Testosterone Injection Regimen for Confirmed Low Testosterone
For patients with confirmed low testosterone levels, the recommended treatment regimen using testosterone injections is intramuscular testosterone enanthate or cypionate administered every 2-3 weeks, with target mid-normal testosterone levels (500-600 ng/dL) measured midway between injections. 1
Diagnosis Confirmation
- Diagnosis requires both persistent specific symptoms and confirmed testosterone deficiency through biochemical testing 1
- Morning serum total testosterone measurements should be repeated to confirm low levels due to variability in assays 1
- Distinguish between primary (testicular) and secondary (pituitary-hypothalamic) hypogonadism by measuring LH and FSH levels 1
Injection Protocol
- Intramuscular testosterone injections (cypionate or enanthate) are administered every 2-3 weeks 1
- Peak serum levels occur 2-5 days after injection, with return to baseline usually observed 10-14 days after injection 1
- For patients receiving testosterone injections, levels should be measured midway between injections, targeting a mid-normal value (500-600 ng/dL) 1
- Subcutaneous administration is an emerging alternative that provides comparable pharmacokinetics to intramuscular injections with less pain and easier self-administration 2, 3
Monitoring Schedule
- Testosterone levels should be tested 2-3 months after treatment initiation and/or after any dose change 1
- Once stable levels are confirmed on a given dose, monitoring every 6-12 months is typically sufficient 1
- Patients receiving testosterone replacement therapy should be re-evaluated 3 months after testosterone initiation and at least annually thereafter 4
Expected Benefits
- Improved sexual function and libido 1
- Small improvements in quality of life 5, 6
- Potential improvements in fasting plasma glucose, insulin resistance, and lipid profiles 1
- Modest improvements in vitality and fatigue 5
Potential Side Effects and Risks
- Erythrocytosis is a potential risk with a higher incidence compared to transdermal preparations 1
- Fluid retention, benign prostatic hyperplasia, sleep apnea, gynecomastia, acne or oily skin, and testicular atrophy are potential side effects 1
- No significant increase in cardiovascular or cerebrovascular events based on current evidence 6
- No evidence of increased risk for serious adverse events 5
Contraindications
- Testosterone replacement should be avoided in patients with prostate or breast cancer, hyperviscosity, erythrocytosis, untreated obstructive sleep apnea, or severe heart failure 4
- Not FDA-approved for age-related hypogonadism 7
Alternative Formulations
- Transdermal testosterone preparations (gel, patch) provide more stable day-to-day testosterone levels compared to injections 1
- Patient preferences vary, with some preferring injections due to lower cost 5, while others prefer topical gel for convenience and ease of use 5
- Subcutaneous administration is gaining popularity as it allows for easier self-administration with comparable efficacy to intramuscular injections 2, 8, 3