Is a testosterone level of 439 and free testosterone level of 15.6 within a therapeutic range for a female-to-male (FTM) patient after 2 months of 100 mg weekly testosterone (testosterone cypionate or testosterone enanthate) injections?

Testosterone Levels Assessment in FTM Transition

The testosterone level of 439 ng/dL and free testosterone of 15.6 pg/mL are both below the therapeutic target range for masculinizing hormone therapy, and the dose should be increased after 2 months of treatment. 1, 2

Target Testosterone Ranges for Gender-Affirming Therapy

While the provided guidelines focus on cisgender male hypogonadism treatment, the same physiologic principles apply to masculinizing hormone therapy:

• Target total testosterone should be in the mid-normal male range of 450-600 ng/dL 1, 2
• Free testosterone reference range for adult males is 66-309 pg/mL (2.5th-97.5th percentile), with young men aged 19-39 years having a range of 120-368 pg/mL 3
• The current total testosterone of 439 ng/dL falls just below the recommended target range of 450-600 ng/dL 1, 2
• The free testosterone of 15.6 pg/mL is substantially below even the 2.5th percentile (66 pg/mL) for healthy adult males 3

Dose Adjustment Strategy

Increase the weekly testosterone dose from 100 mg to 125-150 mg weekly:

• The current dose of 100 mg weekly is within the standard starting range of 50-100 mg weekly for testosterone enanthate or cypionate 1
• Since levels are subtherapeutic after 2 months (adequate time to reach steady state), a dose increase of 25-50% is appropriate 1, 2
• Weekly dosing provides more stable testosterone levels compared to biweekly administration, which should be maintained 1

Monitoring Timeline

• Recheck testosterone levels 2-3 months after this dose adjustment 1, 2, 4
• Measure levels midway between injections (3-4 days after injection if dosing weekly) 1, 2
• Draw morning testosterone levels between 8 AM and 10 AM for consistency 5
• Once stable therapeutic levels are achieved, monitor every 6-12 months 1, 2

Critical Considerations for This Patient

The discrepancy between total and free testosterone is notable:

• Free testosterone appears disproportionately low relative to total testosterone 3, 6
• This may suggest altered binding protein concentrations, though sex hormone-binding globulin (SHBG) levels were not provided 5, 7
• Consider measuring SHBG if the pattern persists after dose adjustment, as this can affect interpretation 5, 7, 6

Common Pitfalls to Avoid

• Do not maintain the current dose despite the patient being "close" to target range—subtherapeutic levels will not achieve full masculinization effects 1, 2
• Do not increase the dose too aggressively—a 25-50% increase is appropriate rather than doubling the dose 1
• Do not measure testosterone levels at random times—timing relative to injection and time of day matters for accurate assessment 5, 1, 2
• Do not forget to monitor hematocrit—injectable testosterone carries risk of erythrocytosis, particularly at higher doses 1, 2