Peptides vs. Prohormones: What You Need to Know

If you have spent any time reading about performance enhancement, you have encountered both peptides and prohormones. In the early 2000s, prohormones were the supplement industry's biggest category -- legal steroid precursors sold alongside protein powder at retail stores. That era ended in 2014, but the compounds did not vanish from the conversation.

Peptides, meanwhile, have moved in the opposite direction. From niche research chemicals, they have grown into a multi-billion-dollar therapeutic category with FDA-approved drugs, large-scale clinical trials, and legitimate medical applications.

These two classes of compounds could not be more different in how they work, what they do to your body, and where they stand legally. Here is the full comparison.

Table of Contents

• What Are Prohormones?
• What Are Peptides?
• How Prohormones Work
• How Peptides Work
• Structural and Mechanistic Differences
• Muscle Growth and Performance
• Fat Loss
• Recovery and Healing
• Side Effects: Prohormones
• Side Effects: Peptides
• Liver Toxicity
• Hormonal Disruption
• Legal and Regulatory Status
• Head-to-Head Comparison
• What Is Available Today
• The Bottom Line
• References

What Are Prohormones?

Prohormones are inactive chemical precursors that the body converts into active hormones. In the bodybuilding context, the term almost always refers to compounds that the liver converts into active anabolic steroids -- primarily testosterone, nandrolone, or their derivatives.

The concept is straightforward: rather than taking testosterone directly (which has been a controlled substance since 1990), users take a precursor molecule that is one or two enzymatic steps away from becoming testosterone. The liver's cytochrome P450 enzymes and other metabolic machinery perform the conversion.

The first commercially significant prohormone was androstenedione ("andro"), which gained national attention when Mark McGwire acknowledged using it during his record-breaking 1998 baseball season. That publicity launched a prohormone supplement industry that would generate hundreds of millions of dollars in sales before regulators caught up.

Popular prohormones from the pre-ban era included:

• 1-Androstenedione (1-AD) -- Converted to 1-testosterone
• 4-Androstenediol -- Converted to testosterone
• Superdrol (methasterone) -- Technically a designer steroid marketed as a prohormone
• Epistane -- A methylated compound with direct androgenic activity
• Halodrol (chlorodehydromethylandrostenediol) -- A precursor to the oral steroid Turinabol

Many of these compounds were not true prohormones at all. They were active steroids marketed under the prohormone label to exploit a regulatory loophole.

What Are Peptides?

Peptides are short chains of amino acids (2-50 amino acids) that function as signaling molecules, hormones, or tissue-repair agents. They occur naturally in the body and can be synthesized for therapeutic use.

The peptide category relevant to this comparison includes:

• Growth hormone secretagogues -- CJC-1295, ipamorelin, GHRP-2, GHRP-6, and MK-677 (technically a non-peptide GH secretagogue) stimulate the pituitary gland to release more growth hormone.
• Healing peptides -- BPC-157 and TB-500 promote tissue repair, reduce inflammation, and accelerate recovery from injury.
• GLP-1 agonists -- Semaglutide and tirzepatide regulate appetite, blood sugar, and body weight.
• Other functional peptides -- PT-141 (sexual health), selank (anxiety), semax (cognitive function), and many others.

Unlike prohormones, peptides do not convert into steroid hormones. They signal the body to produce or regulate its own hormones through natural feedback mechanisms.

How Prohormones Work

Prohormones follow a two-step process:

Step 1: Oral administration and liver conversion. The prohormone is swallowed, absorbed through the gastrointestinal tract, and delivered to the liver via the portal vein. Liver enzymes (primarily 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase) convert the inactive precursor into an active androgen.

Step 2: Androgen receptor activation. The active hormone enters the bloodstream and binds to androgen receptors throughout the body -- in muscle, bone, skin, prostate, brain, and other tissues. This triggers increased protein synthesis, nitrogen retention, and muscle growth through the same pathways that testosterone uses.

The conversion is not efficient. Only a fraction of the oral dose survives liver metabolism to become the active hormone. To compensate, many prohormones were 17-alpha methylated -- a chemical modification that resists liver breakdown but dramatically increases hepatotoxicity.

The methylation modification is the same one used in oral anabolic steroids like Dianabol and Anadrol. The liver toxicity profile of methylated prohormones is comparable to that of these prescription steroids.

How Peptides Work

Peptides operate through entirely different biology:

Growth hormone secretagogues bind to receptors on pituitary somatotroph cells. CJC-1295 binds to the GHRH receptor, mimicking the natural growth hormone-releasing hormone signal. Ipamorelin binds to the ghrelin receptor (GHS-R), acting as a synthetic ghrelin analog. Both trigger GH release through the same pathways your body uses during deep sleep and exercise. The hypothalamic-pituitary axis remains intact -- natural feedback loops still regulate overall GH output.

Healing peptides like BPC-157 work through angiogenic (blood vessel forming), anti-inflammatory, and cytoprotective pathways. BPC-157 activates the VEGFR2-Akt-eNOS signaling cascade for blood vessel formation, stimulates the FAK-paxillin pathway for cell migration, and upregulates growth hormone receptor expression in fibroblasts. None of this involves androgen receptor signaling.

GLP-1 peptides bind to GLP-1 receptors on pancreatic beta cells and hypothalamic neurons, improving insulin sensitivity and reducing appetite. The mechanism has nothing to do with androgens, steroids, or muscle-building pathways.

The fundamental difference: prohormones add external hormones to your system (after conversion). Peptides ask your system to produce more of its own hormones or to activate non-hormonal repair pathways.

Structural and Mechanistic Differences

Feature	Prohormones	Peptides
Chemical structure	Cholesterol-derived steroid backbone	Amino acid chains
Mechanism	Converted to active steroids by liver enzymes	Bind specific receptors to trigger signaling cascades
Primary target	Androgen receptors (throughout the body)	Various receptors (GHRH-R, GHS-R, GLP-1R, VEGFR2)
Route of action	Hormone replacement/addition	Hormone stimulation or non-hormonal signaling
Feedback loop impact	Suppresses natural hormone production	Preserves natural feedback loops
Duration of action	Hours to days per dose	Varies (hours to weeks depending on the peptide)
Administration	Oral (capsules, tablets)	Mostly injectable; some oral (semaglutide)
Required liver processing	Yes (liver converts precursor to active form)	No (peptides are already active)

Muscle Growth and Performance

Prohormones: Significant but Temporary

Prohormones produce meaningful muscle gains. A study investigating 330 mg/day of the prohormone 3-beta-hydroxy-5-alpha-androst-1-en-17-one in 17 resistance-trained men found increases in both lean mass and strength over the study period. Anecdotal reports from the pre-ban era describe gains of 5-15 pounds of lean mass during 4-6 week prohormone cycles.

But these gains come with an asterisk. Because prohormones suppress natural testosterone production, much of the gained muscle is lost after the cycle ends unless the user runs post-cycle therapy (PCT) -- typically using compounds like clomiphene citrate or tamoxifen to restart the hypothalamic-pituitary-gonadal axis. Even with PCT, some users report losing 30-50% of cycle gains.

Peptides: Gradual and Sustainable

GH secretagogues like CJC-1295 and ipamorelin produce more modest but more sustainable body composition changes. Increased GH and IGF-1 levels support protein synthesis, improve nitrogen retention, and favor fat oxidation. Users typically report improved muscle recovery, better sleep, reduced body fat, and gradual lean mass gains over months of use.

The effects are less dramatic than prohormones, but they persist without the cycle-crash-PCT pattern. Because GH peptides do not suppress testosterone, there is no post-cycle loss to recover from.

BPC-157 does not build muscle directly, but it accelerates recovery from training-induced muscle damage. Faster recovery means higher training frequency and volume, which indirectly supports muscle growth over time.

Fat Loss

Prohormones can improve body composition by adding lean mass (which increases basal metabolic rate) and, in some cases, through mild androgenic effects on fat metabolism. But they are not fat loss tools. No clinical study has demonstrated significant fat reduction from prohormone use.

Peptides offer far stronger fat loss options:

• GLP-1 agonists: Semaglutide produced 14.9% body weight loss in the STEP 1 trial. Tirzepatide produced up to 22.5% in SURMOUNT-1. These are the most effective pharmaceutical fat loss interventions ever documented.
• GH secretagogues: Elevated growth hormone promotes lipolysis and shifts fuel utilization toward fat oxidation. Typical results are 2-5% body fat reduction over several months.
• Fragment 176-191: A modified fragment of the growth hormone molecule, specifically studied for its lipolytic (fat-burning) properties without the glucose-raising effects of full GH.

Recovery and Healing

This category is not even close. Peptides dominate.

BPC-157 has been studied in over 100 preclinical studies for tissue repair across tendons, ligaments, muscles, bones, GI tract, and neural tissue. It promotes angiogenesis, reduces inflammation, accelerates collagen deposition, and stimulates growth hormone receptor expression in fibroblasts.

TB-500 (thymosin beta-4) promotes wound healing, cardiac tissue repair, and reduction of scar tissue formation. It works by upregulating actin, a protein involved in cell migration and tissue remodeling.

Prohormones have zero documented healing properties. They build muscle through androgenic pathways, but they do not repair tendons, accelerate wound healing, or reduce inflammation. In fact, the rapid strength gains from prohormones can increase injury risk -- muscles grow stronger faster than tendons and ligaments can adapt, creating a strength-connective tissue imbalance.

Side Effects: Prohormones

The side effect profile of prohormones is extensive and well-documented:

Liver damage. Methylated prohormones (which includes most of the effective compounds from the pre-ban era) are hepatotoxic. The study on 3-beta-hydroxy-5-alpha-androst-1-en-17-one found a 113% increase in aspartate aminotransferase (AST), a direct marker of liver cell damage, along with a 5.1% decrease in serum albumin, indicating impaired liver function. 17-alpha methylated compounds are "as damaging to the liver as many toxic oral steroids."

Cardiovascular damage. The same study found a 32% elevation in LDL ("bad") cholesterol. Prohormones also reduce HDL cholesterol, creating a pro-atherogenic lipid profile. Long-term use is associated with high blood pressure and changes in the structure of the left ventricle of the heart.

Hormonal disruption. All effective prohormones suppress natural testosterone production. This causes testicular atrophy, decreased sperm count, reduced libido, erectile dysfunction, mood swings, and depression -- both during use and during the recovery period after cessation.

Estrogenic side effects. Some prohormones aromatize (convert to estrogen), causing gynecomastia (breast tissue development in males), water retention, and mood changes. Users often take aromatase inhibitors concurrently, adding another layer of side effects.

Other effects. Acne, hair loss (in genetically predisposed individuals), prostate enlargement, and behavioral changes including increased aggression have all been documented.

According to WebMD, prohormone side effects include "liver damage, infertility, behavioral changes, hair loss, and others." The National Institute on Drug Abuse states that anabolic steroids and their precursors "can cause severe, long-lasting, and in some cases, irreversible damage" including "early heart attacks, strokes, liver tumors, kidney failure, and psychiatric problems."

Side Effects: Peptides

The peptide side effect profile is substantially milder:

GH secretagogues (CJC-1295, ipamorelin, GHRP-2):

• Water retention (transient, typically resolves within weeks)
• Numbness or tingling in hands and feet
• Increased appetite (especially with ghrelin-mimetic peptides like GHRP-6)
• Injection site redness or irritation
• Headache (uncommon)

GLP-1 peptides (semaglutide, tirzepatide):

• Nausea (most common, affecting 20-44% of patients; usually transient)
• Vomiting, diarrhea, constipation
• Reduced appetite (intended effect, but can be excessive)
• Potential for gallbladder issues at higher doses

BPC-157:

• No serious adverse effects documented in animal studies, even at high doses
• No identified toxic or lethal thresholds
• No teratogenic, genotoxic, or anaphylactic effects observed
• Limited human safety data

No peptide in any of these categories has been associated with liver toxicity, testosterone suppression, cardiovascular lipid changes, or the endocrine disruption profile of prohormones.

Liver Toxicity

This comparison deserves its own section because liver damage is the most acute and dangerous risk associated with prohormones.

Methylated prohormones must survive first-pass hepatic metabolism. The 17-alpha methyl group that allows oral bioavailability is directly toxic to liver cells. This is the same chemical modification responsible for the liver toxicity of oral anabolic steroids like methandrostenolone (Dianabol) and oxymetholone (Anadrol).

Documented consequences of prohormone-induced liver injury include:

• Elevated AST and ALT (liver enzymes that spike when liver cells are damaged)
• Cholestasis (bile flow obstruction)
• Peliosis hepatis (blood-filled cysts in the liver)
• Hepatocellular carcinoma (liver cancer, in extreme cases)
• Acute liver failure (rare but documented)

Peptides bypass this problem entirely. Injectable peptides enter the bloodstream directly, avoiding first-pass liver metabolism. Even oral peptides like semaglutide use absorption-enhancing technology that does not involve methylation or hepatotoxic modifications. After decades of use and extensive clinical trial data, no therapeutic peptide has been associated with liver toxicity.

Hormonal Disruption

All prohormones that produce meaningful muscle-building effects suppress the hypothalamic-pituitary-gonadal (HPG) axis. When exogenous androgens (or their precursors) enter the bloodstream, the hypothalamus detects elevated hormone levels and reduces GnRH secretion. The pituitary responds by cutting LH and FSH production. The testes, deprived of their stimulating signals, reduce testosterone production and shrink.

This suppression is:

• Dose-dependent -- Higher prohormone doses cause greater suppression
• Duration-dependent -- Longer cycles cause more prolonged suppression
• Partially reversible -- Most users recover natural testosterone production within 1-6 months after cessation, with or without PCT, but some experience prolonged hypogonadism

GH-stimulating peptides do not interact with the HPG axis. They operate through the growth hormone axis (GHRH/GHS receptors on the pituitary), which is completely separate from the gonadal axis. Testosterone levels remain unchanged during peptide use. No PCT is needed.

Legal and Regulatory Status

Prohormones: Mostly Banned

The Designer Anabolic Steroid Control Act of 2014 (H.R. 4771), signed by President Barack Obama on December 18, 2014, reclassified most prohormones as Schedule III controlled substances. The Act expanded the list of regulated anabolic steroids to include roughly two dozen compounds and established penalties of up to $500,000 for false labeling.

The ban specifically targeted methylated prohormones like Superdrol, Epistane, Halodrol, and similar compounds that had been sold as "dietary supplements" to exploit a loophole in the original Anabolic Steroid Control Act of 1990.

Prohormones available after 2014 are DHEA-based compounds (dehydroepiandrosterone). These are weaker, legal, and go through a different two-step conversion process. They do not produce effects comparable to the pre-ban methylated prohormones.

Peptides: A Mixed Picture

Several peptides have full FDA approval:

• Semaglutide (Ozempic, Wegovy) for diabetes and obesity
• Tirzepatide (Mounjaro, Zepbound) for diabetes and obesity
• Tesamorelin (Egrifta) for HIV-associated lipodystrophy
• Liraglutide (Victoza, Saxenda) for diabetes and weight management

Many other peptides (BPC-157, CJC-1295, ipamorelin, TB-500) are not FDA-approved but are not scheduled as controlled substances. They exist in a regulatory gray zone -- legal to possess and sell as "research chemicals" but not approved for human therapeutic use.

The World Anti-Doping Agency (WADA) prohibits most performance-related peptides in competitive sports, including GH secretagogues and GH-releasing peptides.

Head-to-Head Comparison

Category	Prohormones	Peptides
Muscle building speed	Fast (weeks)	Slow (months)
Muscle building magnitude	Significant (5-15 lbs per cycle)	Moderate (gradual accumulation)
Fat loss	Indirect only	Strong (GLP-1 agonists)
Tissue healing	None	Strong (BPC-157, TB-500)
Liver toxicity	High (methylated compounds)	None documented
Testosterone suppression	Yes (all effective compounds)	No (GH peptides)
Post-cycle therapy required	Yes	No
Cardiovascular risk	High (lipid changes, BP elevation)	Low to beneficial
Legal status (US)	Mostly Schedule III controlled substances	Varies; some FDA-approved, some research-only
FDA-approved examples	None	Multiple (semaglutide, tirzepatide, etc.)
Administration	Oral	Mostly injectable
Duration of results	Temporary without PCT	Sustainable
Long-term safety data	Mostly negative	Positive for FDA-approved; limited for research peptides

What Is Available Today

Post-2014 Prohormones

The "prohormones" sold legally today are DHEA derivatives -- compounds like 1-DHEA (1-androsterone), 4-DHEA, and epiandosterone. These convert to active hormones through a two-step enzymatic process and produce effects that are dramatically weaker than the pre-ban methylated compounds.

These modern DHEA-based products are legal, less toxic, and far less effective. They occupy an awkward middle ground -- too weak for the results that attracted users to prohormones in the first place, but still carrying mild hormonal disruption risks.

Available Peptides

The peptide category continues to grow. FDA-approved peptides are available through prescription pharmacies. Research peptides (BPC-157, CJC-1295, ipamorelin, and others) are available through peptide synthesis companies, though quality varies significantly and consumers should demand third-party certificates of analysis.

A 2025 Stanford Medicine study demonstrated the continued innovation in peptide discovery. Researchers used artificial intelligence to identify a naturally occurring peptide (called BRP) that suppressed appetite and reduced body weight in animal models with fewer side effects than semaglutide -- specifically avoiding nausea, constipation, and significant muscle mass loss. While still in early research, this kind of targeted peptide development illustrates the direction the field is moving.

The Bottom Line

Prohormones and peptides represent two fundamentally different approaches to performance and health optimization. Prohormones are steroid precursors that directly alter hormone levels, producing fast but temporary muscle gains at significant cost to liver health, cardiovascular function, and endocrine balance. The most effective compounds were banned in 2014 for good reason -- they were functionally identical to oral anabolic steroids.

Peptides work with the body's existing biology. They signal, stimulate, and regulate rather than override. The effects are more gradual, but they come without the liver toxicity, testosterone suppression, and cardiovascular damage that define the prohormone experience. Several peptides have earned FDA approval through rigorous clinical trials -- a validation that no prohormone has ever achieved.

For anyone comparing these two categories in 2026, the choice is straightforward. Prohormones offer faster muscle gains with documented organ damage and legal restrictions. Peptides offer broader benefits -- healing, fat loss, hormone optimization, anti-aging -- with a dramatically better safety profile and legitimate medical backing.

Speed of results is not the only metric that matters. Sustainability, safety, and keeping your liver intact should be part of the equation.

References

1. U.S. Congress. "H.R. 4771 -- Designer Anabolic Steroid Control Act of 2014." Congress.gov

2. Granados, J., et al. "Prohormone supplementation during resistance training does not improve body composition or performance in young males." Journal of Sports Science and Medicine, 2014.

3. WebMD. "Prohormones: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews." WebMD

4. National Institute on Drug Abuse. "Anabolic Steroids and Other Appearance and Performance Enhancing Drugs." NIDA

5. Healthline. "Peptides for Bodybuilding: Efficacy, Safety, Types, and More." Healthline

6. Sikiric, P., et al. "Stable gastric pentadecapeptide BPC 157." Journal of Physiology-Paris, 2014.

7. Vasireddi, N., et al. "Emerging Use of BPC-157 in Orthopaedic Sports Medicine: A Systematic Review." Orthopaedic Journal of Sports Medicine, 2025. SAGE

8. Wilding, J.P.H., et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." New England Journal of Medicine, 2021.

9. Stanford Medicine. "Naturally occurring molecule rivals Ozempic in weight loss, sidesteps side effects." March 2025. Stanford Medicine

10. Zhi, X., et al. "Understanding peptide hormones: from precursor proteins to bioactive molecules." Trends in Biochemical Sciences, 2025. Cell