Growth Hormone, IGF-1 & Peptides: How the GH/IGF-1 Axis Works
A physician-guided explanation of growth hormone, IGF-1 and the peptides that influence this pathway—including sermorelin, tesamorelin, CJC-1295 and ipamorelin.
The GH/IGF-1 axis is the hormone-signaling system connecting the hypothalamus, pituitary gland, growth hormone and insulin-like growth factor-1. GHRH stimulates pituitary growth hormone release, somatostatin acts as a brake, and GH then drives direct metabolic effects while stimulating IGF-1 production in the liver and other tissues.
What Is the GH/IGF-1 Axis?
Growth hormone secretion is not constant. It occurs in pulses and is influenced by sleep, exercise, nutrition, glucose, body composition, age and other hormonal signals. GHRH stimulates GH release, while somatostatin suppresses it. Ghrelin and the growth hormone secretagogue receptor also participate in GH regulation.
Growth Hormone vs IGF-1: What’s the Difference?
| Feature | Growth Hormone (GH) | IGF-1 |
|---|---|---|
| Main source | Anterior pituitary | Primarily liver, with local production in other tissues |
| Secretion pattern | Highly pulsatile | More stable in circulation |
| Main role | Direct metabolic actions + stimulates IGF-1 | Mediates many downstream growth and tissue effects |
| Single blood test | Can be difficult to interpret because GH fluctuates | Often more useful as an integrated marker of GH activity |
This is why a random GH measurement is often less informative than patients expect. A single level may be low simply because the sample was drawn between normal GH pulses.
What Does Growth Hormone Actually Do?
GH has direct effects on fat metabolism and nutrient handling while also stimulating IGF-1 production. In true growth hormone deficiency, appropriate replacement can have clinically meaningful effects. That is different from trying to push GH above normal physiology for performance, fat loss or anti-aging.
Where Do Peptides Fit Into the GH/IGF-1 Axis?
| Therapy | Primary target | Key point |
|---|---|---|
| Sermorelin | GHRH receptor | Stimulates endogenous GH; historical FDA-approved product, none currently marketed |
| Tesamorelin | GHRH receptor | FDA approved for excess abdominal fat in adults with HIV and lipodystrophy |
| CJC-1295 | GHRH receptor pathway | Investigational; limited human clinical evidence and no FDA-approved indication |
| Ipamorelin | Growth hormone secretagogue receptor | Investigational; no FDA-approved indication |
| Recombinant HGH | GH receptor downstream | Provides exogenous GH directly rather than stimulating pituitary release |
FDA has highlighted limited clinical data and safety concerns around compounded CJC-1295 and ipamorelin. Their popularity online should not be confused with established clinical efficacy.
How Do Sermorelin and Tesamorelin Affect GH and IGF-1?
Learn how sermorelin acts through the GHRH receptor and what current evidence supports.
Explore tesamorelin’s FDA-approved indication, visceral-fat research and IGF-1 effects.
Compare mechanism, FDA status, visceral fat, weight loss, IGF-1 and safety.
Do GH and IGF-1 Help Build Muscle or Reduce Fat?
Growth hormone biology is real—but online discussions often jump from mechanism to outcome too quickly. Resistance training, adequate protein, calorie balance, sleep and treatment of metabolic disease remain foundational for body composition.
Tesamorelin is a useful example: it can significantly reduce visceral adipose tissue in adults with HIV-associated lipodystrophy, yet its FDA label specifically states that it is not indicated for weight-loss management.
Does Growth Hormone Decline With Age?
Aging, increased visceral adiposity, sleep changes and metabolic factors can all influence the somatotropic axis. The presence of lower GH signaling alone is not a diagnosis.
Is Higher IGF-1 Better?
The current tesamorelin prescribing information illustrates this clearly: FDA recommends monitoring IGF-1 because the effects of prolonged elevation are uncertain.
That is why “boosting IGF-1” should not be treated as an endpoint by itself.
How Do Doctors Evaluate the GH/IGF-1 Axis?
Because GH secretion is pulsatile, diagnosing growth hormone deficiency is more complex than ordering a single GH test. Endocrinology guidelines often rely on IGF-1 plus appropriately selected stimulation testing when true deficiency is suspected.
For general wellness concerns, fatigue, poor recovery or body-composition changes may have many more common explanations that deserve evaluation first.
GH/IGF-1 Peptides in Dallas: What Patients Should Know
At Sanjiva Medical Spa in Dallas, peptide-related care begins with the patient rather than a peptide menu. The goal is to understand the clinical problem before deciding whether the GH/IGF-1 axis should be targeted at all.
Explore Sanjiva Medical Spa’s approach to medical evaluation, laboratory review, body composition and individualized treatment planning.
Frequently Asked Questions
What is the GH/IGF-1 axis?
The GH/IGF-1 axis is the endocrine system connecting hypothalamic signals, pituitary growth hormone secretion and downstream IGF-1 production. GHRH stimulates GH release, somatostatin suppresses it, and growth hormone then exerts direct effects while stimulating IGF-1 production.
Is IGF-1 the same as growth hormone?
No. Growth hormone is secreted primarily by the pituitary and fluctuates in pulses. IGF-1 is produced largely in response to growth hormone, circulates more steadily and mediates many downstream growth and tissue effects.
What peptides increase growth hormone?
Peptides that can stimulate growth hormone include GHRH analogs such as sermorelin and tesamorelin, as well as growth hormone secretagogues such as ipamorelin. These peptides differ substantially in clinical evidence, FDA status and safety information.
Does sermorelin increase IGF-1?
It can. Sermorelin stimulates endogenous growth hormone release through the GHRH receptor, and growth hormone can subsequently increase IGF-1 production. Individual responses vary.
Does tesamorelin increase IGF-1?
Yes. Tesamorelin stimulates endogenous growth hormone and commonly increases IGF-1. Its FDA prescribing information recommends monitoring IGF-1 because the effects of prolonged elevations are not fully known.
Does growth hormone build muscle?
Growth hormone and IGF-1 participate in protein and muscle physiology, but increasing growth hormone signaling does not automatically produce clinically meaningful muscle gain in healthy adults. Training, nutrition, sleep and overall metabolic health remain major determinants of muscle growth.
Does growth hormone reduce visceral fat?
Growth hormone signaling influences fat metabolism, but this does not mean all GH-related therapies are proven visceral-fat treatments. Tesamorelin has specific evidence for reducing visceral fat in adults with HIV-associated lipodystrophy, which should not be generalized to all patients.
Does growth hormone decrease with age?
Yes. Growth hormone secretion generally declines with age. This age-related decline is physiological and does not by itself establish growth hormone deficiency or a need for treatment.
Is higher IGF-1 better?
No. Higher IGF-1 is not automatically better. IGF-1 is biologically active, and treatment should aim for appropriate clinical physiology rather than maximizing a laboratory value.
Considering Peptide Therapy in Dallas?
Learn more about Sanjiva’s approach or schedule an evaluation.
Selected References
- Bioletto F, et al. Central and peripheral regulation of the GH/IGF-1 axis: GHRH and beyond. Rev Endocr Metab Disord. 2025.
- Chesnokova V, et al. Update on regulation of GHRH and its actions on GH secretion in health and disease. Rev Endocr Metab Disord. 2025.
- U.S. Food and Drug Administration. EGRIFTA WR™ (tesamorelin) Prescribing Information. 2025.
- U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks.
