Testosterone - What It Does, How It Changes, and What You Can Actually Do About It

Testosterone

A hormone that controls male sexual characteristics and body functions. It is produced mainly in the testicles but also in small amounts by the adrenal glands (small glands that sit on top of the kidneys).

Steroid Hormone

A type of hormone made from cholesterol that travels through the bloodstream delivering chemical messages to the body.

Androgens

A group of hormones that cause male characteristics to develop. Testosterone is the most important androgen.

Leydig Cells

Special cells in the testicles that produce testosterone. These cells produce about 95 percent of all testosterone in men's bodies.

Hypogonadism (Low Testosterone)

A medical condition where the body does not produce enough testosterone. It causes specific symptoms and is confirmed by blood tests.

Andropause

The gradual decline of testosterone as men age. Unlike female menopause which happens suddenly, male andropause is slow and spread over decades.

Aromatase

An enzyme (chemical) in fat tissue that converts testosterone into estrogen. More body fat means more aromatase and less testosterone.

TRT (Testosterone Replacement Therapy)

Medical treatment that provides testosterone to men with confirmed low levels. It is prescribed by doctors and requires monitoring.

The Basics

Testosterone is a hormone made from cholesterol and produced primarily in the testicles (about 95 percent of your testosterone comes from here). The adrenal glands, which sit on top of your kidneys, produce the remaining 5 percent.

Interestingly, women also produce testosterone in their ovaries and adrenal glands, just at much lower levels (about 5 to 10 percent of what men produce). Testosterone is important for female health too.

What Testosterone Does Before Birth and During Puberty

Before you were born, testosterone drove the development of male genitalia and reproductive organs.

During puberty, testosterone triggered the development of male characteristics. It deepened your voice, grew body and facial hair, enlarged your penis and testicles, built muscle, grew bones, and started sperm production.

What Testosterone Does in Adult Life

In adult men, testosterone maintains muscle mass and strength, keeps bones dense, produces red blood cells, maintains sperm production, drives sex drive (libido), provides energy, stabilizes mood, and supports cognitive function.

Testosterone also affects where your body stores fat. It favors muscle over fat storage. When testosterone falls, fat tends to accumulate, particularly around the abdomen. This is why men with low testosterone often gain belly fat.

How Testosterone Is Measured

Testosterone levels are measured in blood tests. There are two important measurements.

Total testosterone is all testosterone in the blood, both the testosterone attached to proteins and the free testosterone floating around. Free testosterone is only the unbound portion that is actually active and available for your cells to use. Free testosterone is what actually does the work.

Normal total testosterone in adult men ranges from 10 to 30 nmol/L (using metric measurements). When doctors say you have low testosterone (hypogonadism), they typically mean total testosterone is below 8 to 10 nmol/L, along with symptoms.

Important Testing Information

Testosterone levels change throughout the day. They peak in the early morning (around 8 am) and fall as the day goes on. Blood tests should always be taken in the morning for accurate results.

A single low reading is not enough for diagnosis. Doctors typically require two separate morning blood tests showing low testosterone before confirming low testosterone as a diagnosis.

The Natural Decline

Testosterone levels peak in the late teens and early twenties. After that, testosterone gradually begins to decline. After age 30, total testosterone falls by approximately 1 to 2 percent per year on average.

This slow, gradual decline over decades is fundamentally different from female menopause, which happens suddenly over a few years. Many men maintain normal testosterone levels well into their 70s and beyond. Some men never develop low testosterone at all.

Not Inevitable or Universal

The decline of testosterone with age is normal but not inevitable. It is not a disease. It does not automatically require treatment. The gradual decrease is part of normal aging, similar to how muscle mass or bone density gradually decline with age if you do not exercise.

What Low Testosterone Feels Like

• Reduced sex drive is often the first symptom. You simply feel less interested in sex.

• Erectile dysfunction (difficulty achieving or maintaining erections) is common, though low testosterone alone rarely causes ED without other problems.

• Reduced morning erections. Spontaneous erections in the morning are testosterone-dependent. Their absence can be a useful indicator.

• Progressive muscle loss and weakness that is hard to counter with exercise.

• Increasing body fat, particularly belly fat.

• Fatigue and reduced energy. A general sense of feeling less vital.

• Low mood, depression, and irritability.

• Reduced body and facial hair.

• Reduced bone density (this increases fracture risk over time).

• Mild anemia (low red blood cells).

• Reduced testicular size.

• Infertility from reduced sperm production.

What Actually Works

Resistance training is the most consistently effective natural testosterone booster. Compound exercises like squats, deadlifts, and bench press involving large muscle groups produce the greatest testosterone response. Aim for 3 to 4 strength training sessions per week.

Losing excess body fat, especially belly fat, significantly raises testosterone. Studies show that losing 10 to 15 percent of body weight can increase testosterone by 15 to 50 percent. This is one of the most effective interventions.

Prioritizing sleep is crucial. Aim for 7 to 9 hours per night in a dark, cool room. Sleep quality matters as much as quantity. If you have sleep apnea (a common condition in overweight men), treating it can significantly raise testosterone.

Managing chronic stress helps. Cortisol and testosterone have an inverse relationship. When one rises, the other tends to fall. Any effective stress reduction strategy helps: meditation, exercise, time in nature, good relationships.

Limiting alcohol helps. Heavy drinking damages testosterone-producing cells. Eliminating alcohol entirely shows measurable benefits.

Eating adequate fat and protein supports testosterone production. Testosterone is made from cholesterol, so extremely low-fat diets can reduce testosterone production. Include foods rich in zinc (meat, shellfish, beans, nuts) and vitamin D.

HIIT (High-Intensity Interval Training) shows beneficial testosterone effects. Short, intense exercise bursts work better than endless endurance training. Excessive endurance exercise (marathon training) can actually reduce testosterone.

What TRT Is and When It's Used

TRT is a medical treatment for clinically confirmed hypogonadism (diagnosed low testosterone), not a lifestyle enhancement or anti-aging therapy. It is prescribed by doctors for men who genuinely need it.

Appropriate candidates have two separate morning blood tests confirming total testosterone below 8 to 10 nmol/L. They have symptoms significantly affecting quality of life. Other conditions that could explain symptoms have been ruled out. They have no medical reasons that would make TRT dangerous (like prostate cancer, severe sleep apnea, or desire for future fertility).

TRT is available as injections (every 2 to 4 weeks), gels (applied to skin daily), patches, or long-acting pellets inserted under the skin.

Benefits of TRT for Men With Confirmed Low Testosterone

Improved sex drive and sexual function. Increased muscle mass and reduced body fat. Improved bone density. Better energy and mood. Improved sense of wellbeing and vitality.

The Truth About Over-the-Counter Products

Countless products are marketed as "testosterone boosters" claiming to raise testosterone naturally. The evidence for most of them is either non-existent or comes from tiny, poorly designed studies.

• Tribulus terrestris is heavily marketed but multiple clinical trials show it has no effect on testosterone in men.

• Ashwagandha has some evidence for stress reduction, which may indirectly help. But it does not directly raise testosterone.

• Fenugreek has some evidence for modest increases in available testosterone, but whether this amount actually matters in real life is unclear.

• D-aspartic acid shows mixed results. Some studies show short-term increases that return to normal with continued use.

Some products are found to contain undeclared anabolic steroids. These are genuinely dangerous and illegal. If blood-test confirmed low testosterone is your concern, speak to a doctor about legitimate TRT rather than spending money on unregulated supplements.

Key Points to Remember

Testosterone is genuinely important for men's health. But it is not the measure of a man, and its gradual decline with age is not a disease that requires treatment for most men.

Testosterone decline is part of normal aging, similar to gradual changes in strength or bone density. Some men experience low testosterone that affects quality of life. These men benefit from TRT under medical supervision. Most men maintain adequate testosterone throughout life, even as levels gradually decline.

The lifestyle factors that maintain healthy testosterone are the same ones that maintain health in every other system of the body: regular exercise, adequate sleep, stress management, healthy weight, and good nutrition.

For the minority of men with confirmed clinical hypogonadism (low testosterone confirmed by blood tests with symptoms), TRT under medical supervision can significantly improve quality of life. For everyone else, focus on the fundamentals: move your body, sleep well, manage stress, eat well, and maintain a healthy weight.