Androgen Pharmacology

Introduction

  • Speaker: Dr. Jan

  • This video follows up on the subject of pharmacology related to male gonadal hormones, specifically hormone deficiencies and how they can be treated. This is important in understanding how hormones, particularly testosterone, play a role in male health.

Androgen Deficiency
Definition

  • Androgen deficiency primarily refers to a deficiency in testosterone, which is the main male sex hormone.

  • Testosterone also leads to the formation of another important hormone called dihydrotestosterone (DHT), which is critical for male physical characteristics. If testosterone is low, DHT levels can also drop, affecting various bodily functions.

Developmental Impact

Fetal Development

  • During the development of a male fetus, there is a significant increase in testosterone levels. This increase is crucial because it helps determine male physical features.

  • If there is no testosterone during fetal development, typically, the fetus will develop female characteristics. This is especially true if there is no Y chromosome, which is responsible for male traits.

  • A complete absence of testosterone in a fetus generally does not lead to developmental problems unless testosterone levels rise after birth.

Partial Deficiency Effects

  • If there is only a partial deficiency of testosterone during fetal development, it can result in noticeable changes, such as issues with sexual differentiation. This may lead to uncertainty in gender assignment at birth.

Pubertal Effects

  • Adequate testosterone levels during puberty are necessary for the development of male secondary sexual characteristics. If testosterone levels are low during this time, it can cause several problems:

    • Inhibition of puberty effects: This means that the physical changes that typically happen during puberty, such as growth of facial hair, deepening of the voice, and muscle development, may be delayed.

    • Extended bone growth: Low testosterone can prevent proper calcification of growth plates, leading to longer bone growth and resulting in taller stature but potentially impacting overall health.

    • Gynecomastia: This condition is characterized by the development of breast tissue in males. Low testosterone can lead to an imbalance in hormones that causes this development, particularly seen during puberty.

Post-Pubertal Effects

  • If testosterone levels decline after puberty, whether due to aging or other health reasons, the effects of this deficiency depend on how long the individual has lived with lower levels of testosterone.

  • Observable effects can include:

    • A decrease in sexual desire, or libido.

    • Loss of muscle mass, leading to a reduction in physical strength.

    • A slower decline of physical characteristics compared to loss of libido, meaning the body may retain some physical features of youth longer than sexual desire.

Treatment for Androgen Deficiency
Introduction of Exogenous Androgens

  • Treatment for those with androgen deficiency commonly involves providing testosterone to replace what the body is lacking. This can help restore normal hormone levels and alleviate associated symptoms.

Administration Methods

Oral Administration

  • When testosterone is taken as a pill, it is largely ineffective because it is significantly broken down by the liver. This process, called first-pass metabolism, results in almost no active testosterone reaching the bloodstream.

Modified Testosterone Compounds

  • To make testosterone more effective, there are two main methods that modify how it is administered:

    1. Esterification:

      • This involves chemically modifying testosterone so that it can be injected into the muscle. For example, testosterone enanthate is a common form that can release testosterone slowly over a week or two, helping maintain steady hormone levels.

    2. Alkylation:

      • This allows testosterone to be taken orally without being destroyed by the liver. However, this method carries a risk of liver damage, increasing the chance of serious health problems like liver cancer.

Comparisons of Administration Routes

  • Different methods of testosterone administration can create varying profiles of testosterone levels in the blood:

    • Testosterone injections result in a gradual increase in hormone levels, keeping them within a therapeutic range that is deemed healthy.

    • Patches and gels provide consistent dosing without large spikes in hormone levels, leading to fewer side effects. Patches provide a steady release for 24 hours, while gels can maintain more constant testosterone levels throughout the day.

Monitoring and Individualization of Treatment

  • During initial treatment, doctors closely monitor testosterone levels to make necessary adjustments. This ensures that the therapy effectively meets individual patient needs. Normalization of symptoms can happen at different rates:

    • Increased sexual desire and energy levels may improve within weeks to months.

    • Gain in muscle mass can take up to a year for significant changes to be seen.

    • Improvement in bone density may take as long as two years to fully realize the benefits of testosterone therapy.

Potential Side Effects of Androgen Administration
Common Effects

  • While benefits of testosterone therapy include improved libido, some side effects can occur that mimic natural testosterone fluctuations. Some common side effects are:

    • Acne, especially as testosterone levels rise, can be a significant issue for many individuals taking testosterone.

    • There are also risks of developing benign prostatic hyperplasia (BPH), which is an enlarged prostate, or cancer of the prostate, due to testosterone’s stimulating effects on prostate growth.

Risks of Alkylated Testosterone

  • Using alkylated forms of testosterone can present dangers, such as:

    • Hepatotoxicity: This highlights the potential damage to liver cells, increasing the risk of liver-related diseases.

    • Lower levels of HDL cholesterol, which is considered the good cholesterol, can lead to heart disease over time due to hormonal imbalances.

Performance-Enhancing Drugs (PEDs)
Use and Detection

  • In sports, some athletes misuse androgens to elevate their testosterone levels beyond what is natural to gain performance advantages. The FDA strongly advises against this practice due to the potential for serious health problems.

  • There has been a notable history of anabolic steroid misuse in sports, particularly during the late 20th century.

Detection Issues

  • Some athletes may switch to forms of testosterone that are less likely to be detected during drug testing, which can make it difficult for governing bodies to enforce fair play.

  • Newer androgens, such as tetrahydrogestrinone (THG), have been created specifically to evade detection by available drug tests, despite having no approved medical use.

Clinical Considerations

  • Studying the long-term effects of these drugs presents ethical challenges for researchers due to the risk of legal and societal repercussions for subjects involved in PED use. Nevertheless, some believe that high testosterone combined with exercise could lead to significantly increased muscle mass.

Treatment for Excess Androgens
Situations Requiring Reduction

  • There are instances when lowering testosterone levels is necessary, particularly in conditions like prostate cancer or when there is fluid retention that can arise due to high testosterone levels.

Medications for Reducing Androgens

Ketoconazole

  • This antifungal medication has the additional effect of inhibiting testosterone production, making it useful in cases where lowering testosterone is necessary.

Flutamide

  • Often used in conjunction with gonadotropin-releasing hormone (GnRH), flutamide works to counteract the effects of elevated testosterone, particularly in treating certain cancers.

5-alpha Reductase Inhibitors

  • Example: Finasteride

    • This medication is useful in conditions like benign prostatic hyperplasia (BPH) and male pattern baldness, as it works by preventing testosterone’s conversion into DHT, thereby helping to reduce unwanted effects from high androgens.

Erectile Dysfunction (ED) Treatments
Pharmacological Mechanism

  • An erection occurs when nitric oxide (NO) is released, leading to an increase in a molecule called cyclic GMP (cGMP). This molecule causes blood vessels to relax and expands, allowing for increased blood flow necessary for an erection.

PDE5 Inhibitors

  • Common medications for ED like Viagra and Cialis work to keep cGMP levels from breaking down. This allows for a more sustained erection by supporting blood flow:

    • However, safety precautions are necessary, as these medications can interact with other drugs, specifically those that affect and increase NO and cGMP, which may lead to dangerously low blood pressure.

Alternative Treatments

  • Other treatments to assist with erectile dysfunction include:

    • Guanylyl cyclase activators: These medications work by directly increasing cGMP levels in the body.

    • Arginase inhibitors: These aim to enhance the availability of the amino acid arginine, which is necessary for NO production and promotes better blood flow.

    • Rho-kinase inhibitors: These drugs help prevent blood vessels from constricting, thereby aiding in maintaining better erectile function.

Conclusion

  • This lecture summarized different approaches to treating androgen deficiencies, potential side effects, methods of addressing overactive androgen levels, and strategies for managing erectile dysfunction. Additionally, upcoming lectures will focus on female reproductive pharmacology and address issues related to female gonadal hormones.