a structured progressive resistance program plus 1.6–2.2 g/kg/day protein plus adequate sleep is the boring version of this answer. The trans-T body-comp literature shows lean mass increasing 3–7 kg over the first 1–2 years of T even without deliberate training (numbers vary across Wierckx 2014, Klaver 2017, and the Spack/Tangpricha follow-ups). Add deliberate training and the gap to "what GH peptides offer" widens.

Anabolic steroids above replacement. Bhasin et al. 1996 NEJM — the foundational testosterone-supraphysiologic-dose study — showed about 6.1 kg fat-free mass gain on 600 mg/week testosterone enanthate plus exercise versus 1.9 kg on T+exercise at replacement-equivalent dosing, in 10 weeks. That is multiple times what MK-677 produces in a year, and it's just T at a different dose. Nandrolone, oxandrolone, and the full AAS list have their own evidence base. They have their own risk profile, which is real. But the relevant point for this post is: the peptide ecosystem markets itself as "almost like steroids without the risks," and the actual effect-size data say it's much further from steroids than the marketing implies, while the risk profile is not zero.

(Steroids are a separate post. I'm not going to do that here.)

GLP-1 / GIP for fat loss. Not relevant for the lean-mass question, but worth flagging because peptide clinics often sell GH peptides for "recomp" purposes that GLP-1/GIP would do better. Tirzepatide produced about −21% body weight at 72 weeks in SURMOUNT-1. Semaglutide produced about −15% at 68 weeks in STEP 1. No GH-axis intervention reaches double-digit total weight loss, and tesamorelin only redistributes fat without reducing total weight. If your actual goal is leaner-while-keeping-mass and you have body fat to lose, the boring answer is GLP-1/GIP plus a structured cut, not GH peptides.

So the realistic position for a transmasc reader who wants muscle is: the upside from T is much larger than the upside from any of these peptides, the upside from a serious lifting program is much larger than the upside from the peptides, and the upside from above-replacement T (with attendant risks) is much larger than the upside from the peptides. GH peptides are at best a small additive on top of all of those. And in MK-677's case, you're paying the additive in fasting glucose and a small CHF signal.

The cancer / IGF-1 risk thing

This is the part that almost never makes it into peptide-clinic marketing and that I think is the most consequential point in the whole post.

The cancer-and-mortality data on IGF-1 form a specific shape. Murphy et al. Annals of Oncology 2020, a Mendelian randomization analysis using genetic instruments in roughly 430,000 women, links genetically-elevated IGF-1 to higher breast cancer risk. Travis et al. International Journal of Cancer 2016 does the same for high-grade prostate cancer. The Guevara-Aguirre Ecuadorian Laron syndrome cohort — adults with effectively zero lifelong IGF-1 because of GH receptor mutations — has about 1% lifetime cancer mortality versus ~20% in their unaffected relatives.

The all-cause mortality picture is U-shaped — both very low and very high IGF-1 are associated with higher mortality, and mid-range is the sweet spot (Rahmani et al. 2022 meta-analysis). The SAGhE long-term cohort of about 24,000 patients followed for >400,000 patient-years after childhood somatropin treatment showed reassuring all-cause mortality in low-risk diagnostic groups (isolated GHD, ISS) but elevated cause-specific circulatory and haematological mortality across all risk strata.

Read together: on-label, dose-titrated GH replacement in adults with confirmed GHD is broadly safe, and the regulatory framework around it exists for a reason. Chronic supraphysiologic IGF-1 push in a healthy adult — which is what years of CJC-1295/ipamorelin, MK-677, or IGF-1 LR3 looks like at typical community doses — is not the same risk profile. The peptide-clinic ecosystem cannot rule out a real cancer-direction risk because the trials needed to rule it out don't exist.

This matters more than usual for a transmasc reader because:

  1. T already raises hepatic IGF-1 baseline. Adding peptides on top pushes you further along the IGF-1 axis.
  2. The transmasc demographic skews young, which means the relevant exposure window is decades, not years.
  3. Most of the cancer endpoints in the IGF-1 literature have a long latency. You don't see the consequences of pushing IGF-1 in your 20s until your 40s and 50s.
  4. The Mendelian randomization signal on prostate cancer is specifically high-grade prostate cancer, which is relevant for transmasc readers who've kept their prostate.

I don't think this means "no transmasc person should ever use any of these." I think it means the looksmax/longevity framing of "raising IGF-1 is good for you" inverts the direction of the strongest controlled evidence, and the risk is high enough to matter when you're talking about decades of exposure.

Acromegaly-direction features (and why this is different for you)

The classic looksmax claim is that GH peptides will give you a bigger jaw, larger hands, and a more rugged face. This is true at chronic supraphysiologic doses — that's literally what acromegaly is — but it's false at typical secretagogue doses. Soft-tissue facial swelling from fluid retention is documented and reversible at MK-677 and CJC-DAC doses; bony feature change is not.

The bigger thing: acromegaly is a disease. The feature change comes packaged with cardiac hypertrophy (acromegalic cardiomyopathy is a recognized entity, with LV mass typically increased and progressing to heart failure if untreated), insulin resistance progressing to diabetes in most patients, sleep apnea, organomegaly, joint changes, and approximately 10 years reduced life expectancy if untreated. Reaching the feature endpoint via supraphysiologic GH abuse — which is what bodybuilding-pattern GH dosing produces — gets you the cardiomyopathy and the diabetes and the organomegaly along with the jaw and the hands.

For a transmasc reader specifically: yes, masculine direction is what you want. No, "low-grade chemical acromegaly" is not a sensible way to get it. Bone change of a magnitude visible on a face takes years and a level of IGF-1 elevation that gives you the rest of the package too. The realistic path to a more masculine face structure is FFS (or its masculinizing equivalent — there isn't a great body of literature on this and I'd want to do a separate post), targeted lift hypertrophy of the neck/traps/shoulders, beard density work, and time on T. Not GH peptides.

Research-chem reality, vendor purity, and FDA enforcement

Most of the GH peptides in this post — sermorelin aside, sometimes — aren't legally available as approved drugs in the US for body-composition use. They get sold as "research chemicals" by peptide vendors. The actual product quality is variable in ways that the community discourse tends to minimize.

Independent purity analyses I could find for peptide-vendor products show a wide range — somewhere in the 5–75% purity range across various analyses, with vendor Certificates of Analysis frequently at odds with third-party HPLC and mass-spec results. There are documented cases of products labeled as one peptide containing a different peptide, products that are the right peptide at much lower-than-stated dose, and products contaminated with bacterial endotoxin from poor sterility practices.

FDA enforcement has stepped up. October 2023 warning letters and December 2024 follow-ups went to peptide vendors marketing unapproved drugs (sermorelin, retatrutide, cagrilintide, semaglutide, tirzepatide products) under "research only" labeling. The FDA has explicitly rejected the "research only / not for human consumption" defense when the marketing context shows directed-to-human-use intent. The 503A compounding pathway for these peptides is in flux as of early 2026 — HHS made a policy-intent announcement in February 2026 about reclassifying several of the named peptides; that hasn't translated to final rulemaking and the practical compounding landscape in 6–12 months is genuinely unpredictable.

WADA-prohibited (category S2 — peptide hormones, growth factors, related substances and mimetics). If you're competing in any sport that's WADA-tested, all of these are banned including MK-677 and tesamorelin. This is rarely the binding constraint for a transmasc reader on T already (because T itself gets you banned from most sport categories anyway), but it's worth knowing.

What I would actually do

Speaking to a hypothetical transmasc reader who came in saying "I want muscle, what do I do":

  1. If you're not yet on T or you've been on it less than a year, the answer is mostly wait. T is doing 70–80% of the lean-mass work, and the trajectory of body-comp change on T is multi-year. Layering peptides on top in year 1 is wasted spend.
  2. If you're not lifting seriously (3–5x/week, structured progression, eating enough), fix that before anything else. There is no peptide whose effect size touches "actually train and eat enough."
  3. If you're doing all of that and want more, the two honest options are:
    • Above-replacement T or other AAS, which is a real choice with real tradeoffs and a separate post.
    • Some additive intervention with smaller upside.
  4. If the second option is what you want, MK-677 has the only real evidence base for lean-mass gain in adults. The effect is modest (~1 kg/year FFM, no strength gain). The cost is appetite, water retention, modestly worsened glucose, and the unresolved CHF signal from Adunsky 2011. WADA-banned.
  5. If you have a specific visceral-fat problem on T (which can happen — T can shift fat distribution masculine-ward, including visceral, even when total body fat is stable), tesamorelin has the cleanest evidence in the class but it costs $200–2,800/month depending on source and isn't a muscle drug.
  6. Sermorelin, CJC-1295, ipamorelin, GHRP-2/6, hexarelin, IGF-1 LR3, IGF-1 DES — I'd avoid for body composition until someone shows me a contemporary adult RCT. The peptide-clinic stack of "CJC + ipamorelin" is the canonical example of a regimen sold confidently with no efficacy RCT in adults behind it.
  7. Across all of the above, the cancer/IGF-1 risk argument is the thing that should weigh most for a young transmasc reader thinking about decades of exposure. Pushing IGF-1 chronically is not nothing, even if the secretagogues feel safer than direct IGF-1 because the somatostatin loop is intact at typical doses.

Things I'm less sure about

The trans-specific interaction picture is mostly extrapolated from cis male and cis female literature plus mechanism. There isn't a meaningful trans cohort study of MK-677 or any of the secretagogues that I found. So when I say "T already amplifies IGF-1 so the marginal headroom is smaller" — that's mechanistically correct, but I don't have a published number for "MK-677 effect on top of T" specifically.

I'm also less sure about the Adunsky CHF imbalance. Four versus one in a small trial is the kind of signal that could be a real drug effect or could be noise that randomly broke the wrong way. The reason I'm willing to flag it is that Merck didn't pursue an indication afterwards and the secretagogue class is biologically positioned for cardiac concerns (acromegalic cardiomyopathy is the upper-end version of the same physiology). But "MK-677 causes heart failure" is not what the data say. "There's an unresolved signal worth knowing about" is.

The 503A compounding picture for these peptides is a moving target as of early 2026 and the post may be wrong on specifics by the time anyone is reading it. The general shape — peptides marketed as research chemicals, FDA stepping up enforcement, compounding eligibility under review — is durable; the specifics are not.

If you've actually run any of these long-term as a transmasc person and your read disagrees with mine, please tell me. The community evidence base for "what these actually do on top of T" is thinner than the marketing implies, and one careful self-report is worth more than another round of peptide-clinic copy.

The detailed evidence map with all 32 claim files and sources is at research/hgh-analogues/ in the wiki repo for anyone who wants the receipts.