Growth hormone vs GH secretagogues
Giving the hormone itself, or asking the pituitary to make more of its own.
Checked 2026-10-22 Researched and written by Kymata Health Editorial · Sources cited inline Report an error
Short answer
Injected growth hormone (somatropin and its weekly forms) acts on the GH receptor directly and bypasses the pituitary. Secretagogues, such as tesamorelin or ipamorelin, make the pituitary release more of its own GH, so release stays pulsed and still answers to the body's brakes. Only somatropin, the weekly GHs and tesamorelin carry US labels.
Do secretagogues keep the natural GH pulses?
In the studies that measured it, yes. Tesamorelin made overnight GH pulses larger without changing their number, and GH returned to baseline two weeks after stopping (Stanley 2011, JCEM). CJC-1295 with DAC raised trough GH 7.5-fold while pulse frequency and size were unchanged (Ionescu 2006, JCEM). Daily oral MK-677 raised 24-hour GH with pulse number unchanged (Chapman 1996, JCEM).
Do they still respond to the body's brakes?
Largely. GHRH analogs act through the pituitary, which still answers to somatostatin; a somatostatin analog cut the GH response to GHRH by 38% (Dimaraki 2003, Am J Physiol). They also depend on a working pituitary: the tesamorelin labels exclude people whose hypothalamic-pituitary axis has been disrupted (Egrifta WR label).
How do the evidence and labels compare?
Somatropin has US labels for GH deficiency in children and adults and several growth disorders (Genotropin label); three weekly forms followed (Sogroya label; Ngenla label; Skytrofa label). Among secretagogues, only tesamorelin has a current US label, for excess abdominal fat in adults with HIV (Egrifta WR label). Ipamorelin, GHRP-2, GHRP-6, hexarelin and CJC-1295 have small human studies; MK-677 has a two-year trial in older adults (Nass 2008, Ann Intern Med).
What is monitored on each?
IGF-1 and glucose on both. On somatropin, the labels lower the dose for side effects or IGF-1 above the age- and sex-specific range (Norditropin label), and list class warnings such as intracranial hypertension and fluid retention (Genotropin label). On tesamorelin, the label says to consider stopping when IGF-1 stays above 3 SDS, and HbA1c reached 6.5% or more in 5% vs 1% on placebo (Egrifta WR label).
Frequently asked questions
Questions
- Is a secretagogue a substitute for GH in GH deficiency?
- Not when the pituitary cannot make GH: secretagogues need a working pituitary to act on. Diagnosis and treatment are a specialist's decision.
- Which is allowed in sport?
- Neither. WADA prohibits GH, its weekly forms and the secretagogues at all times (S2).
Not medical advice This page summarises published labels and studies. It is not a recommendation to use any product; a clinician decides.