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Growth hormone axis

Somatropin (rhGH)

Also known as recombinant human growth hormone, rhGH, hGH, Norditropin, Zomacton

FDA-approved productTier A applies to the adult GHD label layer for licensed products only. The reviews cited do not support non-GHD use (anti-aging, athletic), and 21 U.S.C. 333(e) restricts it. If the formulary vial is not a licensed product, the label evidence does not describe it.

Recombinant human growth hormone (polypeptide hormone replacement)

FDA-approved as Norditropin and Zomacton. Compounded somatropin is not FDA-approved. Source, Jul 2025

Identity. Somatropin is recombinant human growth hormone (rhGH). The formulary product is a 10 mg vial. Conversion: 1 mg anhydrous somatropin = 3.0 USP Somatropin Units (IU). Write every dose in mg, and show IU only beside its mg equivalent. Somatropin products are licensed biologics (Norditropin: Biologic Licensing Application, U.S. License No. 1261). Whether the formulary vial is an FDA-licensed product (for example, Zomacton 10 mg) or a compounded or repackaged vial is not established. The label dosing below describes licensed products only.

At a glance

These dosages are a helpful guide, not a prescription. Every clinician is expected to do their own due diligence before prescribing.

  1. Start

    0.2 mg/day (range 0.15 to 0.3), subcutaneous, adult GHD non-weight-based12

    Approved label

  2. Ceiling

    weight-based max: 0.016 mg/kg daily (Norditropin), 0.0125 mg/kg daily (Zomacton)12

    Approved label
Frequency
daily12
Route
subcutaneous to the back of the upper arm, abdomen, buttocks, or thigh1
Course
ongoing; dose reviewed every 1-2 months during titration1
If reconstituted to 10 mg/mL, 0.2 mg is 0.02 mL (2 U-100 marks), about 0.6 IU; dose in mg, never syringe units.
Calculate this dose

Dosing detail

Approved label

Approved label

  • Norditropin label, adults with growth hormone deficiency, non-weight-based regimen, starting dose

    0.2 (range 0.15 to 0.3) mg/day1

    Route
    subcutaneous
    Frequency
    daily
    Duration
    ongoing; dose reviewed every 1-2 months during titration
    n
    not applicable
    Design
    FDA-approved labeling (DailyMed, revised 7/2025)
    Source quote
    Initiate NORDITROPIN with a dose of approximately 0.2 mg/day (range, 0.15 mg/day to 0.3 mg/day)

    Finding. The label starting dose for adult GHD. Decrease the dose for adverse reactions or IGF-1 above the age- and sex-specific normal range.

  • Norditropin label, adults with GHD, titration step

    0.1 to 0.2 (increment) mg/day1

    Route
    subcutaneous
    Frequency
    daily; increase every 1-2 months
    Duration
    ongoing
    n
    not applicable
    Design
    FDA-approved labeling (DailyMed, revised 7/2025)
    Source quote
    increase the dose every 1-2 months by increments of approximately 0.1 mg/day to 0.2 mg/day

    Finding. Titration is guided by clinical response and serum IGF-1.

  • Norditropin label, adults with GHD, weight-based regimen: start 0.004 mg/kg daily, maximum 0.016 mg/kg daily

    0.004 (start); 0.016 (maximum) mg/kg daily1

    Route
    subcutaneous
    Frequency
    daily
    Duration
    ongoing
    n
    not applicable
    Design
    FDA-approved labeling (DailyMed, revised 7/2025)
    Source quote
    Initiate NORDITROPIN at 0.004 mg/kg daily and increase the dose according to individual patient requirements

    Finding. The weight-based start is 0.004 mg/kg daily, titrated to a maximum of 0.016 mg/kg daily. The label says: "Not recommended for obese patients as they are more likely to experience adverse reactions with this regimen". For geriatric patients: "Consider using a lower starting dose and smaller dose increment increases for geriatric patients".

  • Norditropin label, administration site and technique

    not applicable not applicable1

    Route
    subcutaneous to the back of the upper arm, abdomen, buttocks, or thigh
    Frequency
    daily
    Duration
    ongoing
    n
    not applicable
    Design
    FDA-approved labeling (DailyMed, revised 7/2025)
    Source quote
    Administer NORDITROPIN by subcutaneous injection to the back of the upper arm, abdomen, buttocks, or thigh

    Finding. Rotate injection sites to avoid lipoatrophy.

  • Zomacton label, adults with GHD, non-weight-based regimen, starting dose

    0.2 (range 0.15 to 0.3) mg/day2

    Route
    subcutaneous
    Frequency
    daily
    Duration
    ongoing; dose reviewed every 1 to 2 months during titration
    n
    not applicable
    Design
    FDA-approved labeling (openFDA label record)
    Source quote
    Initiate ZOMACTON with a dose of approximately 0.2 mg/day (range, 0.15 mg/day to 0.3 mg/day)

    Finding. Same non-weight-based start as the Norditropin label. Route per the label: "Administer ZOMACTON by subcutaneous injection to the back of the upper arm, abdomen, buttock, or thigh".

  • Zomacton label, adults with GHD, non-weight-based titration step

    0.1 to 0.2 (increment) mg/day2

    Route
    subcutaneous
    Frequency
    daily; increase every 1 to 2 months
    Duration
    ongoing
    n
    not applicable
    Design
    FDA-approved labeling (openFDA label record)
    Source quote
    increase the dose every 1 to 2 months by increments of approximately 0.1 mg/day to 0.2 mg/day

    Finding. No fixed maximum is stated for the non-weight-based regimen in the cited label excerpt.

  • Zomacton label, adults with GHD, weight-based regimen start and maximum

    0.006 (start); 0.0125 (maximum) mg/kg daily2

    Route
    subcutaneous
    Frequency
    daily
    Duration
    ongoing
    n
    not applicable
    Design
    FDA-approved labeling (openFDA label record)
    Source quote
    Initiate ZOMACTON at 0.006 mg/kg daily

    Finding. The weight-based start is 0.006 mg/kg daily, with a label maximum of 0.0125 mg/kg daily ("to a maximum of 0.0125 mg/kg daily"). Each product's own label governs.

Human studies

Human study

  • Adults with GH deficiency, individualized dose titration arm (ID)

    0.2 start, +0.2 increments, maximum 0.8 mg/d3

    Route
    not stated in abstract
    Frequency
    daily (mg/d)
    Duration
    32 weeks
    n
    387 (ID 187, FD 200)
    Design
    Randomized, individualized titration vs fixed weight-based dosing
    Source quote
    ID was started at 0.2 mg/d and increased by 0.2-mg/d increments, based on clinical and serum IGF-I responses, to a maximum of 0.8 mg/d.

    Finding. Efficacy and IGF-1 rise were similar with the lower final dose, and peripheral edema was less frequent (9.1% vs 16.5%) in the individualized arm than in the fixed-dose arm.

  • Adults with GH deficiency, fixed weight-based dosing arm (FD)

    4, then 8, then 12 microg/kg.d3

    Route
    not stated in abstract
    Frequency
    daily (microg/kg.d)
    Duration
    32 weeks
    n
    387 (ID 187, FD 200)
    Design
    Randomized, individualized titration vs fixed weight-based dosing
    Source quote
    In FD, subjects received sequentially 4, 8, and 12 microg/kg.d GH.

    Finding. The final GH dose was higher in the fixed-dose arm than in the individualized arm (0.70 vs 0.54 mg/d), with similar IGF-1 increases.

  • Elderly (60-79 yr) patients with multiple pituitary hormone deficiencies and GH deficiency, Humatrope

    0.05 IU/kg/week for 1 month, then 0.1 IU/kg/week (0.75-1.25 IU/day); about 0.017 mg/kg/week then 0.033 mg/kg/week (about 0.25-0.42 mg/day) at 3.0 IU per mg IU/kg x week (mg equivalent computed at 1 mg = 3.0 USP units; older trials may have used an earlier reference standard, so the mg figure is approximate)4

    Route
    sc (subcutaneous), per abstract
    Frequency
    divided into daily injections
    Duration
    6 months placebo-controlled, then 12 months open treatment
    n
    31
    Design
    Randomized, double-blind, placebo-controlled, then open-label
    Source quote
    The dose was 0.05 IU/kg x week for 1 month, and after that it was 0.1 IU/kg x week divided into daily sc injections (0.75-1.25 IU/day).

    Finding. Lean body mass improved and fat mass fell modestly. Side effects were mild and mostly from fluid retention.

  • NON-GHD POPULATION, NOT A RECOMMENDATION: Healthy community-dwelling elderly (mean age 69), systematic review of randomized trials, not GHD

    mean initial daily dose 14 (SD 7) microg per kg of body weight5

    Route
    not stated in abstract
    Frequency
    daily (initial daily dose)
    Duration
    mean 27 weeks (SD 16)
    n
    220 participants who received GH completed their studies
    Design
    Systematic review and meta-analysis of randomized controlled trials
    Source quote
    Initial daily GH dose (mean, 14 microg per kg of body weight [SD, 7]) and treatment duration (mean, 27 weeks [SD, 16]) varied.

    Finding. Fat mass fell and lean mass rose by about 2 kg each. Participants had more edema, arthralgias, carpal tunnel syndrome, gynecomastia, and diabetes or impaired fasting glucose. The review concluded GH cannot be recommended for anti-aging.

  • NON-GHD POPULATION, NOT A RECOMMENDATION: Healthy, young (13-45 yr), physically fit adults, athletic performance, systematic review of randomized trials, not GHD

    mean 36 (SD 21) microg/kg per day6

    Route
    not stated in abstract
    Frequency
    daily
    Duration
    mean 20 days (SD 18) for studies giving GH for more than 1 day
    n
    303 participants received GH
    Design
    Systematic review of randomized controlled trials
    Source quote
    Growth hormone dosage (mean, 36 microg/kg per day [SD, 21]) and treatment duration (mean, 20 days [SD, 18] for studies giving growth hormone for >1 day) varied.

    Finding. Lean body mass rose 2.1 kg, but strength and exercise capacity did not improve. Participants had more soft tissue edema and fatigue.

Clinical practice

Clinical practice

No cited source reports what clinicians commonly use outside the labeled GHD indication (start, typical, ceiling, timing, cycle). The sources above are guideline and trial statements about adult GHD, not off-label practice. No practice values are established.

Sources

  • Clinical practicePeer-reviewed study3
    We conclude that GH replacement therapy should be initiated at a low dose and titrated to a dose producing maximal benefits without adverse side effects and an IGF-I level within the age- and sex-adjusted normal range.
  • Clinical practiceGuideline7
    GH dosing regimens should be individualized.
  • Clinical practicePeer-reviewed study4
    As long-term risks are unknown, GH doses should be titrated to keep IGF-I within the age-related physiological range.

Safety

Serious warnings

  • No boxed warning appears in the Norditropin prescribing information (DailyMed, rev. 7/2025).1
  • Norditropin label warnings and precautions: increased mortality in acute critical illness (5.1); sudden death in Prader-Willi syndrome (5.2); neoplasms (5.3); glucose intolerance and diabetes mellitus (5.4); intracranial hypertension (5.5); severe hypersensitivity (5.6); fluid retention (5.7); hypoadrenalism (5.8); hypothyroidism (5.9); slipped capital femoral epiphysis (5.10); progression of preexisting scoliosis (5.11); pancreatitis (5.12); lipoatrophy (5.13); laboratory tests (5.14).1
  • Landmark RCT (Takala 1999, two parallel trials, 247 Finnish and 285 other European ICU patients, GH about 0.10 mg/kg/day): in-hospital mortality was 39% vs 20% (Finnish) and 44% vs 18% (multinational). The relative risk of death was 1.9 and 2.4. This is the evidence behind the critical-illness warning and contraindication.8

Contraindications

  • Norditropin Section 4 contraindications: "Acute critical illness after open heart surgery, abdominal surgery or multiple accidental trauma" (the item also covers acute respiratory failure); "Pediatric patients with Prader-Willi syndrome who are severely obese" (the item also covers upper airway obstruction or sleep apnea history, or severe respiratory impairment); "Active Malignancy"; "Hypersensitivity to NORDITROPIN or any of its excipients."; "Active proliferative or severe non-proliferative diabetic retinopathy."; "Pediatric patients with closed epiphyses." The Prader-Willi contraindication applies to pediatric patients only.1

Adverse effects

  • In the Norditropin adult GHD placebo-controlled trial, peripheral edema occurred in 42% of treated patients vs 8% on placebo, and edema in 25% vs 0%. Common reactions across adults and children included upper respiratory infection, fever, pharyngitis, headache, otitis media, edema, arthralgia, paresthesia, myalgia and impaired glucose tolerance.1
  • In a systematic review of healthy elderly adults, GH recipients had significantly more soft tissue edema, arthralgias, carpal tunnel syndrome and gynecomastia, and were somewhat more likely to develop diabetes mellitus or impaired fasting glucose.5
  • In a systematic review of young fit adults, GH recipients more often had soft tissue edema and fatigue.6
  • In the individualized-dose trial, peripheral edema was less frequent with titration than with fixed weight-based dosing (9.1% vs 16.5%, P = 0.03), and so was rash (1.1% vs 5.5%).3
  • Tumor risk: the 2007 GH Research Society consensus states there is no evidence that GH replacement increases the risk of tumor recurrence or de novo malignancy. The label still lists neoplasms as a warning and active malignancy as a contraindication.9

Monitoring

  • Titrate on clinical response and serum IGF-1. Reduce the dose for adverse reactions or IGF-1 above the age- and sex-specific normal range (Norditropin label).1
  • GH Research Society consensus: assess response clinically by monitoring biochemistry, body composition and quality of life. A low IGF-1 is a reliable diagnostic indicator of GHD in the presence of hypopituitarism, but a normal IGF-1 does not rule out GHD.9
  • Thyroid (5.9): "patients should have periodic thyroid function tests".1
  • Glucose (5.4): "Monitor glucose levels periodically in all patients receiving NORDITROPIN".1
  • Eyes (5.5): "Funduscopic examination should be performed routinely before initiating treatment with NORDITROPIN".1
  • Adrenal (5.8): "Monitor patients for reduced serum cortisol levels and/or need for glucocorticoid dose increases".1

Interactions

  • Glucocorticoids: Norditropin inhibits 11beta-HSD-1 and may lower serum cortisol. Patients on glucocorticoid replacement may need higher maintenance or stress doses. Pharmacologic glucocorticoids may attenuate growth in pediatric patients.1
  • Oral estrogen: the label states "Patients receiving oral estrogen replacement may require greater NORDITROPIN dosages."1
  • Insulin and other hypoglycemic agents: GH may reduce insulin sensitivity, so dose adjustments may be needed. CYP450-metabolized drugs: clearance may change, so monitor carefully.1

Handling

Reconstitution

Zomacton 10 mg vial (label): reconstitute with the supplied 1 mL syringe of Bacteriostatic Water for Injection, USP with 0.33% metacresol. The resulting concentration is 10 mg in 1 mL = 10 mg/mL, so 0.2 mg = 0.02 mL and 0.1 mg = 0.01 mL (2 and 1 marks on a U-100 insulin syringe). Write doses in mg and mL, never in syringe 'units' or IU without the conversion (0.2 mg is about 0.6 IU, not 2 IU). Volumes this small are hard to measure at 10 mg/mL. These are the approved product's instructions. A compounded vial may differ, so take diluent volume and concentration from the partner pharmacy's label.

Storage before mixing

Zomacton vials: refrigerate at 36 to 46 F (2 to 8 C) in the original carton to protect from light. The label's freeze warning applies to the accompanying diluent ("Avoid freezing the accompanying diluent"). Norditropin unused pens: refrigerate at 36 to 46 F (2 to 8 C).

Storage after mixing

Zomacton 10 mg vial after reconstitution: refrigerate at 2 to 8 C (36 to 46 F) for up to 28 days (5 mg vial: up to 14 days). Do not freeze.12

Evidence

Evidence is strong for adult growth hormone deficiency. FDA-approved somatropin labels give start, titration and maximum doses. Randomized trials and society guidelines support a low start with IGF-1-guided titration. In healthy adults (anti-aging, athletic use), the systematic reviews found small body-composition changes with more adverse events, and they do not support use. No source gives a citable off-label practice dose.

Mechanism

Somatropin replaces endogenous growth hormone in its labeled indications. The Norditropin label indication is replacement of endogenous GH in adults with GHD. Per the label, it inhibits 11beta-HSD-1 and may lower serum cortisol. The label and guidelines follow dose response with serum IGF-1 and use it for titration.1

Availability

Amounts offered

  • 10 mg

Custom strengths on request.

References

According to PubMed

  1. 1NORDITROPIN (somatropin) injection, solution, prescribing informationDailyMed, NLM (label revised 7/2025; set id 1058e17c-9261-459c-a3e6-fae38d196c14), 2025
  2. 2ZOMACTON (somatropin) for injection, label recordopenFDA drug label API; DailyMed set id 85ba081b-bee0-4a9a-aa0f-ae5b5e9a0886, effective time 20260420, 2026
  3. 3Efficacy and tolerability of an individualized dosing regimen for adult growth hormone replacement therapy in comparison with fixed body weight-based dosingJ Clin Endocrinol Metab 89(7):3224-33, 2004
  4. 4Growth hormone replacement therapy improves body composition and increases bone metabolism in elderly patients with pituitary diseaseJ Clin Endocrinol Metab 85(11):4104-12, 2000
  5. 5Systematic review: the safety and efficacy of growth hormone in the healthy elderlyAnn Intern Med 146(2):104-15, 2007
  6. 6Systematic review: the effects of growth hormone on athletic performanceAnn Intern Med 148(10):747-58, 2008
  7. 7Evaluation and treatment of adult growth hormone deficiency: an Endocrine Society clinical practice guidelineJ Clin Endocrinol Metab 96(6):1587-609, 2011
  8. 8Increased mortality associated with growth hormone treatment in critically ill adultsN Engl J Med 341(11):785-92, 1999
  9. 9Consensus guidelines for the diagnosis and treatment of adults with GH deficiency II: a statement of the GH Research SocietyEur J Endocrinol 157(6):695-700, 2007
  10. 10USP monograph: SomatropinUSP 35 (via drugfuture.com), 2012
  11. 11Notice to Compounders: Changes that affect compounding as of March 23, 2020U.S. FDA, 2020
  12. 1221 U.S.C. 333(e)Cornell LII

Last reviewed 2026-10-14. 41 figures checked against their sources. How this works