GHRH (1-29) vs Ipamorelin
The 29-amino-acid fragment of growth hormone-releasing hormone, and the shortest piece of it with full activity. Approved in 1997 as Geref for growth failure in children with growth hormone deficiency and discontinued in 2008; the one controlled trial in older adults tested a modified version of the molecule, not this one [1][5][7].
A uniquely selective growth hormone booster that tells your pituitary to release more GH without messing with your cortisol or other hormones—making it the 'clean' choice among growth hormone peptides.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
GHRH (1-29)
30–30 mcg/kg/day
Ipamorelin
200–200 mcg
Frequency
GHRH (1-29)
Once daily at bedtime
Ipamorelin
Multiple times daily
Administration
GHRH (1-29)
Subcutaneous injection
Ipamorelin
Subcutaneous injection
Cycle length
GHRH (1-29)
Continuous — the label treats until the growth plates fuse
Ipamorelin
8-12 weeks
Onset speed
GHRH (1-29)
Height velocity measurable at 6 months in children; nothing established in adults
Ipamorelin
Moderate (1-2 weeks)
Evidence level
GHRH (1-29)
Human trials in children; one 19-person adult trial of a modified analogue
Ipamorelin
Moderate human trials (Phase 1-2)
Benefit ratings
Growth and Development
Body Composition
Performance and Recovery
GH Selectivity
Recovery Support
Safety Profile
Compound specifications
GHRH (1-29)
Molecular formula
C149H246N44O42S
Molecular weight
3357.9 g/mol
Half-life
~10-20 minutes
Bioavailability
Subcutaneous: moderate; Intranasal: 3-5%
CAS number
86168-78-7
Ipamorelin
Molecular formula
C38H49N9O5
Molecular weight
711.85 g/mol
Half-life
2 hours
Bioavailability
High when injected subcutaneously
CAS number
170851-70-4
Dosing compared
GHRH (1-29)
Subcutaneous
30 mcg/kg/day
Once daily at bedtime · Continuous — trials ran 12 months; the label treats until the growth plates fuse
The approved Geref dose and the only dose of this molecule tested once daily: 30 mcg/kg (0.03 mg/kg) subcutaneously at bedtime in prepubertal children with growth hormone deficiency. In the 110-child pivotal trial it raised height velocity from 4.1 to 8.0 cm/year at 6 months [5]. The same 30 mcg/kg total has also been given as 15 mcg/kg TWICE daily in children with radiation-induced deficiency [6]. Two things this dose is not: it is not an adult dose — no trial has given sermorelin at 30 mcg/kg to adults, and for a 75 kg adult it would be 2,250 mcg — and it is not equivalent to growth hormone, which produced larger height gains at the same microgram-per-kilogram dose [1].
10 mcg/kg/day
Once nightly · 16 weeks in the only controlled adult trial
Read the molecule before you read the number. The only controlled trial in older adults used [Nle27]GHRH-(1-29)-NH2 — a norleucine-27 analogue, not sermorelin — at 10 mcg/kg nightly for 16 weeks in 19 people aged 55 to 71 [7][8]. That is roughly 750 mcg for a 75 kg adult. GH and IGF-I rose, but IGF-I drifted back toward baseline by week 16; lean mass, insulin sensitivity, well-being and libido improved in men only; body fat and bone density did not change in either sex; sleep was unaffected [7]. The fixed 200-300 mcg nightly figure that circulates for adults is community practice — it appears in no trial and on no label, and it is 3 to 4 times below this studied dose. It is listed here because people use it, not because it has evidence behind it.
Ipamorelin
Subcutaneous
100 mcg per injection
2-3 times daily · 4-8 weeks
Conservative entry dose; Ipamorelin is a selective GH secretagogue with a ~2 hour half-life, so doses are split through the day [1][2]. Used in research and practice to assess tolerance before titrating up.
200 mcg per injection
2-3 times daily · 8-12 weeks
Most commonly cited research/practice dose; gives a meaningful pulsatile GH release without raising cortisol or prolactin at standard doses [1][2].
300 mcg per injection
3 times daily · 8-12 weeks
Upper end of the commonly used range; total daily exposure split across three injections. Used in practice by experienced users [1].
Best suited for
GHRH (1-29)
Helping Kids Catch Up in Height
Children with growth hormone deficiency grow slowly because the signal to release growth hormone is weak. GHRH(1-29) supplies that signal. In the 110-child trial behind the approval, 30 mcg/kg at bedtime nearly doubled height velocity in the first 6 months, and bone age advanced in step with height rather than racing ahead of it [5]. It is also fair to say that growth hormone itself worked better, which is part of why this product left the market [1].
Testing for Growth Problems
A single intravenous dose of 1 mcg/kg is a rapid and relatively specific test of whether the pituitary can release growth hormone, and it produces fewer false positives in children without deficiency than other provocative tests. A normal response does not rule deficiency out, though — a hypothalamic cause can pass this test, so it is used alongside conventional testing rather than instead of it [1].
Adults — what is actually known
GHRH works upstream: it asks the pituitary to release its own growth hormone rather than replacing the hormone, so the body's feedback loops stay in the circuit. That is a real mechanical difference from injecting growth hormone. What it has not been shown to do is change how adults look or perform. The only controlled adult trial ran 16 weeks in 19 people aged 55-71, used a modified version of the molecule, and found lean mass and well-being improved in men but not women, with no change in body fat [7][8]. No trial has tested sermorelin itself in healthy adults.
Ipamorelin
Clean GH Boost Seekers
If you want the benefits of increased growth hormone without spiking cortisol or other stress hormones, Ipamorelin is uniquely selective. Unlike GHRP-2 or GHRP-6, it won't raise your cortisol levels even at doses 200 times higher than needed for GH release.
Recovery-Focused Athletes
Ipamorelin shines for athletes who want better recovery between training sessions. The GH boost helps repair muscle tissue faster, and since it doesn't mess with other hormones, you can use it consistently without the rollercoaster effects.
Anti-Aging Enthusiasts
Growth hormone naturally declines as we age, contributing to muscle loss, fat gain, and reduced vitality. Ipamorelin offers a gentle way to restore more youthful GH levels without the risks of actual HGH therapy.
Those Recovering from Steroid Use
Research shows Ipamorelin can help counteract the muscle and bone-weakening effects of glucocorticoid medications. If you've been on steroids for medical reasons, this peptide may help you rebuild what you've lost.
Side effects
GHRH (1-29)
Common
- Transient facial flushing
- Injection site reaction
Uncommon
- Hypothyroidism
- Anti-GRF antibodies
- Transient raised blood lipids
Serious
- Hypersensitivity reaction
Ipamorelin
Common
- Mild headache
- Injection site reactions
- Water retention
- Increased appetite
Uncommon
- Tingling in hands or feet
- Joint stiffness
Serious
- Allergic reaction
Safety & evidence
GHRH (1-29)
Evidence level
Human trials in children; one 19-person adult trial of a modified analogue
FDA status
Approved 1997 as Geref for growth failure in children with growth hormone deficiency; discontinued by the manufacturer in July 2008 and no longer marketed in the US. FDA determined in 2013 it was not withdrawn for safety or effectiveness reasons. Sermorelin sold today is compounded, not an FDA-approved product.
Safety overview
The largest safety dataset is the 110-child pivotal trial, where 30 mcg/kg/day for up to a year produced no adverse changes in general biochemical or hormonal analyses, no change in fasting glucose, and no excessive IGF-I generation [5]. Across the paediatric programme the most commonly reported adverse events were transient facial flushing and pain at the injection site [1]. The Geref prescribing information puts numbers on that: an injection reaction — pain, swelling or redness — in about 1 patient in 6, with 3 of 350 exposed patients discontinuing because of it; hypothyroidism in 6.5% during therapy, which is why the label requires thyroid testing before and during treatment; and anti-GRF antibodies in a large proportion of patients at least once during treatment, of unclear significance and with no apparent effect on growth. In the 19-adult trial of the norleucine-27 analogue the only adverse effect was transient hyperlipidaemia, which resolved by the end of the study [7], and the companion immune paper reported no adverse effects [8].
Contraindications
- Known hypersensitivity to sermorelin or any excipient
- Closed growth plates, if the goal is height — the label stops treatment once the epiphyses fuse
- Pregnancy and breastfeeding — no human data
Ipamorelin
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Ipamorelin's main selling point is that it raises growth hormone without raising cortisol or ACTH — two stress hormones that similar peptides do raise. That was shown in pigs, and it held even at doses more than 200 times higher than the amount needed to raise growth hormone [1]. It has not been checked in people. The two published human studies measured ipamorelin and growth hormone only; neither one assayed cortisol, ACTH or prolactin [2][3]. Most of what we know about safety in people comes from a single trial in patients recovering from bowel surgery. 114 people took part: 56 got ipamorelin through an IV for up to seven days, and 58 got a placebo. Most side effects were mild to moderate, and were the kind you would expect after surgery [3]. Serious problems happened at about the same rate in both groups — roughly 1 in 6 either way (17.9% on ipamorelin, 15.5% on placebo). But three things were more common on ipamorelin: low potassium in about 1 in 8 people versus about 1 in 30 on placebo (12.5% vs 3.4%), trouble sleeping in about 1 in 9 versus about 1 in 19 (10.7% vs 5.2%), and high blood sugar at discharge in about 1 in 7 versus about 1 in 12 (14.3% vs 8.6%) [6]. Two people taking ipamorelin died. Both had colon cancer surgery, and in both cases the surgical join in the bowel leaked afterward. Nobody on the placebo died. The FDA says it is unclear whether those deaths had anything to do with ipamorelin — but it pointed to them, along with the potassium and blood sugar differences, when it recommended in October 2024 against letting pharmacies compound ipamorelin [6].
Contraindications
- Active cancer or history of cancer
- Pregnancy or breastfeeding
- Pituitary disorders or tumors
- Known allergy to peptide components
- Children and adolescents (growth plates still open)
Which is right for you?
Choose GHRH (1-29) if...
- Children with growth hormone deficiency who need to catch up in height
- Adults seeking to optimize natural growth hormone levels
- People being tested for growth hormone deficiency
Choose Ipamorelin if...
- Muscle recovery and growth
- Anti-aging and vitality
- Body composition improvement
- Sleep quality enhancement