How much does testosterone typically decline each year after age 30?

After age 30-35, total testosterone typically declines by about 1% per year, while free testosterone may decrease by 2-3% annually. However, this is a generalization, and some individuals retain high levels much later in life.

When is Testosterone Replacement Therapy (TRT) most justified?

The most compelling case for TRT is primary hypogonadism, where the testes don't respond to pituitary signals (high LH/FSH) but testosterone levels are low. Secondary hypogonadism, with low LH/FSH, may indicate lifestyle issues like poor sleep or high stress that should be addressed first.

What is a common starting dose for TRT?

A common and generally safe starting dose for TRT is around 100-120 mg per week, often adjusted based on individual response, SHBG levels, and symptom relief. Some physicians start lower, between 80-120 mg weekly.

Is it better to inject testosterone once a week or more frequently?

Injecting more frequently, such as twice a week or even daily, is generally preferred for maintaining more stable hormone concentrations and potentially reducing side effects like estrogen spikes and hematopoesis.

What are the pros and cons of nasal testosterone formulations?

Nasal formulations like NasalTesto offer rapid absorption and require frequent dosing (TID). They are associated with reduced hematopoesis and can be used by women. However, they may have a short half-life, requiring consistent adherence.

What's the difference between subcutaneous and intramuscular testosterone injections?

Subcutaneous injections into fat tissue may provide a slightly longer, more sustained release compared to intramuscular injections, which are absorbed more quickly due to higher blood flow. For frequent dosing (e.g., every other day), the difference may be less significant.

Why is frequent testosterone dosing thought to reduce side effects like gynecomastia?

Frequent dosing helps avoid the large spikes in testosterone associated with once-weekly injections. These spikes can lead to supraphysiological conversion into estrogen (causing gynecomastia) and DHT, as well as increased sympathetic nervous system activation.

Key Moments

Testosterone replacement therapy: compelling use cases, side effects, and optimal dosing schedules

Peter Attia MD

Science & Technology3 min read22 min video

Jun 23, 2024|695,215 views|7,998|1,316

Peter Attia MD Dr. Peter Attia Early Medical The Drive Podcast The Drive Longevity Zone 2

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Key Moments

TL;DR

TRT offers benefits for hypogonadism, but optimal dosing and frequency are key to managing side effects and maximizing results.

Key Insights

Testosterone levels naturally decline with age, but consulting a doctor is crucial before considering TRT.

Primary hypogonadism (testicular failure despite adequate signaling) is the most compelling reason for TRT.

Dosing frequency significantly impacts hormone stability and can mitigate side effects like gynecomastia.

Subcutaneous injections may offer a more sustained release compared to intramuscular injections.

FDA-approved formulations can be preferable to compounded versions, offering standardized dosing and quality.

Personalized TRT regimens are essential, considering individual responses, lifestyle, and goals.

NATURAL DECLINE VS. CONSIDERATION FOR TRT

Testosterone levels naturally decrease with age, typically starting around 30-35, with an estimated 1% drop in total testosterone and 2-3% in free testosterone per year. However, this decline is gradual and can vary significantly among individuals; some older men retain high testosterone levels. It's crucial not to assume a diagnosis based on age alone. Consulting a healthcare professional is essential to assess individual levels, understand contributing factors like lifestyle, sleep, and nutrient intake, and determine if TRT is appropriate rather than solely relying on age-related expectations.

COMPELLING USE CASES FOR TRT

The most medically justified reason for TRT is primary hypogonadism, where the testes fail to respond adequately to hormonal signals (high LH and FSH) despite sufficient signaling from the pituitary gland. This condition can sometimes be linked to structural or functional testicular abnormalities, such as varicoceles, which should be investigated. In contrast, secondary hypogonadism, characterized by low testosterone with low LH and FSH, often points to issues like poor sleep or elevated cortisol levels, which may be addressed through lifestyle changes rather than TRT.

OPTIMAL DOSING STRATEGIES AND FREQUENCY

While fixed dosing is common, optimal TRT likely involves a dynamic approach. A reasonable starting point for exogenous testosterone, such as testosterone cypionate, ranges from 80-120 mg per week, with adjustments based on individual response and symptom relief. However, dosing frequency is critical for stable hormone levels. Splitting doses from once weekly to twice weekly, or even daily, can significantly reduce hormonal spikes, minimize conversion to estrogen and DHT, and lower the risk of side effects like gynecomastia and sleep disturbances.

IMPACT OF INJECTION FREQUENCY ON SIDE EFFECTS

Infrequent injections (e.g., once weekly) can lead to supraphysiological testosterone peaks, concurrently increasing estrogen and DHT conversion and potentially causing sympathetic nervous system activation, sleep disruption, and increased red blood cell production (hematopoiesis). More frequent dosing regimens, such as twice weekly or daily, more closely mimic natural hormonal rhythms. This approach can reduce aromatization, lower DHT conversion, and allow individuals to potentially discontinue aromatase inhibitors, thereby improving overall hormonal balance and reducing side effect burden.

SUBQ VS. INTRAMUSCULAR INJECTIONS

The method of testosterone administration also plays a role in its pharmacokinetic profile. Subcutaneous (subQ) injections, particularly with less frequent dosing, may provide a more sustained release of testosterone compared to intramuscular (IM) injections, which are absorbed more rapidly due to higher blood flow. While definitive data is limited, the perception is that subQ may lead to more stable total testosterone levels over time. For individuals undergoing frequent dosing schedules, the difference between subQ and IM may become less significant.

FDA-APPROVED FORMULATIONS AND PERSONALIZED APPROACHES

Opting for FDA-approved formulations, like those available in pre-loaded pens such as Zast (testosterone enanthate), can offer convenience and standardized dosing, especially for individuals hesitant about self-injection. However, these may come at a higher cost and offer less flexibility in dose titration compared to injectable vials of testosterone cypionate. Ultimately, the most effective TRT regimen is personalized, considering individual metabolic responses, adherence to protocol, lifestyle factors, and the pursuit of stable hormone levels with a minimized side effect profile.

Mentioned in This Episode

●Supplements

●Products

●Tools

●Concepts

TRT Dosing and Administration Best Practices

Practical takeaways from this episode

Do This

Consider more frequent injections (e.g., twice weekly or daily) for more stable hormone levels and potentially fewer side effects.

Subcutaneous injection may offer a more sustained release compared to intramuscular, especially for less frequent dosing.

Evaluate SHBG levels to understand testosterone binding and potential for low free T, even with normal total T.

For those seeking optimization, aim for a dosing regimen that minimizes large fluctuations and spikes.

If using pre-loaded pens like Zestica, consider splitting the dose to twice weekly for better stability, even if the FDA protocol is once weekly.

Avoid This

Do not rely solely on total testosterone levels; consider free testosterone and SHBG.

Avoid infrequent injections (e.g., once every two weeks) which can lead to significant hormone fluctuations and side effects.

Do not underestimate the impact of lifestyle factors (sleep, stress) on testosterone levels.

Avoid self-treating based on perceived low levels without proper medical assessment and blood work.

Be cautious of compounding pharmacies and favor FDA-approved formulations when possible, though cost and customization may be factors.

Common Questions

Normal testosterone levels can vary, but generally, total testosterone levels are often cited in ranges like 300-1000 ng/dL. However, the interpretation is complex as free testosterone and age are crucial factors, and lab ranges can be broad.

Topics

Androgens Injection Frequency Subcutaneous Vs Intramuscular

Mentioned in this video

productZestica

A brand name for an auto-injector pen containing testosterone enanthate, designed for ease of use but with limited dosing flexibility.

conceptFree Testosterone

Refers to the unbound, biologically active form of testosterone, which is difficult to measure directly and is often estimated.

drugTestosterone Cypionate

A commonly prescribed ester of testosterone for TRT, with a long half-life (around 10 days) that influences injection frequency.

drugTestosterone Enanthate

An ester of testosterone with a half-life typically shorter than cypionate, often used in TRT and available in pre-loaded pens like Zestica.

conceptTotal Testosterone

The overall amount of testosterone in the blood, including bound and unbound forms. Used to estimate free testosterone levels.

drugAromatase Inhibitor

Medications used to reduce the conversion of testosterone to estrogen, sometimes prescribed alongside TRT to manage side effects like gynecomastia.

conceptAndrogen receptors

Receptors in the body that bind with androgens like testosterone, mediating their effects. The number of these receptors influences how much testosterone is needed.

conceptPrimary Hypogonadism

A condition characterized by the testes not responding adequately to gonadotropin signaling (LH and FSH), resulting in low testosterone despite normal or high pituitary signals.