How do men make Testosterone?

February 13, 2024

Understanding Testosterone Production in Men: A Comprehensive Guide

Testosterone is an important hormone in a man’s body, and plays a vital role in several physiological processes, including the development of reproductive tissues, building lean muscle mass, the improvement of bone density, and the distribution of body fat to name a few. Understanding how the body produces testosterone is essential for comprehending its significance and potential implications for men's health.

The process of how testosterone is produces primarily occurs in the testes, specifically within specialized cells called Leydig cells. These cells are found in the interstitial tissue surrounding the seminiferous tubules. This is where spermatogenesis (sperm production) takes place. Testosterone production is regulated by a complex interplay of hormonal signals originating from the hypothalamus and the pituitary gland. This is often referred to as the HPG-Axis, or the hypothalamic-pituitary-gonadal axis.

It all starts with the hypothalamus, the area of the brain responsible for regulating various bodily functions. One of these important functions is the regulation and secretion of hormones. The hypothalamus will detect a depletion of testosterone in the blood stream and respond by producing gonadotropin-releasing hormone (GnRH), which travels to the nearby pituitary gland. In response to GnRH being secreted by the hypothalamus, the pituitary gland releases two key hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH travels via the blood stream to the testes and stimulates the Leydig cells to produce testosterone. Once the LH interacts with the receptor sites in the Leydig cells, they begin the process of testosterone synthesis.

This process involves multiple enzymatic reactions which will then convert cholesterol, a precursor molecule, into testosterone. The enzyme responsible for starting this conversion is called cholesterol desmolase, which is also known as cytochrome P450 side-chain cleavage enzyme (CYP11A1), is synthesized within the endoplasmic reticulum of steroidogenic cells, including Leydig cells in the testes. This enzyme is encoded by the CYP11A1 gene. After synthesis, cholesterol desmolase is transported to the mitochondria, where it plays a vital role in the conversion of cholesterol to pregnenolone, the precursor molecule in the biosynthesis of steroid hormones, including testosterone.

Once cholesterol is converted into testosterone, the hormone is released into the bloodstream, where it circulates throughout the body, exerting its effects on various tissues and organs. Testosterone production is a tightly regulated process, with levels fluctuating in response to several factors unique to each individual, including age, physical activity, stress, and overall health and genetics.

The body’s regulation of testosterone production also involves a negative feedback mechanism to maintain hormonal balance. When testosterone levels in the blood reach a certain threshold, they’ll signal the hypothalamus and pituitary gland to decrease the secretion of GnRH, LH, and FSH. This feedback loop helps prevent excessive testosterone production, ensuring hormonal homeostasis. Interestingly, men who take steroids or who are on TRT may experience testicular atrophy as they shut down this HPG-Axis.

Several factors can influence testosterone production in men,including age, genetics, lifestyle, medications, and underlying medical conditions. Testosterone levels normally peak during adolescence and early adulthood, which will promote the development of secondary sexual characteristics and supporting reproductive function. Characteristics like the Growth of facial and body hair, deepening of the voice, broadening of the shoulders and increasing muscle mass,developing an Adam’s apple (enlargement of the larynx), growth of facial bones, leading to a more angular jawline and other masculine facial features and more.  However, as men age, testosterone production gradually declines, leading to various age-related changes, such as reduced muscle mass, decreased bone density, and alterations in mood and cognition. This often becomes noticeable in men in their 40’s which is why testosterone therapy is becoming so popular.

In addition to the age-related decline of testosterone levels,certain medical conditions, such as hypogonadism (a condition characterized by insufficient testosterone production), may also affect testosterone levels. Hypogonadism can be caused by congenital abnormalities, injury to the testicles, or brain disorders which can affect the hypothalamus or pituitary gland. Treating hypogonadism can often involve testosterone replacement therapy, or TRT to restore hormonal balance and alleviate symptoms of Low T.

Maintaining optimal testosterone levels is essential for the overall health and well-being in men. While testosterone production naturally declines with age, adopting a healthy lifestyle can help support hormone production andfunction. Regular exercise, a balanced diet, adequate sleep, and stress management are all important factors in promoting hormonal health. Testosterone production in men is a complex process regulated by the interplay of various hormones and physiological factors. Understanding how the body synthesizes testosterone is crucial for comprehending its role in male physiology and addressing the potential issues related to Low T. By promoting hormonal optimization through lifestyle modifications and appropriate medical interventions like testosterone replacement therapy, men can optimize their overall well-being and qualityof life.


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Blood Work Request Form

This subsequent lab panel is necessary for males undergoing Testosterone Replacement Therapy (TRT) through NovaGenix Health and Wellness. It allows physicians to assess the patient's response to prescribed medications, covering sex hormone levels, thyroid function, adrenal health, hematocrit, and liver and kidney function. The panel includes tests such as:

  • Complete Blood Count
  • Comprehensive Metabolic Panel
  • Testosterone (Free and Total)
  • Estradiol Sensitive
  • Thyroid Stimulating Hormone
  • Prostate Specific Antigen

Each test serves a specific purpose in monitoring overall health and treatment effectiveness. When required, Dr Mackey may require LH and FSH (Luteinizing hormone, follicle stimulating hormone) SHBG (Sex hormone binding globulin) or any other tests which may be important for your health and optimizing your hormones.

The Comprehensive Hormone and Wellness Panel for Women offers a foundational assessment of sex hormones, thyroid function, adrenal health, metabolic activity, and overall well-being. This panel serves as a diagnostic tool for identifying testosterone and estrogen deficiencies, assessing health risks, and detecting potential thyroid issues before considering hormone replacement therapy. Additionally, it includes insights into hematocrit (red blood cell volume), as well as liver and kidney function. The panel encompasses various tests such as:

  • Complete Blood Count (CBC)
  • Complete Metabolic Panel
  • Testosterone (free and total)
  • Estradiol
  • Thyroid Stimulating Hormone (TSH)
  • Progesterone

When indicated, Dr. Mackey may require additional tests such as Follicle Stimulating Hormone (FSH), and IGF-1 and Cortisol.

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