Compounds / HGH 191AA
HGH 191AA
Also known as: Somatropin; recombinant human growth hormone (rhGH); somatropin (191 residues); hGH
Primary research focus: Growth hormone replacement and growth disorders (and specific wasting and metabolic indications)
Last updated July 2026 · Reviewed against FDA labeling and published research.
What is HGH 191AA?
HGH 191AA is recombinant human growth hormone (somatropin), a 191-amino-acid single-chain protein identical to the growth hormone made by the pituitary gland. The '191AA' label distinguishes it from an older 192-amino-acid version (somatrem). It is FDA-approved and marketed under many brand names for growth hormone deficiency and several other approved conditions. It is a prescription biologic, not a research chemical.
Somatropin binds the growth hormone receptor on target tissues, triggering JAK2/STAT signaling and stimulating hepatic and local production of insulin-like growth factor 1 (IGF-1), which mediates most of its growth-promoting effects. It promotes longitudinal bone growth (before growth-plate closure), increases lean body mass and protein synthesis, promotes lipolysis, and has counter-regulatory (anti-insulin) metabolic effects that can raise blood glucose. Long-acting formulations (for example, pegylated or albumin-binding versions) extend the dosing interval.
How it’s supplied
Brand / trade names: Genotropin, Humatrope, Norditropin, Omnitrope, Saizen, Serostim, Zorbtive
Supplied as FDA-approved prescription products, typically as lyophilized powder with diluent or as prefilled pens and cartridges for subcutaneous injection. Brands include Genotropin, Humatrope, Norditropin, Omnitrope, Saizen, Zomacton, and Nutropin (for growth-related indications), Serostim (HIV-associated wasting), and Zorbtive (short bowel syndrome). Long-acting somatropin products (for example, lonapegsomatropin, somapacitan, somatrogon) are also approved.
Dosage Chart
Units shown are for a U-100 insulin syringe (100 units = 1 mL), calculated from the vial size and BAC water you select. Always confirm against your prescription and your syringe markings.
| Phase | Dose | Frequency | Notes |
|---|---|---|---|
| Weeks 1-8 | 1IU | 1x Daily | — |
| Weeks 9-16 | 2IU | 1x Daily | — |
- Rotate injection sites to reduce irritation and lipohypertrophy
- Not for use during pregnancy or breastfeeding
- Do not exceed the recommended dose to try to speed results
- Typically administered on an empty stomach at bedtime to align with natural nocturnal GH releases
Potential Benefits and Side Effects
Effects reported in published research. Not a promise of results, and not medical advice.
- Established, FDA-approved therapeutic effects (indication-specific).
- Restores growth in children with growth hormone deficiency and other approved short-stature conditions.
- Improves body composition, bone density, and metabolic parameters in adult growth hormone deficiency.
- Increases lean body mass and reduces wasting in HIV-associated wasting (Serostim).
- Improves fluid and nutrient absorption in short bowel syndrome (Zorbtive).
- Fluid retention: edema, joint pain, muscle pain, and carpal tunnel symptoms.
- Glucose intolerance or new or worsened diabetes.
- Injection-site reactions and, rarely, lipoatrophy.
- Intracranial hypertension (headache, visual changes) and, in children, slipped capital femoral epiphysis or scoliosis progression.
- Hypothyroidism and, rarely, pancreatitis; monitoring is required.
Warnings and contraindications
Important safety information. This is not exhaustive — read the full prescribing information and consult your prescriber or pharmacist.
- Based on the FDA-approved labeling; the following are important, not exhaustive.
- Contraindicated and dangerous in acute critical illness (increased mortality was seen in critically ill adults).
- In Prader-Willi syndrome, deaths have occurred in patients with severe obesity, a history of airway obstruction, sleep apnea, or respiratory impairment.
- Growth hormone can cause or worsen glucose intolerance and diabetes, fluid retention (edema, arthralgia, carpal tunnel), intracranial hypertension, and slipped capital femoral epiphysis or scoliosis progression in children.
- It is contraindicated with active malignancy and requires caution given theoretical effects on tumor growth; monitor for new or recurrent neoplasia.
- It is prohibited in sport under the WADA Prohibited List.
- Some diluents contain benzyl alcohol, which is not for use in newborns.
- Per the approved labeling: acute critical illness (recent open-heart or abdominal surgery, multiple trauma, acute respiratory failure); active malignancy; Prader-Willi syndrome with severe obesity or severe respiratory impairment; active proliferative or severe non-proliferative diabetic retinopathy; closed epiphyses when used for height increase; and known hypersensitivity.
Reconstitution Steps
How to prepare the lyophilized vial. Confirm specifics with your pharmacist or prescriber.
- Use the specific diluent supplied with the product; the steps below describe reconstituting a lyophilized somatropin vial or cartridge.
- Confirm the product, strength, and the supplied diluent before starting.
- Wash your hands and gather supplies: the somatropin vial or cartridge, the supplied diluent, an alcohol swab, and the appropriate device or sterile syringe.
- Let the components reach room temperature if refrigerated.
- Wipe the stopper of the powder and the diluent with a fresh alcohol swab and let them dry.
- Add the supplied diluent slowly down the inside wall of the powder vial (or follow the pen or cartridge instructions).
- Do not shake. Gently swirl or roll until fully dissolved.
- Inspect the solution: it should be clear and colorless with no particles. Do not use if cloudy or discolored.
- Note the resulting concentration for reference, then refrigerate and use within the product-specific in-use window.
US regulatory status
Classifications are public record but can change. For reference only, not legal advice.
Development: Recombinant somatropin has been FDA-approved since the 1980s and is used across many indications: pediatric and adult growth hormone deficiency, Turner syndrome, Prader-Willi syndrome, small for gestational age with failure to catch up, Noonan syndrome, SHOX deficiency, chronic renal insufficiency (pediatric), and idiopathic short stature, plus HIV-associated wasting (Serostim) and short bowel syndrome (Zorbtive). Newer long-acting analogs (lonapegsomatropin, somapacitan, somatrogon) reduce injection frequency. Approved indications and safety are defined by each product's labeling; non-approved uses (such as athletic performance or anti-aging) are not supported and are specifically restricted by federal law.
Notes: Somatropin is FDA-approved and marketed as a biologic under many brands. As a recombinant protein biologic it is not eligible for pharmacy compounding under 503A or 503B. Growth hormone carries a distinctive federal restriction: under the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 333(e)), distributing or possessing growth hormone for any use other than an FDA-approved indication (for example, bodybuilding or anti-aging) is a federal crime. It is not a DEA-scheduled controlled substance but is subject to that special restriction, and it is prohibited in sport (WADA).
International status
Pharmacokinetics
Storage and handling
Important Notes
Practical considerations for consistency and safety.
- HGH 191AA is a genuinely FDA-approved biologic (somatropin), unlike most research peptides on this site.
- The '191AA' label distinguishes modern somatropin from the older 192-amino-acid methionyl variant (somatrem).
- Distributing growth hormone for non-approved uses (bodybuilding, anti-aging) is a federal crime, not merely off-label.
- It cannot be legally compounded; only FDA-approved brand products are lawful.
- It is prohibited in sport (WADA) and requires monitoring for glucose intolerance and other effects.
Lifestyle Factors
- Used under endocrinologist supervision with monitoring of IGF-1, glucose, and thyroid function.
- Injection timing (often evening) is set per the treatment plan.
References
Related compounds
Important disclaimer
This page is an educational reference, not medical advice, a diagnosis, or a treatment recommendation, and not a substitute for your prescriber or pharmacist. Approval and regulatory status varies by compound and can change. Always confirm against current prescribing information and consult a qualified healthcare professional before making any decision about a medication.