HGH 191AA: Side Effects

Safety Notice#

The safety profile of HGH 191AA in humans has not been established through controlled clinical trials. The information below is derived primarily from animal studies and should be interpreted accordingly.

Documented Adverse Effects#

We defined HGH 191AA as recombinant human growth hormone identical to the native 191–amino‑acid sequence (somatropin). We summarize animal toxicology and human adverse effects below, with frequency and severity where available, followed by a consolidated table.

Animal studies Across standard acute and subacute toxicology programs, somatropin showed high tolerability at supratherapeutic doses in multiple species. In mice and rats, single subcutaneous or intravenous doses of 12.5 mg/kg (≈200-fold the human daily dose) produced no deaths and only transient leg weakness after IV dosing in mice; 30‑day dosing at 0.125–3.125 mg/kg/day in rodents detected no toxicologically significant changes (hematology, chemistry, organ weights). In rhesus monkeys, daily intramuscular doses for 5 weeks at 0.125–1.25 mg/kg/day (up to ~20× anticipated human daily dose) produced no treatment‑related abnormalities and no anti‑somatropin antibodies; by contrast, methionyl‑GH elicited antibodies under similar conditions. No genotoxicity was detected. Anabolic bone effects were observed in rats at extremely high doses (400 mg/kg twice daily ×28 days), consistent with pharmacology.

Human adverse effects and side effects Common, dose‑related effects reflect GH pharmacology (fluid retention, soft‑tissue growth) and are typically mild–moderate and reversible with dose reduction or interruption.

• Edema and peripheral edema: In a randomized adult trial, edema occurred in 17.3% on somatropin vs 4.4% on placebo; peripheral edema 11.5% vs 0%. Usually mild–moderate; respond to dose reduction (standardUnknownyearbiosynthetichumangrowth pages 16-18).
• Arthralgia/myalgia: Adults commonly report musculoskeletal pain; label frequency brackets indicate arthralgia ≥10% in adults; pediatric ISS trial reported myalgia 24.3% vs 12.9% with placebo (standardUnknownyearbiosynthetichumangrowth pages 13-16, standardUnknownyearbiosynthetichumangrowth pages 16-18).
• Carpal tunnel syndrome/paresthesia: Generally ≥1%–<10% on labels; two of 113 adult‑onset GHD patients developed carpal tunnel after maintenance therapy; typically improves with dose reduction (standardUnknownyearbiosynthetichumangrowth pages 13-16, standardUnknownyearbiosynthetichumangrowth pages 16-18).
• Injection‑site reactions: Local reactions including pain, erythema, and lipoatrophy occur in ≈1%–<10% overall; pediatric injection‑site pain 6.7% in one cohort (saizen2012prsaizen®click. pages 13-16, standardUnknownyearbiosynthetichumangrowth pages 13-16).

Less common but clinically important

• Intracranial hypertension (pseudotumor cerebri): Very rare (≤0.1% on labels), usually within the first ~8 weeks; presents with headache, visual symptoms, papilledema; reversible with dose reduction/cessation (standardUnknownyearbiosynthetichumangrowth pages 13-16, saizen2012prsaizen®click. pages 7-10).
• Glucose intolerance/diabetes: Adults show increases in fasting insulin and glucose; mean fasting insulin rose ≈10% in one adult series; label frequencies: pediatric hyperglycemia <1%, adults ≥1%–<10%. Risk higher in predisposed patients; monitor and titrate slowly (standardUnknownyearbiosynthetichumangrowth pages 16-18, standardUnknownyearbiosynthetichumangrowth pages 13-16).
• Thyroid effects: GH can increase peripheral T4→T3 conversion and unmask central hypothyroidism; labels and guidelines recommend routine thyroid function monitoring (standardUnknownyearbiosynthetichumangrowth pages 13-16, saizen2012prsaizen®click. pages 7-10).
• Scoliosis progression: Reported in ≥1%–<10% of pediatric patients; often reflects rapid growth; monitor clinically (standardUnknownyearbiosynthetichumangrowth pages 13-16).
• Slipped capital femoral epiphysis (SCFE): Rare; reported in trials and postmarketing, sometimes prompting discontinuation; presents with hip/knee pain or limp.
• Gynecomastia: Reported in pediatric ISS RCTs (5.4% vs 3.2% placebo); usually mild (standardUnknownyearbiosynthetichumangrowth pages 16-18).
• Rash/hypersensitivity: Hypersensitivity to formulation components occurs in ≈1%–<10%; anaphylaxis is very rare (standardUnknownyearbiosynthetichumangrowth pages 13-16, saizen2012prsaizen®click. pages 13-16).
• Pancreatitis: Rare case reports; counsel on abdominal pain and evaluate if symptoms arise (saizen2012prsaizen®click. pages 7-10).

Long‑term safety signals (malignancy and vascular events)

• Malignancy/second neoplasms: In the large pediatric NCGS registry (~55,000 patients), 49 secondary malignancies were observed, ≈4.6 per 1000 patient‑years of exposure. For new primary malignancy in patients without known risk factors, the standardized incidence ratio was ~1.12 (95% CI 0.75–1.61), not significantly elevated. Increased risk is most evident among childhood cancer survivors with prior cranial irradiation (e.g., meningioma); labels warn accordingly.
• Cardiovascular/cerebrovascular events: No conclusive increase at replacement dosing has been established; surveillance data emphasize monitoring in higher‑risk populations. Supraphysiologic dosing in critically ill adults increased mortality and is contraindicated; replacement dosing practices now use lower, titrated doses (contextual safety information).

Immunogenicity Binding antibodies to somatropin occur infrequently: ≈1.6% within 6 months, with only 0.6% exceeding 2 mg/L over 8 years in one dataset; clinical impact is generally minimal (standardUnknownyearbiosynthetichumangrowth pages 13-16).

Embedded summary table

Key takeaways

• Animal toxicology: acute and subacute studies in mice/rats/dogs and rhesus monkeys showed high‑dose tolerance (single SC/IV up to 12.5 mg/kg with no deaths; 30‑day dosing up to 3.125 mg/kg/day in rodents and up to 1.25 mg/kg/day in monkeys without toxicologically significant findings)
• Common human AEs: fluid retention/edema (~17% treated vs ~4% placebo in an adult trial), peripheral edema (~11–12%), arthralgia ≥10% in adults; injection‑site reactions ~1%–<10% (standardUnknownyearbiosynthetichumangrowth pages 16-18, standardUnknownyearbiosynthetichumangrowth pages 13-16)
• Rare but important human AEs: benign intracranial hypertension/pseudotumor cerebri (≤0.1%), slipped capital femoral epiphysis (SCFE) reported rarely and may require discontinuation, pancreatitis rare
• Metabolic and endocrine effects: can increase insulin resistance/fasting insulin (mean fasting insulin ↑ ≈10%; pediatric hyperglycemia <1%, adults ~1%–<10%) and may unmask central hypothyroidism—monitor glucose and thyroid function (standardUnknownyearbiosynthetichumangrowth pages 16-18, saizen2012prsaizen®click. pages 13-16)
• Malignancy / second neoplasms: registry data identified 49 secondary malignancies (~4.6 cases per 1000 patient‑years); standardized incidence ratio (SIR) ≈1.12 (95% CI 0.75–1.61) for patients without known risk factors; excess risk concentrated in prior‑cranial‑irradiation survivors—causality remains uncertain
• Immunogenicity: binding antibodies reported in ~1.6% within 6 months and low long‑term titres in a small fraction; clinical impact generally low but monitored (standardUnknownyearbiosynthetichumangrowth pages 13-16)

Blockquote: Concise, source‑cited bullets summarizing animal toxicology (species/doses/NOAEL) and the main human adverse effects for recombinant 191‑aa growth hormone (somatropin), including frequencies and severity notes for clinicians and researchers.

Notes on severity

• Most common events (fluid retention, arthralgia, paresthesias) are Grade 1–2 and dose‑dependent; severity generally mitigated by dose reduction or temporary interruption (standardUnknownyearbiosynthetichumangrowth pages 16-18, standardUnknownyearbiosynthetichumangrowth pages 13-16).
• Serious AEs include intracranial hypertension, SCFE, pancreatitis, and second neoplasms in predisposed populations; these require prompt evaluation and treatment cessation as indicated.

Animal Study Safety Data#

HGH 191AA corresponds to somatropin, recombinant human growth hormone consisting of 191 amino acids. I summarize toxicological data with emphasis on LD50, organ/systemic toxicity in animals (acute and repeat dose), mutagenicity/genotoxicity, reproductive and developmental findings, carcinogenicity, and dose–response/NOAEL relationships, prioritizing regulatory product monograph content.

Summary table of key findings

Acute toxicity and LD50 Across six acute single-dose studies in mice, rats, and monkeys using subcutaneous, intravenous, and oral routes, somatropin produced minimal adverse effects at the highest doses tested; no LD50 was established. Doses included rats and mice up to 13.3 mg/kg SC or IV, rats up to 83.33 mg/kg SC, rats and mice 1.67–13.3 mg/kg orally, and monkeys 1.67–6.67 mg/kg SC; one monkey showed a minor histological change at 6.67 mg/kg SC (no mortality reported) (saizen2012prsaizen®click. pages 67-69, saizen2012prsaizen®click. pages 69-72).

Repeat‑dose toxicity and target organ findings Four‑week studies: rats tolerated up to 3.33 mg/kg/day SC; slight, largely reversible hematologic and biochemical changes occurred at ~1.6–3.33 mg/kg/day. Monkeys tolerated ~1.6 mg/kg/day SC without major toxicity (saizen2012prsaizen®click. pages 69-72). Thirteen‑week studies: rats showed no overt drug‑attributable toxicity; in male monkeys, elevations of liver enzymes (GOT, GPT, γ‑GTP, LAP) occurred at 1.67 mg/kg/day SC, indicating a potential hepatic laboratory signal at higher exposures (saizen2012prsaizen®click. pages 69-72). Fifty‑two‑week studies: rats and monkeys had no treatment‑related deaths; rats developed high anti‑drug antibody levels by week 12 (a common finding with cross‑species exposure to human proteins) (saizen2012prsaizen®click. pages 69-72). Local tolerance: injection‑site reactions were generally mild and largely attributable to preservatives (metacresol/benzyl alcohol). Metacresol at 10 mg/mL was mildly irritant in rabbits; sensitization testing showed 40–50% positives and severe anaphylaxis with high‑dose metacresol formulations on intradermal challenge (saizen2012prsaizen®click. pages 69-72).

Mutagenicity/genotoxicity A standard genotoxicity battery was negative: Ames test, gene conversion, unscheduled DNA synthesis (UDS), chromosomal aberration assays, and in vivo micronucleus test showed no mutagenic activity (saizen2012prsaizen®click. pages 69-72).

Carcinogenicity The product monograph excerpts do not report dedicated carcinogenicity studies for somatropin. This is consistent with many endogenous protein therapeutics where lifetime rodent carcinogenicity testing is not always performed; no treatment‑related neoplasia signals were described in the repeat‑dose studies summarized (saizen2012prsaizen®click. pages 69-72). Given the absence of explicit data in the accessible excerpts, carcinogenicity conclusions are limited to “no findings reported in these sections.”

Reproductive and developmental toxicity In rats and rabbits given somatropin subcutaneously up to 3.33 mg/kg/day, no embryotoxicity or teratogenicity was observed, and no adverse effects on F0/F1 reproductive performance were detected. In rabbits dosed during organogenesis (0, 0.033, 0.33, 3.33 mg/kg/day for 13 days), the NOAEL for dams and fetuses was 3.33 mg/kg/day. Increases in parental and offspring body weight and food/water intake at ≥0.33–3.33 mg/kg/day were attributed to pharmacologic activity rather than toxicity (saizen2012prsaizen®click. pages 72-76).

Dose–response relationships and NOAEL/LOAEL Acute studies reached high single doses without lethality; therefore, no LD50 was defined (saizen2012prsaizen®click. pages 67-69). In repeat‑dose settings: rats tolerated 3.33 mg/kg/day for 4 weeks with only slight, reversible lab changes at ≥1.6 mg/kg/day; monkeys tolerated ~1.6 mg/kg/day for 4 weeks; at 13 weeks, male monkeys showed liver enzyme elevations at 1.67 mg/kg/day. In developmental studies, a NOAEL of 3.33 mg/kg/day was identified in rabbits. Increased body weight/food intake at ≥0.33–3.33 mg/kg/day represents a pharmacologic exposure–response rather than a toxicologically adverse effect (saizen2012prsaizen®click. pages 69-72, saizen2012prsaizen®click. pages 72-76, saizen2012prsaizen®click. pages 65-67).

Limitations The detailed carcinogenicity section was not available in the excerpts reviewed; none of the accessible sections reported carcinogenicity studies or findings. U.S. or EU prescribing information could further corroborate nonclinical findings but were not retrievable in this session; however, the Saizen product monograph provided comprehensive nonclinical data consistent with typical label sections for somatropin (saizen2012prsaizen®click. pages 69-72, saizen2012prsaizen®click. pages 72-76).

Conclusion Somatropin (HGH 191AA) shows low acute toxicity in rodents and non‑rodents with no defined LD50 at high single doses, limited repeat‑dose findings chiefly of mild, reversible clinical pathology changes in rats and liver enzyme elevations in male monkeys at the highest 13‑week dose, negative results across a full genotoxicity battery, and no adverse reproductive or developmental toxicity up to 3.33 mg/kg/day, where pharmacologic increases in body weight and intake are observed. Long‑term studies reported no treatment‑related deaths; local tolerability issues relate largely to preservative components. Carcinogenicity data were not provided in the accessible excerpts, and no positive carcinogenic signal was reported therein (saizen2012prsaizen®click. pages 67-69, saizen2012prsaizen®click. pages 69-72, saizen2012prsaizen®click. pages 72-76, saizen2012prsaizen®click. pages 65-67).

Contraindications#

Objective: Provide the known contraindications and drug interactions for HGH 191AA (recombinant human growth hormone; somatropin), including theoretical interactions based on mechanism of action, with exact or distilled label/guideline language and management guidance.

Contraindications

• Acute critical illness: Do not initiate somatropin in patients with acute critical illness related to cardiac or abdominal surgery, multiple trauma, or acute respiratory failure because increased mortality was observed; avoid initiation during ICU-level illness (standardUnknownyearbiosynthetichumangrowth pages 1-5).
• Active malignancy/neoplasia: Do not use or discontinue somatropin when there is any evidence of neoplastic activity, including intracranial tumor; begin only after anti‑tumor therapy is completed and remission is documented; discontinue if tumor recurs (standardUnknownyearbiosynthetichumangrowth pages 5-8). Guidelines similarly advise deferring GH until remission is documented, commonly after at least one year.
• Diabetic retinopathy: Contraindicated in active proliferative or severe non‑proliferative diabetic retinopathy (standardUnknownyearbiosynthetichumangrowth pages 5-8, standardUnknownyearbiosynthetichumangrowth pages 40-43).
• Prader–Willi syndrome with respiratory risk: Contraindicated/not indicated in PWS patients who are very obese or have severe breathing problems, history of upper airway obstruction or sleep apnea; deaths have been reported in such patients; evaluate for OSA/airway obstruction prior to therapy (standardUnknownyearbiosynthetichumangrowth pages 1-5, standardUnknownyearbiosynthetichumangrowth pages 5-8).
• Closed epiphyses: Do not use for growth promotion if epiphyses are closed; stop when adult height is reached (standardUnknownyearbiosynthetichumangrowth pages 5-8, standardUnknownyearbiosynthetichumangrowth pages 43-44).
• Hypersensitivity: Contraindicated in known hypersensitivity to somatropin or formulation components; patients sensitive to the diluent (metacresol or glycerin) should not receive the supplied diluent; discontinue immediately if serious allergic reactions occur (standardUnknownyearbiosynthetichumangrowth pages 5-8, standardUnknownyearbiosynthetichumangrowth pages 44-45, standardUnknownyearbiosynthetichumangrowth pages 43-44).
• Post–renal transplant: Discontinue from the time of renal transplantation until one year post‑transplant (standardUnknownyearbiosynthetichumangrowth pages 10-13).

Drug interactions and mechanistic cautions

• Glucocorticoids: Somatropin inhibits 11β‑HSD1 and may enhance CYP3A4 activity, potentially reducing serum cortisol by impairing activation of cortisone/prednisone and by increasing clearance; careful monitoring of serum cortisol is required and glucocorticoid replacement doses may need adjustment; supraphysiologic glucocorticoids may blunt GH response (standardUnknownyearbiosynthetichumangrowth pages 21-23, standardUnknownyearbiosynthetichumangrowth pages 5-8).
• Glycemic control and antidiabetics: Somatropin may decrease insulin sensitivity, unmask impaired glucose tolerance or diabetes, and has been associated with new‑onset type 2 diabetes; patients with diabetes may require adjustment of insulin and/or other anti‑hyperglycemics and close monitoring of glucose/HbA1c.
• Estrogens: Oral estrogens may reduce serum IGF‑I response to somatropin; patients on oral estrogen may require higher GH doses or a switch to transdermal estrogen to restore responsiveness. Label also notes reduced effectiveness of estrogen/oral contraceptives due to CYP3A induction by somatropin (see below) (standardUnknownyearbiosynthetichumangrowth pages 21-23, standardUnknownyearbiosynthetichumangrowth pages 43-44).
• CYP3A substrates: Somatropin can increase CYP3A activity and may reduce plasma concentrations/effectiveness of drugs metabolized by CYP3A such as cyclosporine, some anticonvulsants, and sex steroids (estrogens/oral contraceptives); monitor drug levels/clinical effect and adjust doses as needed (standardUnknownyearbiosynthetichumangrowth pages 21-23, standardUnknownyearbiosynthetichumangrowth pages 43-44).
• Thyroid axis: Somatropin increases extrathyroidal conversion of T4 to T3 and may unmask hypothyroidism; assess thyroid function at baseline and periodically, and adjust levothyroxine if needed (standardUnknownyearbiosynthetichumangrowth pages 8-10).

Mechanism-based theoretical interactions and cautions

• Additive fluid retention/edema: GH commonly causes fluid retention; coadministration with drugs that cause edema (e.g., thiazolidinediones) may increase edema risk; monitor for edema/carpal tunnel and adjust therapies accordingly (mechanistic rationale; GH’s sodium/water-retaining effects).
• Intracranial hypertension: GH has been associated with benign intracranial hypertension; agents linked to pseudotumor cerebri (e.g., high‑dose vitamin A/retinoids, tetracyclines) may theoretically increase risk; monitor for headache/visual changes and perform funduscopic exams if symptomatic (label warning on intracranial hypertension and funduscopic exams) (standardUnknownyearbiosynthetichumangrowth pages 8-10).
• Contraceptive reliability: Because somatropin may induce CYP3A, effectiveness of oral contraceptives could be reduced; consider alternative or back‑up contraception and monitor for breakthrough bleeding (standardUnknownyearbiosynthetichumangrowth pages 21-23, standardUnknownyearbiosynthetichumangrowth pages 43-44).
• Immunosuppressants: Reduced cyclosporine exposure due to increased CYP3A activity could risk rejection; monitor trough levels and adjust dosing (standardUnknownyearbiosynthetichumangrowth pages 21-23).

Clinical implementation notes

• Monitor IGF‑I and clinical response; titrate dose to maintain IGF‑I in age‑appropriate range and minimize adverse effects (standardUnknownyearbiosynthetichumangrowth pages 5-8).
• In patients with prior malignancy, coordinate with oncology; many guidelines allow GH once remission is sustained, often after at least 12 months.
• In PWS, screen for OSA and respiratory impairment and avoid GH if high‑risk features are present; manage weight and airway issues before considering GH (standardUnknownyearbiosynthetichumangrowth pages 1-5, standardUnknownyearbiosynthetichumangrowth pages 5-8).

This synthesis integrates exact product‑label language and guideline statements to delineate absolute/relative contraindications and clinically significant or mechanistically plausible interactions for somatropin (HGH 191AA).

Evidence Gaps#

• Human adverse event data is limited to anecdotal reports
• Systematic adverse event monitoring has not been conducted
• Drug interaction studies are incomplete
• Long-term safety profiles are unknown

Related Reading#

• HGH 191AA overview and research guide
• HGH 191AA dosing protocols
• HGH 191AA risks and legal status