What are the side effects of growth hormone therapy?

Growth Hormone Therapy Side Effects

Growth hormone therapy is generally safe when properly dosed and monitored, but requires vigilance for several key adverse effects: fluid retention/edema (most common), glucose intolerance/diabetes, and endocrine axis disruption (thyroid and adrenal function). 1

Common and Dose-Dependent Side Effects

Fluid Retention and Edema

• Peripheral edema occurs in approximately 15% of treated patients (vs 3.6% with placebo), making it the most frequent side effect 1
• Mechanism: GH increases distal tubular sodium reabsorption, causing ~1 kg extracellular fluid gain
• Management: Reduce dose immediately if edema develops - this side effect is directly dose-dependent 1

Metabolic Effects on Glucose

GH therapy worsens glucose tolerance in 13% of patients and causes new-onset diabetes in 4% 1

• GH decreases insulin sensitivity through direct metabolic effects
• Risk factors for glucose complications:
  • Age >60 years
  • Pre-existing glucose intolerance
  • Higher body mass index
  • Adult-onset GH deficiency 2

Critical action: Monitor diabetic patients closely and adjust antidiabetic medications as needed 1

Endocrine Axis Disruption

GH replacement lowers free T4 and cortisol levels, potentially unmasking previously hidden deficiencies 1

Mandatory monitoring protocol:

• Check thyroid function during treatment; adjust levothyroxine doses as needed
• Reassess hypothalamic-pituitary-adrenal axis during therapy
• Institute glucocorticoid replacement if central hypoadrenalism emerges 1

Serious but Rare Complications

Musculoskeletal Issues

• Arthralgia (joint pain) - relatively common 3
• Progression of pre-existing scoliosis - monitor in at-risk patients 3, 4
• Slipped capital femoral epiphysis - particularly in adolescents with GH deficiency, especially post-leukemia treatment 4

Neurological

• Benign intracranial hypertension: Only 2 cases reported in adults (more common in children) 1
• Retinopathy: Extremely rare - only 2 documented adult cases, both resolved after GH withdrawal 1

Other Rare Effects

• Gynecomastia (reported only in elderly receiving high doses) 1
• Injection site reactions and transient fever 3

Cancer Risk: The Critical Concern

GH therapy is absolutely contraindicated in patients with active malignancy 1

Evidence on Cancer Risk:

• No increased risk of tumor recurrence or new malignancies has been demonstrated in multiple large epidemiological studies 1
• No increase in recurrence rates of intracranial or extracranial tumors in adults with GH deficiency 1
• Despite theoretical concerns about IGF-I promoting cancer, long-term safety data are reassuring 5

Clinical approach:

• Avoid GH in active malignancy due to theoretical proliferative effects
• After cancer remission: GH can be considered with close monitoring and appropriate waiting period
• Individual risk/benefit analysis required for cancer survivors 6, 5

Risk Factors for Developing Side Effects

Patients most likely to experience side effects: 2

• Age >60 years
• Peak GH response >1 mU/L on testing
• Adult-onset (vs childhood-onset) GH deficiency
• Higher body weight and BMI
• Larger increment in IGF-I levels during treatment

Mitigation Strategy

Start low, go slow, and individualize dosing based on clinical response, side effects, and IGF-I levels 1

Key dosing considerations:

• Lower starting doses for: patients >60 years, those with glucose intolerance, those on low prior daily GH doses
• Higher doses may be needed for: younger adults, women on oral estrogen, those with panhypopituitarism 6
• Women on oral estrogen require higher doses due to hepatic IGF-I suppression 1

Common pitfall: Using weight-based dosing rather than individualized titration increases side effect risk. Always adjust based on clinical response and IGF-I monitoring 1