IGF-1 (Native).

Quick Overview.

Native IGF-1 (Insulin-like Growth Factor-1) is the exact, unmodified, 70-amino acid hormone that your body naturally produces in the liver in response to Growth Hormone (GH). In the medical world, it is manufactured as a recombinant human protein (rhIGF-1) and sold under the brand name Increlex (Mecasermin). Unlike the popular biohacker variants (LR3 and DES), native IGF-1 has no chemical modifications to extend its life or increase its potency. It is the pure, pharmaceutical-grade hormone.[1]

Growth Hormone (GH) is like the boss of a construction site. It doesn't actually do the building; it tells the workers what to do. IGF-1 is the actual worker that builds the muscle, bone, and tissue. Some children have a genetic defect where their body makes the boss (GH), but the boss can't talk to the workers (IGF-1). Increlex is simply injecting the workers directly into the body so the building can happen. Bodybuilders use it to flood their system with extra "workers" to build muscle faster than naturally possible.[2]

• Primary Use Case: Treating severe growth failure in children, extreme muscle recovery.
• Mechanism: Binds to the Type 1 IGF receptor (IGF-1R) to stimulate cell proliferation and inhibit apoptosis. It is identical to endogenous human IGF-1.[1][3]
• Who it is for: Pediatric patients with severe primary IGF-1 deficiency (Laron syndrome). Elite bodybuilders with massive budgets.
• Who it is NOT for: Beginners, anyone on a budget, or those who cannot manage the risk of severe hypoglycemia.

The Protocol & Usage Guide.

confidence_tier: well-established

Native IGF-1 is incredibly dangerous if misused. Because it is so structurally similar to insulin, it pulls sugar out of your blood and into your muscles at an alarming rate. The FDA black-box warning for Increlex is severe hypoglycemia. You must eat a carbohydrate-rich meal within 20 minutes before or immediately after injecting this hormone.

Standard Dosing (Medical)

Standard Dosing (Bodybuilding)

Note: Bodybuilders often use lower doses than the pediatric maximums because they are combining it with other anabolic agents.

Injection Site Guide

• Where to Inject: Subcutaneous (under the skin) into the abdomen, thigh, or buttocks. Rotate injection sites daily to prevent lipohypertrophy (localized fat growth).

Cycle Length

• Cycle Length: 4 to 6 weeks maximum for performance enhancement.
• Time Off: Take at least 4-6 weeks off to allow receptors to reset.

Nutritional Support & Recommended Supplements.

confidence_tier: well-established

Safety, Interactions & Side Effect Management.

confidence_tier: well-established

The FDA black-box warning for Increlex is severe hypoglycemia.

Side Effect Profile

Contraindications

• Absolute: Individuals with active cancer or a family history of aggressive cancers.
• Absolute: Individuals with closed epiphyses (growth plates) seeking height increases.
• Absolute: Individuals with a history of severe hypoglycemia or unstable diabetes.

Drug Interactions

• Insulin (Exogenous): SEVERE. Combining rhIGF-1 with exogenous insulin can cause a fatal drop in blood sugar.
• Corticosteroids: Moderate. High doses of corticosteroids can blunt the growth-promoting effects of IGF-1.

Common Stacks & Combinations.

confidence_tier: community

Body Composition & Training Guide.

confidence_tier: community

• Nutrient Partitioning: Because IGF-1 forces nutrients into muscle cells rather than fat cells, users can often eat in a massive caloric surplus (to build muscle) without gaining significant body fat.
• Tracking Progress: Track fasting blood glucose daily to ensure insulin sensitivity remains healthy.

Storage, Handling & Accessibility.

confidence_tier: well-established

• Storage (Increlex): Must be stored in the refrigerator (2°C to 8°C). Do not freeze. Protect from light. Once opened, the vial must be used within 30 days.
• WADA Status: Banned in competitive sports under section S2 (Peptide Hormones).
• Cost & Accessibility: Increlex is an orphan drug. Without insurance, a single 40mg vial can cost upwards of $8,000 to $12,000. "Native IGF-1" sold by research chemical sites is almost always fake, under-dosed, or actually just LR3, because manufacturing pure rhIGF-1 is incredibly difficult and expensive.

Bloodwork Monitoring Guide.

confidence_tier: well-established

Before starting and regularly during use:

• Fasting Glucose & HbA1c: Mandatory. You must monitor your blood sugar to ensure you are not developing insulin resistance or experiencing chronic hypoglycemia.
• IGF-1 Levels: Will be massively elevated during use.

Comparison to Similar Compounds.

confidence_tier: well-established

Deep Dive (For Advanced Researchers).

confidence_tier: well-established

Mechanism of Action

Mecasermin (Increlex) is a recombinant DNA-derived human insulin-like growth factor-1 (rhIGF-1). It contains 70 amino acids in a single chain with three intramolecular disulfide bridges, identical to the endogenous human IGF-1 sequence.[1]

In the human body, 99% of IGF-1 is bound to IGF-binding proteins (primarily IGFBP-3) and the Acid-Labile Subunit (ALS). This ternary complex extends the half-life of native IGF-1 to roughly 15-20 hours. However, when exogenous rhIGF-1 is injected, it must find available binding proteins. The functional half-life of an Increlex injection is approximately 5.8 hours.[4]

Cellular Pathways

1. Receptor Activation: Mecasermin binds to the Type 1 IGF receptor (IGF-1R), which is homologous to the insulin receptor.[3]
2. Metabolic Actions (Insulin-like): Because it can bind to both the IGF-1 receptor and the insulin receptor (though with lower affinity), it exerts potent hypoglycemic effects. It suppresses hepatic glucose production and stimulates peripheral glucose utilization.[5]
3. Mitogenic Actions (Growth): It activates the PI3K/Akt and MAPK pathways, stimulating DNA synthesis, cell proliferation, and inhibiting apoptosis. In children with open epiphyses, it stimulates linear bone growth at the epiphyseal plates. In adults, it stimulates muscle hypertrophy and hyperplasia.[6]

Clinical Trial Summary

• Primary IGFD: Increlex was approved based on clinical trials involving children with severe primary IGF-1 deficiency (Laron syndrome). These children have normal or high GH levels but a genetic mutation in the GH receptor, meaning their liver cannot produce IGF-1.[2]
• Results: In a pivotal trial, children treated with mecasermin grew an average of 8.0 cm in the first year, compared to a pre-treatment growth rate of 2.8 cm/year.[7]
• The Iplex Failure: A competing drug, Iplex (mecasermin rinfabate), combined rhIGF-1 with rhIGFBP-3 to extend the half-life and reduce hypoglycemia. However, due to patent disputes with Insmed and Genentech, Iplex was pulled from the market, leaving Increlex as the sole FDA-approved rhIGF-1 therapy.

Synergy & Antagonism Analysis

• The Binding Protein Bottleneck: Because native IGF-1 relies on IGFBP-3 to remain stable in the blood, injecting massive doses of Increlex can saturate the available binding proteins. The excess "free" IGF-1 is rapidly cleared by the kidneys and causes acute, severe hypoglycemia. This is why the LR3 and DES variants were created by biohackers—to evade the binding proteins entirely.[8]

Frequently Asked Questions (FAQ).

confidence_tier: community

Q: Can I buy real Increlex from a peptide website? A: Almost certainly not. Real Increlex is a tightly controlled, incredibly expensive pharmaceutical liquid. If a website is selling "Native IGF-1" as a $40 lyophilized powder, it is likely fake, or it is actually LR3.

Q: Why do bodybuilders use LR3 instead of Native IGF-1? A: Three reasons: 1) Cost. LR3 is cheap; Increlex is thousands of dollars. 2) Half-life. LR3 lasts 24 hours; Native lasts 6 hours. 3) Potency. LR3 doesn't bind to binding proteins, making it functionally stronger milligram-for-milligram.

Q: If I take this, will I grow taller? A: Only if your growth plates (epiphyses) are still open (usually closes between ages 16-21). If you are an adult, it will not make you taller; it will only make your muscles, organs, and bones thicker (acromegaly).

Q: How fast does the blood sugar drop happen? A: Very fast. The Tmax (time to maximum concentration in the blood) is roughly 2 hours, but the hypoglycemic effects can begin within 30 minutes of injection. You must eat immediately.

International Regulatory Status.

confidence_tier: well-established

Decision Tree.

confidence_tier: community

[Goal: Extreme Muscle Growth?]
  |
  +-- Can you afford $8,000+ per month for real Increlex?
        |
        +-- (No) -> STOP: Use IGF-1 LR3 or DES instead.
        |
        +-- (Yes) -> Do you have fast-acting carbs ready?
              |
              +-- (No) -> STOP: High risk of severe hypoglycemia.
              |
              +-- (Yes) -> Inject 40-50mcg subcutaneously.
                           Consume 30-50g carbs immediately.

Schema.org Data.

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  "@context": "https://schema.org",
  "@type": "MedicalEntity",
  "name": "Mecasermin",
  "alternateName": ["Increlex", "rhIGF-1", "Native IGF-1"],
  "description": "A recombinant human insulin-like growth factor-1 (rhIGF-1) used to treat severe primary IGF-1 deficiency, and used off-label for extreme muscle recovery.",
  "legalStatus": {
    "@type": "DrugLegalStatus",
    "description": "FDA-approved prescription drug. Prohibited in-competition by WADA."
  }
}

What we cited.