A receptor agonist that lives on the pituitary is a secretagogue: it secretes something the gland already knows how to make. CJC-1295 (no DAC) is a GHRH-receptor agonist. Ipamorelin is a ghrelin-receptor agonist. Tesamorelin is a more stable GHRH analog with a clinical history in a specific lipodystrophy indication.
This is a different object from a GLP-1 agonist, which acts on incretin receptors in pancreas and brain, and different again from a fragment like AOD-9604, which is a piece of the hormone itself rather than a releasing signal.
Why half-life is a design choice
Physiology releases GH in pulses. A thirty-minute analog can be timed onto that rhythm. A drug-affinity-complex analog that lingers for days flattens the pulse. Neither is ‘better’ as chemistry; they answer different experimental questions.
When two secretagogues are studied together, the rationale is orthogonal receptors, not a folklore stack. Write down which receptor you think you are hitting.