GHRH (1-29) vs Sermorelin
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].
The original growth hormone booster that works with your body's natural rhythm—it tells your pituitary gland to release more GH instead of replacing it, keeping your hormonal feedback system healthy and balanced.
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
Sermorelin
200–300 mcg
Frequency
GHRH (1-29)
Once daily at bedtime
Sermorelin
Once daily
Administration
GHRH (1-29)
Subcutaneous injection
Sermorelin
Subcutaneous injection
Cycle length
GHRH (1-29)
Continuous — the label treats until the growth plates fuse
Sermorelin
12+ weeks
Onset speed
GHRH (1-29)
Height velocity measurable at 6 months in children; nothing established in adults
Sermorelin
Moderate (1-2 weeks)
Evidence level
GHRH (1-29)
Human trials in children; one 19-person adult trial of a modified analogue
Sermorelin
Moderate human trials (Phase 1-2)
Benefit ratings
Growth and Development
Body Composition
Performance and Recovery
GH Optimization
Sleep Quality
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
Sermorelin
Molecular formula
C149H246N44O42S
Molecular weight
3357.9 g/mol
Half-life
10-20 minutes
Bioavailability
High when injected subcutaneously; degraded orally
CAS number
86168-78-7
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.
Sermorelin
Subcutaneous
100-200 mcg
Once daily at bedtime · 4-6 weeks
Lower nightly dose used in practice; GHRH(1-29) nightly injections raised GH/IGF-1 in older adults [2][3].
200-300 mcg
Once daily at bedtime · 3-6 months
Common adult maintenance dose; twice-daily GHRH(1-29) reversed age-related GH/IGF-1 decline in men [1][2].
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.
Sermorelin
Adults Experiencing Age-Related GH Decline
After age 30, your growth hormone production naturally declines about 14% per decade. [9] Sermorelin helps restore more youthful GH levels by stimulating your own pituitary rather than shutting it down with external hormones. [1][13] It's like giving your hormone system a gentle nudge back to where it used to be.
Body Composition Optimizers
If you're struggling to lose stubborn belly fat or build lean muscle despite diet and exercise, sermorelin can help shift your body composition over time. Studies show it increases lean mass and reduces fat, [2][8] especially in older adults whose natural GH has declined.
Sleep Quality Seekers
Growth hormone is intimately tied to deep, restorative sleep. [10] By enhancing your natural nighttime GH pulses, sermorelin often improves sleep quality as a welcome side effect. [8] Many users report falling asleep faster and waking more refreshed.
Those Wanting a Safer Alternative to HGH
Direct HGH injections bypass your body's feedback system and can suppress your own production. [13] Sermorelin works differently—it asks your pituitary to make more GH naturally. This preserves your body's regulatory mechanisms and carries a lower risk of side effects. [8]
Side effects
GHRH (1-29)
Common
- Transient facial flushing
- Injection site reaction
Uncommon
- Hypothyroidism
- Anti-GRF antibodies
- Transient raised blood lipids
Serious
- Hypersensitivity reaction
Sermorelin
Common
- Injection site reactions
- Facial flushing
- Headache
- Sleepiness or drowsiness
Uncommon
- Nausea
- Hyperactivity or difficulty sleeping
Serious
- Severe 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
Sermorelin
Evidence level
Moderate human trials (Phase 1-2)
FDA status
FDA approved for other use
Safety overview
Sermorelin has an excellent safety profile backed by FDA approval history and decades of clinical use. Unlike direct HGH, it works through your body's natural feedback mechanisms, which inherently limits excessive hormone levels. [8][13] Side effects are generally mild and transient—mostly injection site reactions and occasional flushing. [6] The peptide was FDA-approved in 1997 for pediatric use [7] and is one of the most well-studied growth hormone secretagogues available.
Contraindications
- Active cancer or history of cancer
- Pregnancy or breastfeeding
- Known allergy to sermorelin or any peptide components
- Pituitary tumors or other pituitary disorders
- Diabetic retinopathy
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 Sermorelin if...
- Anti-aging and vitality
- Body composition improvement
- Sleep quality enhancement
- Exercise recovery