Low Testosterone in Men
Background & Introduction
Video Lesson
Experts you'll learn from
Former President, ASRM
Professor, Urology
Weill Cornell Medicine
Vice President, ASRM
Vice Chair, Clinical Urology
Northwestern University Feinberg
Written Lesson
About This Course
Regardless of gender, hormones play crucial roles in overall well-being, influencing both physical and mental health. Hormonal imbalances affect people of all gender identities including cis and trans men and women, those who were assigned male or female at birth (AMAB, AFAB), and non-binary individuals.
While the primary emphasis of this course is on understanding low testosterone and its implications for men and AMAB individuals, we want to acknowledge that hormonal health is a nuanced topic that affects people across all gender identities. Hormonal health is a diverse field, and individuals experience unique challenges based on their own circumstances. If you don’t identify with concerns related to low testosterone, we encourage you to explore other resources that align more closely with your specific interests and needs.
For those seeking information on low testosterone, we aim to offer a comprehensive and informative exploration of this aspect of hormonal health. Whether you are navigating your own health journey or supporting someone else, our goal is to provide targeted insights into understanding and managing low testosterone.
What is Testosterone & Why Does It Matter
Testosterone is a hormone that is produced in all individuals, however it plays a central role in shaping overall health and vitality in men and people assigned male at birth. For this reason, it is often referred to as the male sex hormone. It is produced primarily in the testes although small amounts are also made in the adrenal glands and in the ovaries.
Testosterone is responsible for the development of secondary sexual characteristics associated with masculinity including facial and body hair development, muscle and bone growth, laryngeal (voice box) and vocal cord development leading to deepening of the voice, fat distribution, and physical strength. But testosterone is not just about physical features; it's a key player in various aspects of our well-being from libido and sexual function to metabolic processes and mood. A deficiency of testosterone can lead to a range of issues including impaired sugar metabolism and weight gain, bone degeneration, anxiety, depression, sexual performance issues, cardiovascular disease, and infertility.
Normal Endocrine Function & How Things Can Get Disrupted
Normal Functioning Endocrine System
Testosterone is a hormone, and for it to function properly, the endocrine system needs to work properly. Before we dive into the nuances of testosterone and how Low T can come about, let’s talk about what the endocrine system looks like when it functions properly.
Let’s start by defining a few of the terms and processes of the endocrine system which will come in handy as you make your way through this course.
For the body to function, cells have to communicate with one another. The endocrine system is a type of communication system whereby cells communicate through chemical messengers known as hormones. For instance, when your brain produces the hormone adrenaline, it prepares your body for action.
Hormones are transported by the blood from the cells that produce them to the rest of the body. A cell picks up a hormonal message when the hormone binds to their receptor, after which the cell initiates processes that lead to an action. Hormone action is very specific in the body because hormones only act on those cells (areas of the body) that have receptors specific for that hormone’s action. That action may be to start (positive action) or to stop (negative action) a process in the specific region or tissue of the body.
When any step in this process (e.g. cells don’t produce hormones; hormones don’t bind to the receptor; receptors are bound to another substance) is disrupted, the body is unable to complete the task.
How Testosterone Fits Into The Endocrine System
The brain sends a hormone called LH (luteinizing hormone), a gonadotropin, to the testes, which utilize that signal to produce testosterone. This testosterone circulates throughout the body, influencing muscle formation, mood, and sperm production. Back in the brain, testosterone functions to indicate the necessary levels of gonadotropin needed to restart the process.
How Things Can Go Wrong
There are different types of hypogonadism that typically reflect a breakdown either in the brain or in the testes. While “primary” hypogonadism tends to reflect an issue in the testes, other forms (secondary, central, tertiary) tend to reflect “upstream” challenges in the brain. In the next section, we’ll look at each of these forms of hypogonadism individually.
Testosterone plays a crucial role in the body's communication system between the brain and the testes, known as the hypothalamic-pituitary-gonadal axis (HPG axis). Here's how it works:
In the brain, a gland called the hypothalamus releases a hormone called gonadotropin-releasing hormone (GnRH). This hormone tells another brain structure called the pituitary gland to release two hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Together, LH and FSH are called gonadotropins.
Gonadotropins are hormones that help control the reproductive system. They stimulate the sex glands (like the testes in males and ovaries in females) to produce sex hormones and support processes like sperm and egg development. In males, gonadotropins stimulate the testes to produce testosterone and sperm cells, a process called spermatogenesis.
LH specifically boosts the production of testosterone in cells called Leydig cells within the testes, increasing its concentration of testosterone in the testes to more than 40 times that found in circulation. In this high-testosterone environment, FSH stimulates spermatogenesis.
Testosterone also plays a role in regulating the HPG axis through negative feedback. When there's enough testosterone in the system, it signals the brain to reduce the production of GnRH, FSH, and LH, maintaining a balance of hormones.
Clarifying Terminology
You might be familiar with the term "andropause," which is often employed to characterize a phase in a man's life comparable to menopause in women. This period, sometimes referred to as male menopause, is characterized by various physiological and hormonal changes that typically occur as a man ages and can impact a man's well-being. As in menopause, this phase involves a gradual decline in hormone levels, particularly testosterone, leading to a range of symptoms that can affect both physical and emotional aspects of life.
In addition to "andropause," other terms are employed to describe the condition of low testosterone, including low testosterone, low T, and testosterone deficiency syndrome (TDS). Clinically, these are all referred to as male hypogonadism, a condition in which the male gonads, or testes, produce inadequate amounts of the primary sex hormone, testosterone.