GH secretagogues — Ipamorelin, CJC-1295, Tesamorelin, GHRP-2, GHRP-6, and Sermorelin — are among the most popular peptide categories in athletics. They raise growth hormone and IGF-1 without exogenous GH, and they are frequently described as "safe with no blood work needed."
That description is almost right, but not entirely. While secretagogues do not stress your liver, kidneys, or cardiovascular system the way AAS or even GH can, there are subtle changes in your blood work that tell you two important things: whether your protocol is actually working, and whether it is still safe to continue.
IGF-1: The Primary Efficacy Marker
If you are using a GH secretagogue, the single most important blood marker is IGF-1. GH secretion is pulsatile and difficult to capture with a single blood draw — but IGF-1 reflects integrated GH output over the preceding days and is much more stable. It is your primary tool for answering the question everyone should ask: is this protocol actually doing anything?
IGF-1 (Insulin-Like Growth Factor 1)
Timing matters. Blood draw timing for IGF-1 is less strict than for GH itself (IGF-1 is stable throughout the day), but you should still draw at the same time of day and in the same fasted state for consistent comparisons. Draw at least 8-12 hours after your last secretagogue dose to capture the integrated effect rather than a post-dose spike.
Target ranges. A well-functioning secretagogue protocol typically raises IGF-1 by 20-50% from baseline, putting most users in the 250-400 ng/mL range depending on age. If your IGF-1 does not budge after 4 weeks, your dose is too low, your compound is under-dosed, or the secretagogue you are using does not work well for your physiology.
GH Secretagogue Comparison
Not all secretagogues are created equal. Some are more effective at raising IGF-1, some have longer duration, and some introduce additional considerations:
GH Secretagogues Compared
| Marker | Ipamorelin | CJC-1295 (with DAC) |
|---|---|---|
| Mechanism | GHRP agonist — pure GH pulse | GHRH analog — sustained GH release |
| Duration of Action | ~2 hours per dose | ~7-14 days per dose (with DAC) |
| IGF-1 Increase | Modest (20-40%), dose-dependent | Significant (40-80%), sustained |
| Prolactin Effect | Minimal | None (GHRH, not ghrelin receptor) |
GHRP-6 vs. Sermorelin
| Marker | GHRP-6 | Sermorelin |
|---|---|---|
| Mechanism | GHRP agonist — ghrelin receptor | GHRH analog — pituitary stimulation |
| IGF-1 Increase | Moderate (30-60%) | Modest (15-30%) |
| Prolactin Effect | Significant — ghrelin cross-talk raises prolactin | None — no prolactin elevation |
| Cortisol Effect | Mild ACTH stimulation possible | None |
| Appetite Effect | Strong hunger increase (ghrelin agonist) | None |
Prolactin
Cortisol: The Subtle Signal
Ghrelin receptor agonists (GHRP-2, GHRP-6) can stimulate ACTH release, which in turn raises cortisol. The effect is subtle in most users but measurable in some, particularly at higher doses or with longer protocols. Cortisol elevation is typically not clinically significant at moderate secretagogue doses, but if you are combining secretagogues with other stressors (heavy training, calorie restriction, sleep deprivation), the cumulative cortisol load can affect recovery, body composition, and immune function.
Morning cortisol is the easiest marker to track. If you notice changes in sleep quality, water retention, or recovery that coincide with your secretagogue use, cortisol is worth a look — though most users will never see a meaningful change in this marker.
Glucose Impact on Secretagogues
Secretagogues raise GH, and GH raises glucose. However, the effect is much smaller than with exogenous GH because the total GH output from secretagogues is typically lower. Most users will not see significant changes in fasting glucose or HbA1c from secretagogues alone.
The exception: long-term users (6+ months of continuous use), high-dose protocols (multiple daily doses of potent secretagogues like CJC-1295 with DAC + GHRP-6), and users with pre-existing insulin sensitivity concerns. For these groups, an annual HbA1c check is sensible (JCEM: Growth hormone releasing peptides).
CJC-1295 with DAC: A Special Case
Practical Monitoring Schedule
For most secretagogue users, the monitoring burden is low but not zero. Here is the minimal practical protocol:
- Baseline: IGF-1, prolactin, morning cortisol, fasting glucose, HbA1c
- Week 4: IGF-1 only — to confirm the protocol is working. Also check prolactin if using GHRP-6
- Week 12: Full repeat of baseline panel, especially IGF-1 and glucose markers
- Annually for long-term users: HbA1c, fasting glucose, and consider an OGTT if using potent secretagogues
Secretagogues do not affect liver enzymes (AST, ALT, GGT), kidney markers (creatinine, eGFR), or lipid panels (HDL, LDL, triglycerides) at moderate doses. If you see changes in these markers, the cause is likely something else in your stack — not the secretagogue.