What is Testosterone?

If you’ve ever found yourself wondering, “What is testosterone?” Then you’re not alone. Many of us know that testosterone has a part to play in the reproduction process but may not be clear on testosterone’s various roles in our bodies.

What Is Testosterone? And What Does Testosterone Do?

If you’re looking for the testosterone definition, here’s one from the National Institutes of Health: Testosterone is a hormone made mainly in the testes (part of the male reproductive system). It is needed to develop and maintain male sex characteristics, such as facial hair, deep voice, and muscle growth.

What Is Testosterone Used For?

While we know that testosterone is needed to produce sperm, it is also responsible for many processes during a man’s lifecycle. It is a significant sex hormone and has a vital role in sperm production. In addition, it is involved in several other functions, such as:

• The development of the penis and testes
• The deepening of the voice during puberty
• The appearance of facial and pubic hair
• Muscle size and strength
• Bone growth and strength
• Sex drive (libido)

Found in both men and women, Testosterone starts to be produced during puberty and starts to decline by about 1-2% a year after the age of 30.

Where Is Testosterone Produced in the Body?

Hormones are chemical messengers that trigger changes and processes in the body. The brain’s hypothalamus and pituitary glands, located at the base of the brain, control testosterone production. To produce testosterone, the hypothalamus instructs the pituitary gland on how much testosterone to make; the pituitary gland then sends a message to the gonads. In the gonads, the Leydig cells create and secrete testosterone, and the adrenal glands also produce small amounts.

A loop between the pituitary gland and the testes regulates the amount of testosterone in the blood, controlling the amount of the hormone produced.

Women’s ovaries also produce testosterone, but in much smaller quantities.

What Is Low Testosterone?

According to American Urological Association (AUA) guidelines, a normal testosterone level is at least 300 nanograms per deciliter (ng/dL), so below this would be considered low testosterone.

Low testosterone in men can cause physical symptoms, such as:

• Decreased sex drive
• Erectile dysfunction
• A higher percentage of stomach fat
• Development of breast tissue (gynecomastia)
• Infertility
• Lack/loss of body hair
• Voice doesn’t deepen
• Low muscle mass
• Slowed growth of the penis or testicles

Possible Causes of Low Testosterone

A man’s testosterone level is highest around 18/19 and will naturally decrease as a man gets older. However, certain factors can cause hormone levels, such as testosterone, to drop. The good news is that some men who have a testosterone deficiency or have symptoms or medical conditions related to testosterone will find their symptoms improve when they take testosterone replacement therapy (TRT). For example, a man who has osteoporosis and low testosterone could have TRT, increasing bone strength and reducing fracture risk.

Some of the potential causes of low testosterone in men include:

• Chronic health conditions, such as diabetes
• Damage to the testes, such as from physical trauma, alcoholism, or viral illnesses
• Genetic diseases, including Klinefelter, Kallman, or Prader-Willi syndromes
• Hypothalamic disease or tumor
• Pituitary disease or tumor
• Testicular failure

So, if you were wondering, “what is testosterone?” Hopefully, your question has now been answered in this article by our expert team.

When to See a Doctor

Talking about low energy, lost muscle, and a decreased sex drive probably isn’t a fun conversation for anyone to have. If you’re concerned about your testosterone levels and are experiencing any of the below symptoms, consider speaking with a men’s health doctor.

If you’re experiencing any of these symptoms, it may be time to speak to a doctor:

• Decreased sex drive (libido)
• Difficulty achieving or maintaining erections
• Fatigue
• Decrease in muscle mass
• Low mood or low feeling of wellbeing
• Low energy or feeling sluggish/lethargic
• Difficulty concentrating
• Depression or low mood
• Hot flashes or sweats
• Poor concentration
• Interrupted sleep

Testosterone as a Steroid Hormone

Testosterone is the body’s principal male sex hormone, and it belongs to the steroid class of hormones. Your body produces testosterone naturally. In this sense, steroid is a chemical classification. In ordinary use, anabolic steroids usually refers to testosterone derivatives taken at non-replacement doses to improve performance or appearance.² A third meaning is legal. The FDA prescribing information for Depo-Testosterone classifies testosterone as a Schedule III controlled substance under the Controlled Substances Act.³

Testosterone replacement therapy (TRT) uses a steroid hormone. Prescribed TRT is a separate clinical activity from what people usually mean by steroid use. The Endocrine Society clinical practice guideline recommends therapy for men who have symptoms and signs of testosterone deficiency plus consistently low morning total testosterone results.¹ The guideline calls for a repeat morning measurement to confirm the result. It also calls for a discussion of benefits, risks, and monitoring before treatment begins.¹ Diagnosis and dose distinguish prescribed therapy from non-prescribed use.

The anabolic-steroid literature examines a different setting. A systematic review and meta-analysis of 33 studies included 3,879 participants and reported a statistically significant reduction in luteinizing hormone during anabolic-steroid use.² The authors wrote that anabolic-steroid use may cause serious and potentially irreversible adverse effects across several organs and systems, including the reproductive system.² Those findings concern anabolic steroid use at non-replacement doses. The review did not report outcomes from prescribed TRT.

The word on a bottle cannot determine whether testosterone therapy fits your health. A fasting morning testosterone blood test, a repeat measurement, and a physician's review of your symptoms provide the information needed to make that decision.¹

Here at Opt Health, we have specialized men’s health doctors who can provide treatment from the comfort of your own home. We offer preventative medicine to increase men’s vitality and testosterone replacement therapy for men.

Our guide to what a high testosterone result means covers what an elevated result usually means and the workup that finds the cause.

This content is for informational purposes and does not replace evaluation, diagnosis, or treatment by a qualified medical professional.