From the Guidelines
To assess excessive testosterone injection, total testosterone should be measured, as it is the primary measurement used to monitor testosterone replacement therapy. When evaluating testosterone levels, it is essential to consider the timing of the measurement, as levels can fluctuate depending on the type of testosterone preparation used [ 1 ]. For patients receiving testosterone injections, levels should be measured midway between injections, targeting a mid-normal value (500-600 ng/dL) [ 1 ]. While free testosterone can provide additional information about bioavailable hormone levels, total testosterone is the standard initial measurement for dose adjustment [ 1 ]. Key points to consider when measuring testosterone levels include:
- The target range for total testosterone in those on therapy is typically 400-700 ng/dL [ 1 ]
- Blood should be drawn at the midpoint between injections to get the most accurate assessment [ 1 ]
- If total testosterone levels are significantly above the normal range, this indicates the dose is too high and should be reduced to avoid potential side effects [ 1 ]
- Regular monitoring every 3-6 months is recommended to ensure levels remain appropriate [ 1 ]. It is crucial to prioritize the measurement of total testosterone to ensure safe and effective testosterone replacement therapy, as excessive levels can lead to severe side effects, including polycythemia, mood swings, acne, or cardiovascular issues [ 1 ].
From the FDA Drug Label
Testosterone in plasma is 98 percent bound to a specific testosterone-estradiol binding globulin, and about 2 percent is free. Generally, the amount of this sex-hormone binding globulin in the plasma will determine the distribution of testosterone between free and bound forms, and the free testosterone concentration will determine its half-life
To assess excessive testosterone injection, free testosterone should be measured, as it is the active form of testosterone and determines its half-life.
- The free testosterone concentration is the most relevant measure, as it is the biologically active form of testosterone.
- Measuring total testosterone may not accurately reflect the amount of active testosterone, as it includes both bound and free forms. 2
From the Research
Assessing Excessive Testosterone Injection
To determine whether total or free testosterone should be measured to assess excessive testosterone injection, several studies provide relevant information:
- Total testosterone levels are often used as a primary index of androgen status, and most clinical laboratories employ automated analyzers to quantify total plasma testosterone in men 3.
- However, when concentrations of plasma testosterone are found to be around the lower limit of normal, some measure of bioactive testosterone, such as free or bioavailable testosterone, should be sought 3.
- Free testosterone levels can be measured or calculated using mathematical expressions, but this may be laborious and time-consuming, making it unsuited to routine clinical laboratories 3.
- Studies have shown that subcutaneous injection of testosterone can effectively achieve serum total testosterone levels within the normal male range, with some patients preferring this method over intramuscular injection 4, 5.
- The measurement of free testosterone may be more relevant in certain cases, such as when assessing the effects of testosterone replacement therapy on hypogonadal men, as it can provide a more accurate estimate of bioactive testosterone 6, 7.
Key Findings
- Total testosterone levels can be used to assess androgen status, but free testosterone levels may be more relevant in certain cases 3, 6, 7.
- Subcutaneous injection of testosterone can effectively achieve serum total testosterone levels within the normal male range 4, 5.
- Free testosterone levels can be measured or calculated, but this may be laborious and time-consuming 3.
- The choice of measurement (total or free testosterone) may depend on the specific clinical context and the goals of the assessment 3, 6, 7.