AOD-9604 While Breastfeeding: Is It Safe? What Women Need to Know

What Is AOD-9604 and Why Are Postpartum Women Asking About It?

AOD-9604 is a synthetic peptide derived from the C-terminal region of human growth hormone, specifically amino acids 176 to 191. Researchers originally studied it as an anti-obesity compound because it appeared to stimulate lipolysis and inhibit lipogenesis in preclinical models without producing the insulin-resistance effects seen with full-length growth hormone. The name stands for Anti-Obesity Drug 9604.

Many postpartum women encounter AOD-9604 through telehealth weight-loss clinics or compounding pharmacies. The draw is understandable. You have just been through pregnancy, your body composition has shifted, and you may feel pressure to lose weight quickly while also nursing an infant. Peptide-based "metabolic" protocols are marketed heavily in this space, and AOD-9604 is frequently included.

The problem is that the evidence base for AOD-9604 in humans is thin even outside of breastfeeding, and it is essentially nonexistent for lactating women. Atkins et al. (2016) conducted early phase I/II trials in non-pregnant adults showing that oral AOD-9604 at doses between 1 mg and 9 mg daily appeared well tolerated, but those trials enrolled no pregnant or lactating participants and were not designed to assess reproductive safety.

The Compounding Pharmacy Pathway

Because AOD-9604 is not FDA-approved, women who use it receive it through 503A compounding pharmacies, which prepare individualized prescriptions. The FDA's compounding framework does not require the same safety and efficacy studies that new drug applications demand. This means no manufacturer has ever submitted lactation data to the FDA, and no labeling exists to guide you or your clinician.

Why Postpartum Weight Loss Feels Urgent

Research published in Obstetrics and Gynecology shows that approximately 47% of women who gain within Institute of Medicine guidelines during pregnancy still retain more than 5 kg at six months postpartum. That retained weight is real, it affects self-image and long-term cardiometabolic risk, and the desire to address it is medically valid. Acknowledging that context matters when discussing why women seek out unproven interventions.

What the Science Actually Shows: Human Growth Hormone, Peptides, and Breast Milk

Understanding the gap in AOD-9604 data requires understanding what we do know about growth hormone biology during lactation.

Endogenous Growth Hormone During Breastfeeding

Prolactin, not growth hormone, is the dominant pituitary hormone of lactation. Still, growth hormone does play a supporting role in milk production, particularly in modulating maternal insulin-like growth factor 1 (IGF-1) levels. The National Library of Medicine's LactMed database is the primary U.S. Reference for drug safety in breastfeeding, and as of this article's review date it contains no entry specific to AOD-9604, reflecting the complete absence of published lactation data for this peptide.

What We Know About Peptide Transfer Into Breast Milk

Peptides vary widely in their ability to cross into breast milk and to survive the infant's gastrointestinal tract. Small peptides below about 1,000 daltons tend to transfer more readily. AOD-9604 has a molecular weight of approximately 1,815 daltons. At that size, passive diffusion into milk is less efficient, but active transport mechanisms exist for some peptides of similar size. The NLM Drugs and Lactation Database (LactMed) explains that even when a drug transfers into milk, oral bioavailability in the infant depends on gastric acid degradation, intestinal absorption, and first-pass metabolism. For peptides, gastric proteolysis often reduces systemic exposure. None of these steps have been studied for AOD-9604 specifically in a lactating dyad.

The Extrapolation Problem

Because no milk-transfer data exists, any reassurance a clinician offers about AOD-9604 during breastfeeding is extrapolated from:

• General peptide pharmacokinetics in non-lactating adults
• Structural analogy to growth hormone fragments
• The assumption that gastric degradation would limit infant exposure

Extrapolation is not the same as evidence. ACOG Committee Opinion 743 addresses pharmacokinetics in pregnancy and reinforces that maternal physiologic changes alter drug disposition in ways that cannot simply be assumed from non-pregnant adult data. The same principle applies to lactation: the lactating state changes maternal volume of distribution, renal clearance, and protein binding in ways that have not been characterized for AOD-9604.

A useful framework for evaluating any uncharacterized peptide during breastfeeding asks three questions: Is there milk-transfer data? Is there infant oral bioavailability data? Is there infant safety data from any exposure route? For AOD-9604, the answer to all three is no.

Pregnancy Safety: An Even Larger Evidence Gap

If you are postpartum but not yet done with your family, or if you are considering future pregnancies, the pregnancy data for AOD-9604 is equally absent.

FDA Pregnancy Category and Human Data

AOD-9604 predates the FDA's 2015 Pregnancy and Lactation Labeling Rule (PLLR), which replaced the old A/B/C/D/X letter categories with narrative summaries of human and animal data. Because AOD-9604 has never received FDA approval, it has no PLLR label at all. No pregnancy exposure registry exists. No case series in pregnant women has been published.

Animal Reproductive Toxicology

The original Australian phase II program by Metabolic Pharmaceuticals studied AOD-9604 in rodent and non-rodent species for general toxicology. Those studies were conducted in the early 2000s and focused on metabolic endpoints rather than reproductive outcomes. Specific embryo-fetal developmental toxicology studies in the standard ICH S5 format were not published in peer-reviewed literature accessible through PubMed. This is a significant gap. Standard drug development requires ICH S5(R3) reproductive toxicology studies before human use in reproductive-age women, and that package does not appear to exist for AOD-9604 in the public domain.

Growth Hormone Fragments and Fetal Development

Full-length growth hormone does not cross the placenta in significant amounts due to its large molecular size (22 kDa). AOD-9604 at 1.815 kDa is far smaller and theoretically more capable of placental transfer, though no direct measurement has been performed. The placenta expresses growth hormone receptors and produces its own placental growth hormone variant, meaning exogenous growth-hormone-related peptides could theoretically interact with placental function. This is speculative. Speculative risk is not the same as demonstrated harm, but when data are absent, the precautionary principle applies.

Life-Stage Considerations: From Trying to Conceive Through Weaning

Trying to Conceive

Women with PCOS frequently seek weight-loss support while trying to conceive, and AOD-9604 appears in some functional medicine protocols for this population. ACOG Practice Bulletin 194 recommends lifestyle modification as first-line treatment for weight management in PCOS, with metformin and letrozole as evidence-based pharmacologic options for metabolic and ovulatory dysfunction. AOD-9604 appears in none of the PCOS or fertility guidelines from ASRM because no reproductive safety data supports its use.

Pregnancy

Stop AOD-9604 before attempting conception. Given the complete absence of pregnancy safety data, continuing use through conception or into the first trimester carries undefined risk to an embryo during the period of organogenesis, which runs from approximately weeks 3 through 10 of gestation.

Postpartum and Lactation

This is where most women encounter the AOD-9604 question. The postpartum period brings real metabolic challenges: insulin sensitivity shifts, adipose redistribution, thyroid fluctuation (postpartum thyroiditis affects roughly 5 to 10% of women), and sleep deprivation that dysregulates appetite hormones. Weight loss during active lactation also requires care because caloric deficit can reduce milk supply, and some weight-loss interventions alter milk composition.

No study has examined AOD-9604's effect on milk volume or milk macronutrient composition.

After Weaning

Once breastfeeding is complete, the risk to the infant from milk transfer disappears. The question shifts to adult safety and efficacy. Even then, AOD-9604 has no approved indication. The most advanced clinical trial, a phase II trial by Metabolic Pharmaceuticals published in 2004, showed modest weight loss that did not reach statistical significance versus placebo at the primary endpoint. The drug never received approval anywhere in the world.

What Compounding Clinics Are Telling Women (and What They Are Leaving Out)

Many telehealth platforms and compounding pharmacy partners present AOD-9604 as "a fragment of your body's own growth hormone" to suggest inherent safety. That framing omits several important facts.

First, the fact that a molecule resembles an endogenous compound does not guarantee safety at exogenous doses and routes. Oxytocin is endogenous; synthetic IV oxytocin still carries maternal risks including uterine hyperstimulation and hyponatremia.

Second, subcutaneous injection bypasses the gastrointestinal degradation that might otherwise limit systemic exposure to a peptide. The injectable form delivers the peptide directly into the systemic circulation, from which it can distribute to the mammary gland.

Third, "research chemical" or "for research use only" labeling from some suppliers means the product has not been manufactured under the FDA's Current Good Manufacturing Practice (cGMP) regulations, raising additional concerns about purity, potency, and contamination that are especially relevant when an infant is exposed through breast milk.

Safer Alternatives for Postpartum Weight Management

The good news is that effective, evidence-backed options exist for postpartum women who want to improve body composition without turning to uncharacterized peptides.

Nutrition During Lactation

Lactating women need approximately 340 to 400 additional kilocalories per day above pre-pregnancy needs according to Dietary Guidelines for Americans 2020-2025. A modest caloric deficit of 500 kcal/day below total energy expenditure is generally compatible with maintained milk supply in well-nourished women, though individual responses vary. Working with a registered dietitian who specializes in perinatal nutrition is the most evidence-based first step.

Physical Activity

ACOG Committee Opinion 804 supports resuming aerobic and strength exercise postpartum as soon as it is medically safe, noting benefits for weight management, mood, and cardiovascular health. Resistance training specifically helps preserve lean mass during a caloric deficit.

FDA-Approved Pharmacologic Options After Weaning

Once breastfeeding ends, several FDA-approved medications may be appropriate depending on your BMI, comorbidities, and goals. GLP-1 receptor agonists such as semaglutide (Wegovy) are approved for chronic weight management in adults with a BMI of 30 or greater, or 27 with a weight-related comorbidity. Semaglutide is not recommended during breastfeeding due to insufficient data, but it becomes an option after weaning and represents a far more studied intervention than AOD-9604. A conversation with your clinician about timing and eligibility is the appropriate starting point.

Addressing Underlying Conditions

Postpartum thyroiditis, insulin resistance from PCOS, and elevated cortisol from sleep deprivation all contribute to difficulty losing weight after birth. Treating the underlying cause is more effective than adding an unproven peptide. A postpartum metabolic workup that includes TSH, fasting glucose, and insulin can identify actionable targets.

Who Should Absolutely Not Take AOD-9604

The following women should not use AOD-9604 regardless of breastfeeding status:

• Anyone currently pregnant or planning pregnancy within the next three months
• Anyone actively breastfeeding an infant
• Anyone with a personal or family history of growth-hormone-sensitive tumors, including certain pituitary adenomas
• Anyone with active malignancy, given that growth-hormone-related signaling pathways interact with IGF-1 and cell proliferation, though no specific oncologic safety data for AOD-9604 exists
• Anyone purchasing from unverified online suppliers selling "research-grade" peptides without pharmaceutical-grade manufacturing documentation

Talking to Your Provider

If a telehealth clinic is recommending AOD-9604 while you are breastfeeding, ask these specific questions:

1. What peer-reviewed lactation safety data are you relying on?
2. Has milk-transfer been measured for this peptide?
3. What is your liability if my infant is harmed?
4. Are you prescribing through an FDA-registered 503A compounding pharmacy?
5. What FDA-approved alternative have you considered for my goals?

A clinician who cannot answer question one directly, by citing a specific published source, is relying on opinion, not evidence. You deserve evidence.

A Note on the Evidence Gap for Women in Research

Women have been systematically excluded from early-phase pharmacology trials for decades. The NIH Revitalization Act of 1993 required inclusion of women in NIH-funded clinical research, but peptide compounds studied outside the NIH grant system, including many compounded peptides, face no such requirement. AOD-9604's clinical development was conducted primarily in Australia by a private company. Lactating and pregnant women were not enrolled in any phase of that development program. The evidence gap you are navigating is not an accident; it reflects a structural failure in how reproductive-age women have been treated as research subjects.

That failure places the burden on you to ask harder questions and on your clinician to be transparent about what is known versus assumed.