When to check testosterone level in patients on intramuscular testosterone injections and topical testosterone therapy?

From the Guidelines

Testosterone levels should be checked 2 to 3 months after treatment initiation with intramuscular testosterone injections or topical testosterone therapy, and/or after any dose change, to ensure that normal serum testosterone concentrations are being achieved 1. When monitoring testosterone levels in patients on intramuscular testosterone injections, it is recommended to measure levels midway between injections, targeting a mid-normal value (500-600 ng/dL) 1. For patients receiving transdermal preparations, levels can be measured at any time, with the understanding that peak values occur 6 to 8 hours after application of the patch, and that testosterone concentrations can vary substantially with gel use, although not in a predictable way 1. The goal of testosterone therapy is to maintain total testosterone levels between 300 to 800 ng/dL for most adult men, with the aim of alleviating symptoms of hypogonadism and improving quality of life 1. Regular monitoring every 6 to 12 months is typically sufficient once stable levels are confirmed on a given dose 1, 2. It is essential to note that individual responses to testosterone therapy vary, and adjusting the testing schedule based on the doctor's recommendations is crucial 1. Additionally, testing should include not just testosterone but also other parameters to monitor for potential side effects, such as complete blood count, liver function, lipid panel, and PSA (in men over 40) 1. In terms of follow-up, clinicians should measure an initial follow-up total testosterone level after an appropriate interval to ensure that target testosterone levels have been achieved, and discuss the cessation of testosterone therapy if patients achieve target testosterone levels but do not feel that they have sufficient improvement in their symptoms 2.

Key points to consider when checking testosterone levels in patients on intramuscular testosterone injections and topical testosterone therapy include:

• Measuring levels 2 to 3 months after treatment initiation or after any dose change
• Targeting a mid-normal value (500-600 ng/dL) for patients on intramuscular injections
• Measuring levels at any time for patients on transdermal preparations, with consideration of peak values and variability
• Maintaining total testosterone levels between 300 to 800 ng/dL for most adult men
• Regular monitoring every 6 to 12 months once stable levels are confirmed
• Adjusting the testing schedule based on individual responses to therapy and doctor's recommendations
• Including other parameters in testing to monitor for potential side effects.

From the FDA Drug Label

CLINICAL PHARMACOLOGY During exogenous administration of androgens, endogenous testosterone release is inhibited through feedback inhibition of pituitary luteinizing hormone (LH).

PHARMACOKINETICS Testosterone esters in oil injected intramuscularly are absorbed slowly from the lipid phase; thus, testosterone cypionate can be given at intervals of two to four weeks

PHARMACOKINETICS Testosterone esters are less polar than free testosterone. Testosterone esters in oil injected intramuscularly are absorbed slowly from the lipid phase; thus testosterone enanthate can be given at intervals of two to four weeks.

The FDA drug label does not answer the question.

From the Research

Monitoring Testosterone Levels

• Patients on intramuscular testosterone injections and topical testosterone therapy should be monitored to ensure testosterone levels rise appropriately and clinical improvement occurs 3, 4.
• Testosterone levels should be checked after initiation of therapy to assess the response to treatment and adjust the dose as needed 4, 5.
• For patients on transdermal testosterone gel, serum testosterone levels can be measured at peak (2 hours after application) and trough (23 hours after application) to finely tailor the treatment 4.
• For patients on intramuscular testosterone injections, hormone levels can be measured at regular intervals (e.g., days 1-7 and day 14 after administration) to assess the response to treatment 5.

Timing of Testosterone Level Checks

• Testosterone levels should be checked within 1-3 months after initiating therapy to assess the response to treatment 6, 4.
• Subsequent checks can be performed at regular intervals (e.g., every 3-6 months) to monitor the stability of testosterone levels and adjust the dose as needed 6, 4.
• Patients on intramuscular testosterone injections may require more frequent monitoring due to the fluctuating nature of testosterone levels after injection 5.

Factors to Consider

• Clinical symptoms and signs of hypogonadism, such as loss of body hair, sexual dysfunction, and decreased libido, should be taken into account when monitoring testosterone levels 3, 7.
• Patient age, weight, and baseline testosterone levels can influence the starting dose and subsequent adjustments of testosterone therapy 7, 6.
• Potential risks and benefits of testosterone therapy, including cardiovascular complications and changes in prostate-specific antigen levels, should be considered when monitoring testosterone levels 3, 7.