What Is Low Testosterone?

You hear about “Low T” all the time, and are well aware of the hormone ‘testosterone’’s benefits. But, what exactly is it?

Testosterone is necessary in both men and women and declines steadily after age 30.

At Optimal Levels, Research Shows Testosterone Increases:

  • Bone Density
  • Bone Formation
  • Energy
  • Sex Drive
  • Muscle Mass
  • Decreases Body Fat
  • Lowers Blood Pressure
  • Regulates Cholesterol Levels

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Despite Testosterone being the principal male sex hormone, it plays an essential role in both men and women’s overall health and wellness.

This naturally occurring steroid hormone is found in mammals, reptiles, birds and other vertebrates. Home to the ‘Androgen Group’*, testosterone contributes to the growth of male sex organs and the development of sex characteristics.

*Androgens were first discovered in 1936 and are the precursor of all estrogens. Testosterone is the most well-known androgen hormone. However, Dihydrotestosterone (DHT and androstenedione are less known, but of equal importance in male development).

Testosterone’s Effect On Early Human Development

Testosterone is essential in pre-birth development, puberty and plays a critical role in the years long after your high school days.

Lets Start At The Beginning

While your XX Chromosomes (if you’re female) or XY Chromosomes (if you’re male) formed in the womb, they determined your chromosomal sex. Your chromosomal sex determines gonadal sex, which is the sex that will be apparent as your sex organs develop and mature.

Men: The presence of your Y chromosome induced the formation of your testicles.
Two hormones most important to this process are testosterone and anti-Mullerian hormone (a hormone that suppresses the growth of female sex organs). Both of these essential hormones were produced by your testes.

Masculinization results from the ability of testosterone to induce male genitals and secondary male sex characteristics.
Women: The absence of your Y chromosome allowed you to follow your female developmental pathway. Interestingly, from a genetic standpoint, femaleness is the default setting, because no specific hormones are required for the formation of female genitalia.

Your determined sex organs will secreted essential hormones during your early childhood development.

Specific Prenatal Androgen Effects At Two Developmental Stages:

1. Gestation (between 4-6 weeks):

  • Genital Virilization: Androgens; Dihydrotestosterone (DHT) and testosterone determined midline fusion, phallic urethra, scrotal layers and vaginal rugation.

  • Prostate and vesicular gland development

  • A surge in testosterone causes the male genitalia to develop and causes specific areas of the male brain to develop. An absence of testosterone causes the fetus to remain female (the default sex).

2. Second Trimester (Weeks 13-19):

  • Sexual Differentiation Of The Brain: This stage determines the feminization or masculinization of the baby. Interestingly, the mother’s testosterone levels during the second trimester are a better predictor of her daughter’s behavior than the daughter’s own adult testosterone levels. [Biology at Work: Rethinking Sexual Equality]

First Weeks Of Life:

  • Male: Testosterone levels rise in male infants to levels typical in a pubertal range, then fall back to barely detectable level by 4-6 months of age. This spike in male infant’s testosterone levels is still somewhat unknown.

  • Some researchers think it’s the brain’s masculinization stage. Where the male brain is becoming masculinized by the aromatization of testosterone into estrogen, (so it’s able to cross the blood-brain barrier in order to enter the brain).

  • Female: Infant females have alpha-fetoprotein, which binds up the estrogen so female brains are not affected.

To be clear, hormones in these early stages do not cause sexual behavior. They alter the activity in various brain areas to change the way the brain will respond to external stimuli.

The Awkward Years (Pre-peri pubertal & Pubertal Stages)

You remember those awkward years in your teens? The new body odor, body hair and acne.

Teenage girls can experience a pubertal stage for months or years until their androgen levels fall back below a normal adult level. While teenage boys usually experience later pubertal changes when their free testosterone levels rise in their blood.

What is “Low Testosterone”?

When your testosterone levels fall below 300 nanograms per deciliter (ng/dL) you begin to experience the effects of low testosterone.
Andropause – A term commonly referred to as the male counterpart to menopause and is caused by a drop in testosterone.
Main Symptoms of Low Testosterone:



Loss Of Muscle Mass


Increase In Body Fat

Increased Body Fat

Low Sexual Desire

Loss Of Body Hair

Decreased Bone Strength

Difficulty Focusing

Poor Concentration

Low Libido



Sexual dysfunction (inability to maintain erections)

Decreased Bone Strength

Loss of body hair

Mood Swings

Low Semen Volume


Mood Swings