Growth Hormone Secretagogues Explained

Growth hormone secretagogues (GHS) are compounds that stimulate the pituitary gland to release more growth hormone (GH). Unlike exogenous growth hormone (which introduces synthetic GH directly into the body), secretagogues work by amplifying the body's own GH production through natural signaling pathways.

This distinction matters because secretagogues generally maintain the body's pulsatile GH release pattern — growth hormone is naturally released in pulses, primarily during sleep — rather than creating a constant, non-physiological elevation. Proponents argue this makes secretagogues safer than direct GH administration, though this claim has not been definitively established in large clinical trials for most of these compounds.

GHS compounds work through two main pathways: GHRH receptor agonism (mimicking growth hormone-releasing hormone) and ghrelin receptor agonism (mimicking the hunger hormone ghrelin, which also triggers GH release). Some compounds target one pathway; others target both.

Sermorelin is a synthetic analog of natural GHRH (growth hormone-releasing hormone), containing the first 29 amino acids of the 44-amino-acid GHRH sequence. It is the most established GH secretagogue with previous FDA approval history.

Sermorelin was FDA-approved as Geref for the diagnosis and treatment of growth hormone deficiency in children. It was voluntarily withdrawn from the market in 2008 by its manufacturer (not for safety reasons but for business reasons), and its approval was formally withdrawn in 2016.

Despite the withdrawal, Sermorelin remains available through compounding pharmacies (it was not placed on the Category 2 list) and is commonly prescribed by anti-aging and hormone optimization clinics.

Human studies have demonstrated that Sermorelin increases GH secretion and IGF-1 levels. A study in elderly adults showed improvements in body composition and sleep quality over 16 weeks of treatment. However, large-scale RCTs for specific clinical outcomes are limited.

Tesamorelin is a synthetic GHRH analog that is currently FDA-approved as Egrifta for the treatment of excess abdominal fat (lipodystrophy) in HIV-positive patients on antiretroviral therapy.

Tesamorelin has the strongest clinical evidence of any GH secretagogue, with Phase 3 clinical trials demonstrating significant reduction in visceral adipose tissue in HIV-associated lipodystrophy. It is the only GH secretagogue with a current FDA-approved indication.

The compound specifically stimulates the pituitary to release GH without the side effects associated with direct GH administration. Clinical trials showed a mean reduction of approximately 15% in trunk fat with tesamorelin versus placebo.

FDA status: Approved (Egrifta) for HIV-associated lipodystrophy. Not approved for general anti-aging or body composition optimization, though it is sometimes prescribed off-label.

CJC-1295 (with or without DAC — Drug Affinity Complex) and Ipamorelin are among the most popular research peptides in the GH secretagogue category. They are frequently discussed together because they are commonly combined in clinical and research settings.

CJC-1295 is a synthetic GHRH analog with a half-life of approximately 6-8 days (with DAC modification), compared to natural GHRH's half-life of minutes. This long half-life allows for less frequent dosing. Limited human pharmacokinetic data exists showing that CJC-1295 with DAC increases GH and IGF-1 levels for an extended period.

Ipamorelin is a selective growth hormone secretagogue that acts through the ghrelin receptor (GHS-R). It is considered selective because it stimulates GH release without significantly affecting cortisol or prolactin levels, which is a notable advantage over earlier ghrelin mimetics.

Key limitation: Despite widespread clinical use by anti-aging practitioners, CJC-1295 and Ipamorelin lack large published human clinical trials. The evidence base consists primarily of pharmacokinetic studies, small open-label observations, and extensive animal data. Both compounds are on the FDA Category 2 list.

MK-677 is not a peptide — it is a non-peptide, orally active growth hormone secretagogue that mimics ghrelin signaling. It is included here because it is commonly discussed alongside peptide GH secretagogues and targets the same biological pathway.

MK-677 has more published human data than most research GH secretagogues. Multiple human studies have demonstrated sustained increases in GH and IGF-1 levels with oral MK-677 administration. A 2-year study in elderly adults (n=65) showed sustained elevation of GH and IGF-1 to levels characteristic of young adults, with improvements in body composition.

However, MK-677 also increases appetite (consistent with its ghrelin-mimetic mechanism), cortisol levels, and blood glucose in some studies. These side effects are relevant considerations, particularly for extended use.

FDA status: Not approved. MK-677 has been studied in clinical trials for several indications (muscle wasting, osteoporosis, growth hormone deficiency) but has not received FDA approval. It was not placed on the Category 2 compounding ban because it is a small molecule, not a peptide.