What are growth hormone secretagogues?
Growth hormone secretagogues (GHSs) are compounds that stimulate the pituitary gland to produce and release growth hormone. Unlike exogenous GH injections, which suppress natural production, secretagogues work with the body's own signaling pathways and preserve the pulsatile pattern of GH release.
CJC-1295: a long-acting GHRH analog
CJC-1295 is a synthetic analog of growth hormone-releasing hormone (GHRH). Native GHRH has a half-life of only about 7 minutes due to rapid enzymatic degradation by DPP-IV. CJC-1295 was engineered to resist this degradation.
With DAC vs. without DAC
The original version includes a Drug Affinity Complex (DAC) that extends the half-life to approximately 6-8 days, producing sustained GH and IGF-1 elevation. A study by Teichman et al. (2006) found that a single injection increased mean GH levels 2- to 10-fold for 6 days and elevated IGF-1 by 1.5- to 3-fold for 9-11 days.
The version without DAC, often called Modified GRF (1-29), has a half-life of roughly 30 minutes. It produces acute GH pulses more similar to natural physiology and is frequently paired with ipamorelin.
Note: When researchers or clinics refer to "CJC-1295" in combination protocols, they typically mean the version without DAC (Modified GRF 1-29), not the long-acting DAC variant.
Ipamorelin: a selective ghrelin mimetic
Ipamorelin is a synthetic pentapeptide that activates the ghrelin receptor (GHS-R). Research by Raun et al. (1998) demonstrated that ipamorelin stimulates GH release in a dose-dependent manner without significantly affecting cortisol, prolactin, FSH, LH, or TSH. That selectivity distinguishes it from GHRP-6 and GHRP-2.
MK-677 (Ibutamoren): an oral non-peptide secretagogue
MK-677 is technically a non-peptide spiropiperidine compound that agonizes the ghrelin receptor. Its chemical structure allows it to survive gastrointestinal digestion, making it orally bioavailable. Murphy et al. (1998) showed that 25 mg/day for 12 months increased IGF-1 levels to those of healthy young adults in elderly subjects.
Because it broadly activates the ghrelin pathway, MK-677 tends to increase appetite and can affect fasting glucose and insulin sensitivity. Nass et al. (2008) reported that two months of treatment increased fasting glucose and impaired insulin sensitivity.
Head-to-head comparison
| Feature | CJC-1295 (no DAC) | Ipamorelin | MK-677 |
|---|---|---|---|
| Compound type | Synthetic GHRH analog (peptide) | Synthetic ghrelin mimetic (peptide) | Non-peptide GHS-R agonist |
| Mechanism | Activates GHRH receptor | Activates ghrelin receptor (GHS-R1a) | Activates ghrelin receptor (GHS-R1a) |
| Route | Subcutaneous injection | Subcutaneous injection | Oral |
| Half-life | ~30 minutes | ~2 hours | ~5 hours (effects last ~24 hours) |
| GH release pattern | Acute pulse, mimics natural signaling | Acute pulse, dose-dependent | Sustained elevation over 24 hours |
| Effect on cortisol | No significant increase | No significant increase | No significant increase |
| Appetite stimulation | Minimal | Minimal | Significant (ghrelin-mediated) |
| Insulin/glucose effects | Not significant | Not significant | May increase fasting glucose |
The synergistic stack: CJC-1295 + Ipamorelin
GHRH and ghrelin act on different receptors on the same pituitary cells, and their GH-releasing effects are synergistic rather than merely additive. Arvat et al. (2001) showed that co-administration produced GH responses substantially greater than the sum of each compound given alone.
This combination is favored because both compounds have relatively clean side-effect profiles. Neither significantly raises cortisol or prolactin, and neither drives the strong appetite stimulation associated with MK-677.
Research status
CJC-1295 with DAC was studied in Phase I/II clinical trials showing robust GH and IGF-1 increases, but clinical development was paused. Ipamorelin was evaluated in a Phase II trial for post-operative ileus recovery (Beck et al., 2008). MK-677 has the most extensive clinical trial history, studied for age-related GH decline, body composition, bone density, and sleep quality. Despite promising data, none have received regulatory approval.
Note: None of these three compounds are FDA-approved medications. All research discussed here comes from clinical trials, preclinical studies, and investigational use.
- CJC-1295 (without DAC) produces acute GH pulses mimicking natural physiology. Most effective combined with a ghrelin mimetic.
- Ipamorelin is the most selective ghrelin-receptor agonist studied, stimulating GH without raising cortisol, prolactin, or appetite.
- MK-677 is an oral non-peptide option with the most clinical data, but its broader ghrelin-pathway activation increases appetite and may affect glucose metabolism.
- The CJC-1295 + Ipamorelin combination exploits GHRH/ghrelin synergy while maintaining a clean side-effect profile.
Sources
- Teichman SL, et al. Prolonged stimulation of growth hormone and insulin-like growth factor I secretion by CJC-1295 in healthy adults. J Clin Endocrinol Metab. 2006;91(3):799-805.
- Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.
- Murphy MG, et al. Effect of alendronate and MK-677 on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. J Clin Endocrinol Metab. 2001;86(3):1116-1125.
- Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Ann Intern Med. 2008;149(9):601-611.
- Copinschi G, et al. Effects of a 7-day treatment with MK-677 on 24-hour GH profiles in normal young men. J Clin Endocrinol Metab. 1997;82(2):590-596.
- Arvat E, et al. Endocrine activities of ghrelin: comparison and interactions with hexarelin and GH-releasing hormone. J Clin Endocrinol Metab. 2001;86(3):1169-1174.
- Beck DE, et al. Ipamorelin for postoperative ileus: a Phase II clinical trial. J Gastrointest Surg. 2008;12(7):1261.