Testosterone is a male hormone that plays a key role in muscle development, bone mass, fat distribution, sex drive, sperm production, mood, and red blood cell production.

Testosterone levels naturally start to decline by a rate of about 1% each year beginning at age 30. By age 70, roughly 30% of men will have lower-than-normal testosterone levels.

One of the most common symptoms of low T is a noticeable decrease in muscle mass associated with weight gain.

“Loss of muscle is called muscle wasting, and it’s a late sign of low T,” explains Ronald Tamler, MD, an associate professor at the Icahn School of Medicine at Mount Sinai in New York City. “But even before muscle wasting, you may feel weaker and less energetic.”

Other symptoms of low T include:

• Hair loss
• Fatigue
• Irritability
• Low libido
• Depression

Testosterone communicates with muscle tissue through special proteins called androgen receptors (ARs). When activated by testosterone, the ARs signal the body to produce muscle cells.

In men with normal T levels, muscle mass is determined by the number of androgen receptors rather than the level of testosterone.

In men with low T levels, muscles begin to deteriorate and fat deposits increase. The body responds to excess fat by producing an enzyme called aromatase. This enzyme converts testosterone to estrogen, leading to increased fat around the chest, hips, belly, and thighs.

Meanwhile, the other symptoms of low T make it even more difficult to exercise. It can be a vicious cycle.

You can mitigate the effects of low T by exercising, getting enough sleep, and maintaining a balanced diet, but the best way to avoid the effects of low T is to maintain a healthy weight before testosterone levels start to decline.

Does testosterone therapy help?

Increased lean body mass and gains in muscle strength are two of the best documented effects of testosterone therapy.

In terms of muscle mass, numerous studies suggest that older men will benefit from T therapy just as much as younger men.

According to a meta-analysis conducted in 2018, testosterone injections are up to 3x more effective than testosterone gels for building muscle strength.

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