HGH (Somatropin)
Human Growth Hormone | 191aa Recombinant Growth Hormone
On this page
What is HGH (Somatropin)?
HGH (somatropin) is a lab-made copy of the growth hormone the pituitary gland naturally produces — a 191-amino-acid protein matching the body's own hormone. It carries FDA-approved status for specific growth-hormone-deficiency conditions under physician supervision; researchers separately study broader, off-label effects on metabolism and body composition in the clinical literature. Material referenced in this entry is for laboratory and educational research use only, not for human or animal administration.
Key terms:
HGH (Somatropin) is a single-chain polypeptide with two disulfide bridges.
Human Growth Hormone (HGH), also known as somatropin or somatotropin, is a hormone the anterior pituitary gland makes naturally. It is a single chain of 191 amino acids. Recombinant HGH (rhGH/somatropin) is grown in engineered cells and is bioidentical to the body's own growth hormone. It is FDA-approved for growth hormone deficiency in children and adults, as well as several other conditions. The '191aa' designation refers to that complete 191 amino acid structure. It distinguishes the form from older 192aa formulations. HGH regulates growth, metabolism, body composition, and numerous other physiological processes. It acts both directly and by stimulating IGF-1 production.
Key research areas
- Clinical trials in approved-indication patients report improved body composition (increased lean mass, decreased fat mass)
- Associated with increased bone mineral density in clinical studies
- Associated with improved lipid profile in clinical studies
- Associated with increased exercise capacity in clinical studies
- Quality-of-life and mood measures studied in clinical trials
- Skin and hair changes reported in clinical literature
- Recovery and tissue-healing effects studied in off-label and clinical research
Researched dosing
This table reflects the dosing ranges reported in medical and research literature, from physician-supervised replacement therapy to off-label study protocols — presented as reference data, not personal usage instructions.
| Phase | Dose | Frequency | Route |
|---|---|---|---|
| GH-deficiency studies (starting) | 0.15-0.3 mg/day (0.5-1 IU) | Once daily | SubQ injection |
| GH-deficiency studies (maintenance) | 0.4-0.8 mg/day (1.2-2.4 IU) | Once daily | SubQ injection |
| Longevity studies (lower dose) | 1-2 IU/day (0.33-0.67 mg) | Once daily | SubQ injection |
| Body-composition studies (moderate) | 2-4 IU/day (0.67-1.33 mg) | Once or twice daily | SubQ injection |
| Performance studies (higher dose) | 4-8 IU/day (1.33-2.67 mg) | Split twice daily | SubQ injection |
| Fasted-morning protocol | 2-4 IU | Morning on empty stomach | SubQ injection |
Commonly cycled 24 weeks on, 0+ weeks off.
How it works
At the cell level, HGH research looks at how the hormone binds growth-hormone receptors to trigger signaling that influences cell growth and metabolism, both directly and indirectly through IGF-1 — the terms below are the names for those steps.
HGH binds to GH receptors on target tissues, triggering JAK2-STAT5 signaling pathway. Direct effects include lipolysis, protein synthesis stimulation, and metabolic regulation. Indirect effects occur via IGF-1 stimulation in liver and peripheral tissues, promoting growth, cell proliferation, and anabolism. Half-life: ~3 hours subcutaneously; peak levels 3-5 hours post-injection.
Molecular data
These figures — molecular weight, 191-amino-acid sequence, disulfide bonds — are the chemistry ID researchers and pharmacists use to confirm a sample matches the structure of natural pituitary growth hormone.
- Weight
- 22124 Da
- Length
- 191 amino acids
- Type
- Single-chain polypeptide with two disulfide bridges
191 amino acid single-chain protein with 4 cysteine residues forming 2 intrachain disulfide bonds. Identical to endogenous pituitary-derived hGH
Pharmacokinetics
This chart shows how a dose of HGH is absorbed and cleared in the reported data — read it like a timer: levels peak a few hours after injection, then decline over the following day.
- Peak
- 4 hr
- Half-life
- 3 hrs
- Cleared
- ~15 hrs
Based on pharmacokinetic studies
Research applications
This section summarizes the conditions HGH is FDA-approved for under physician prescription, plus the broader off-label research areas scientists have studied — a summary of the clinical and research literature, not guidance for self-directed use.
Approved Uses
FDA-approved for children with GHD, including idiopathic and organic causes. Also approved for Turner syndrome, Prader-Willi syndrome, SGA, Noonan syndrome, SHOX deficiency, and chronic renal insufficiency. FDA-approved for adults with GHD from childhood-onset or adult-onset causes including pituitary tumors, surgery, radiation, or trauma. Requires biochemical confirmation. FDA-approved indication for treatment of HIV-associated wasting/cachexia to increase lean body mass and body weight.
Off Label Research
Off-label research applications for body composition and performance enhancement.
Body Composition
Research into body composition improvements including fat reduction and lean mass enhancement beyond approved indications.
Dosage reference
- Doses used in research
- Published protocols started at 1–2 IU daily before any increase.
- Frequency in studies
- Once daily (morning) or split AM/PM at higher doses
- Handling
- Reconstituted solution — research use only; not for administration
- Timeline reported in studies
- 1-2 weeks: improved sleep, energy; 4-8 weeks: fat reduction begins, skin improvement; 3-6 months: significant body composition changes, full benefits
- Storage
- Lyophilized: refrigerate 2-8°C; Reconstituted: refrigerate, use within 14-28 days; Never freeze
- Cycle length
- 3-6 months minimum for body composition; can be used long-term under medical supervision
- Break between cycles
- Some protocols cycle 5 days on/2 days off or take periodic breaks; medical replacement is typically continuous
Interactions
This list shows which other hormones and metabolic compounds are studied alongside HGH in the clinical and research literature, and flags combinations that need monitoring.
Reconstitution & storage
This is the standard laboratory method for turning freeze-dried HGH powder into a liquid research solution — a multi-step process due to its larger protein structure.
- Remove HGH vial from refrigerator and allow to reach room temperature (15-20 minutes)
- Clean the rubber stopper of both HGH vial and BAC water with alcohol swab
- Determine reconstitution volume - common: 1 mL BAC water per 10 IU vial (each 0.1 mL = 1 IU)
- Draw bacteriostatic water into syringe slowly, removing all air bubbles
- Insert needle into HGH vial at angle, aiming stream at vial wall - NOT directly on powder
- Inject BAC water slowly down the inside wall of the vial - drop by drop
- Remove needle and gently swirl vial in circular motion - NEVER SHAKE
- Allow to sit if any cloudiness, then swirl again until completely clear
- Solution should be crystal clear - discard if cloudy or contains particles
- Label vial with reconstitution date and concentration
Lyophilized: 2-8°C, use within As per manufacturer; refrigerate immediately upon receipt
Reconstituted: 2-6°C, use within 14-28 days depending on product; never freeze
Quality indicators
These are the checks researchers and pharmacists use to confirm an HGH sample is pure, correctly folded, and free of degradation — a quick reference against a Certificate of Analysis (COA), most relevant for pharmaceutical-grade material.
White lyophilized powder/cake - Should appear as white to off-white powder or solid cake - not liquid or collapsed
Crystal clear reconstituted solution - After proper reconstitution, solution must be completely clear and colorless with no particles
Vacuum intact in sealed vial - Properly sealed vials should show resistance when inserting needle due to vacuum
Pharmaceutical grade with COA - Pharmaceutical brands (Genotropin, Norditropin, Humatrope) preferred; research grade should have certificate of analysis
Generic/underground lab products - Vary significantly in quality and potency. Third-party testing recommended. Common counterfeits exist
Cloudy, discolored, or particles visible - Any cloudiness, yellow/brown color, or floating particles indicates degradation - do not use
Powder appears melted or stuck to vial - Indicates improper storage/temperature exposure - peptide likely degraded
What to expect
This timeline summarizes what the clinical and research literature reports at each study stage — research context for comparing studies, not a personal-results promise.
Improved sleep quality, increased energy, possible water retention and joint stiffness
Enhanced recovery from exercise, skin beginning to improve, possible numbness/tingling in hands (carpal tunnel symptoms)
Noticeable fat reduction beginning (especially abdominal), improved skin elasticity and texture
Continued fat reduction, lean mass improvements, hair/nail growth, reduced recovery time
Significant body composition changes, improved bone density markers, sustained energy and well-being
Maintained benefits with ongoing use; effects diminish over weeks-months after discontinuation
Safety notes
This section covers HGH's regulatory status, prescribing restrictions, and contraindications drawn from clinical literature — reference information for research and education, not medical advice.
- Contraindicated with active cancer - GH may accelerate tumor growth
- Contraindicated in acute critical illness - increased mortality shown in ICU patients
- Do not use for growth promotion in children with closed epiphyses
- Not recommended during pregnancy or breastfeeding
- Monitor blood glucose - HGH causes insulin resistance and can unmask or worsen diabetes
- Monitor thyroid function - can unmask hypothyroidism; may require T4 supplementation
- FDA-approved only for specific medical conditions - off-label use carries legal and health risks
- Long-term high-dose use associated with acromegaly-like side effects (enlarged features, organ growth)
Regulatory status
- Approved by the FDA for at least one indication. That approval applies to regulated pharmaceutical products, not to research-grade material.
- Supplied and described for laboratory research use only — not for human or veterinary use.
Community data
Community Insights
Based on data the community reported. Not clinical proof.
References
Largest long-term safety study of GH replacement showing de novo cancer incidence comparable to general population (SIR 0.92). Supports safety of long-term GH replacement in routine clinical practice.
Positive effects demonstrated on cardiovascular surrogate markers and bone metabolism. Suggests potential positive effect on CVD and fracture risk.
Established the syndrome of adult GH deficiency: decreased exercise tolerance, reduced mood/well-being, increased central adiposity, hyperlipidemia, reduced bone density, and atherogenesis predisposition.