Treatment of Growth Hormone Deficiency with Genotropin (Somatropin)
Recommended Dosing
For pediatric patients with confirmed growth hormone deficiency, Genotropin should be administered at 0.045-0.05 mg/kg body weight per day via daily subcutaneous injection at night. 1, 2, 3
Dose Calculation
- Calculate the exact daily dose based on current body weight: weight (kg) × 0.045-0.05 mg = daily dose 2
- For example, a 40 kg child requires 1.8 mg per day (40 kg × 0.045 mg/kg) 2
- In pubertal patients, higher weekly dosages up to 0.7 mg/kg divided daily may be used 3
- Adjust dose regularly as the child gains weight 1
Administration Technique
Injections must be given subcutaneously at night, preferably before bedtime, to mimic physiological growth hormone secretion patterns. 1, 2
Injection Sites
- Rotate daily among: thighs, abdomen, buttocks, or upper outer arms 2, 3
- Daily rotation is mandatory to prevent lipoatrophy (loss of subcutaneous fat at injection sites). 1, 2
Monitoring Requirements
Clinical consultations every 3-6 months are required to assess treatment response and safety. 1, 2
Parameters to Monitor at Each Visit
- Height and growth velocity 1, 2
- Pubertal development (Tanner staging for children >10 years) 4
- Weight for dose adjustment 1
- Thyroid function (TSH and free T3) 1, 2
- Metabolic parameters: blood glucose, calcium, phosphate, bicarbonate 1, 2
Annual Assessments
Baseline Evaluation Before Starting
Absolute Contraindications
Do not initiate Genotropin in patients with: 4, 1
- Closed epiphyses 4, 1, 3
- Active malignancy 4, 1
- Acute critical illness 4, 1
- Known hypersensitivity to somatropin or excipients 4, 1
- Severe secondary hyperparathyroidism (PTH >500 pg/ml) 4, 1
- Proliferative or severe non-proliferative diabetic retinopathy 4
Assessment of Treatment Response
An adequate growth response is defined as height velocity increase >2 cm/year above baseline during the first year of treatment. 4
If Response is Inadequate (<2 cm/year increase)
Evaluate the following in order: 4, 1
- Patient adherence - verify daily injections are being administered 4
- Serum IGF-1 levels - confirm adequate absorption 4, 1
- Weight-adjusted dosing - recalculate dose based on current weight 4, 1
- Nutritional status - address malnutrition or metabolic abnormalities 4, 1
Do not increase the dose above recommended range in non-responders, as higher doses are not more effective. 4
When to Discontinue Treatment
Terminate Genotropin therapy in the following situations: 4, 1
Mandatory Discontinuation
- Epiphyseal closure confirmed on radiography 4, 1
- Height velocity <2 cm/year in late-pubertal adolescents 4
- Active malignancy develops 4, 1
- Severe adverse effects occur 4
- Confirmed slipped capital femoral epiphysis 4
- Intracranial hypertension develops 1, 2
Consider Discontinuation
- No adequate response after 6 months despite optimal adherence and metabolic control 4
- Patient reaches genetic target height 4, 1
- Unexplained decrease in renal function (if applicable) 4
- Evidence of accelerated bone maturation 4
Important Safety Considerations
Glucose Metabolism
- Monitor for glucose intolerance, especially in obese patients 1, 2
- Insulin secretion increases during treatment 2
Intracranial Hypertension
- Perform baseline fundoscopy before initiating therapy 1, 2
- Evaluate immediately if persistent headache or vomiting occurs 1, 2
- This is rare but requires prompt recognition 1
Orthopedic Complications
- Obtain radiographs if symptoms of slipped capital femoral epiphysis develop (hip or knee pain, limping) 4
- Monitor for scoliosis progression 1
Endocrine Effects
- Secondary hyperparathyroidism may worsen with treatment 2
- Hypothyroidism can develop or worsen during therapy 1
Special Populations
Chronic Kidney Disease
- Weekly dosage up to 0.35 mg/kg divided into daily injections 3
- Stop treatment at time of renal transplantation 4
- May resume 1 year post-transplant if catch-up growth does not occur 4
Turner Syndrome
- Weekly dosage up to 0.375 mg/kg divided into 3-7 injections per week 3