What is the difference between CJC-1295 with and without DAC?

CJC-1295 with DAC carries an albumin-binding complex that extends half-life to roughly six to eight days. CJC-1295 without DAC is Modified GRF (1-29), a short-acting GHRH fragment with a half-life of minutes that preserves pulsatile secretion patterns.

Why are GHRH analogs and ghrelin mimetics combined in research?

They act at different receptors on the same cell — the GHRH receptor and GHS-R1a — so their effects in preclinical models are more than additive, which is the rationale behind combination preparations.

Which growth hormone secretagogue is most selective?

Ipamorelin is the most selective in published preclinical work, producing GH release with minimal effect on cortisol or prolactin, while GHRP-6 is the least selective and shows pronounced appetite signalling.

Compound classes · 8 min read

Growth hormone secretagogues: GHRH analogs versus ghrelin mimetics

Two distinct receptor systems are routinely grouped under one label. Understanding which is which explains the DAC question, the selectivity differences and the pulsatility literature.

Two receptors, not one

Compounds described as growth hormone secretagogues fall into two mechanistically unrelated groups. GHRH analogs — sermorelin, tesamorelin, CJC-1295 — act at the GHRH receptor on somatotrophs and amplify the amplitude of endogenous secretory pulses. Ghrelin mimetics — ipamorelin, GHRP-2, GHRP-6, hexarelin — act at the growth hormone secretagogue receptor GHS-R1a and both stimulate release and suppress somatostatin tone.

Because the two act at different receptors on the same cell, their effects in preclinical models are more than additive, which is the entire rationale for the combination preparations that pair a GHRH analog with a ghrelin mimetic.

The DAC question

CJC-1295 exists in two distinct forms and the distinction is the most frequently confused point in this class. CJC-1295 with DAC carries a Drug Affinity Complex — a maleimidopropionic acid group that forms a covalent bond with serum albumin, extending half-life from minutes to roughly six to eight days.

CJC-1295 without DAC is not a variant of that molecule; it is Modified GRF (1-29), a 29-residue GHRH fragment with four stabilising substitutions and a half-life measured in minutes. The literature on the two diverges accordingly: the DAC form produces a sustained elevation in circulating GH, while the no-DAC form preserves the pulsatile secretion pattern that much of the physiological literature treats as mechanistically significant.

Selectivity within the ghrelin mimetics

Ipamorelin is the most selective compound in the group, producing GH release in preclinical models with minimal effect on cortisol or prolactin. GHRP-6 is markedly less selective and is characterised in the literature by strong appetite signalling through central ghrelin receptor activation. GHRP-2 sits between the two. Hexarelin is the most potent per unit mass but shows the most pronounced receptor desensitisation on repeated exposure.

Selectivity is therefore the deciding variable in study design. A protocol interrogating GH axis behaviour specifically will confound itself with GHRP-6; one investigating appetite signalling may specifically require it.

Downstream markers

Growth hormone itself is pulsatile and a single timepoint measurement is close to uninterpretable. IGF-1, produced hepatically in response to GH and with a far longer half-life, is the conventional integrated readout for this class and is what most published work reports.

Note that IGF-1 LR3 — an analog with reduced binding-protein affinity and an extended half-life — is a downstream effector rather than a secretagogue, and belongs to a different part of the axis entirely despite being catalogued alongside these compounds.

Frequently asked questions

What is the difference between CJC-1295 with and without DAC?: CJC-1295 with DAC carries an albumin-binding complex that extends half-life to roughly six to eight days. CJC-1295 without DAC is Modified GRF (1-29), a short-acting GHRH fragment with a half-life of minutes that preserves pulsatile secretion patterns.
Why are GHRH analogs and ghrelin mimetics combined in research?: They act at different receptors on the same cell — the GHRH receptor and GHS-R1a — so their effects in preclinical models are more than additive, which is the rationale behind combination preparations.
Which growth hormone secretagogue is most selective?: Ipamorelin is the most selective in published preclinical work, producing GH release with minimal effect on cortisol or prolactin, while GHRP-6 is the least selective and shows pronounced appetite signalling.