The eight symptoms that follow aren’t proof of low testosterone on their own. You’ll need two blood tests showing low levels—usually around 300 nanograms per declileter (ng/dL) or lower, depending on the lab—before your doctor makes an official low testosterone diagnosis,
Perhaps the best-known, quickest, and most common effect of low T is low libido, says urologist.
In fact, nearly every patient who comes to his office with known or suspected low T complains of a lack of sexual appetite. Besides wanting less sex, men with low T may also masturbate less and report fewer fantasies and erotic dreams.
Brain areas involved with sexual desire, including the amygdala, are packed with testosterone receptors.
The hormone fits inside them like a lock inside a key, lighting them up to arouse you. Without it, you’re missing a critical step in the turn-on process.
This lack of desire to have sex can cause problems with erections, though low T doesn’t directly affect the plumbing involved in getting or staying hard, Dr. Ramin says.
Ample testosterone puts your body in an anabolic, or muscle-building, state by helping your body produce and assemble proteins that form the building blocks of lean mass.
When your testosterone levels drop, your body turns catabolic instead, breaking down muscle tissue instead of building it up, Dr. Werthman says.
At first, you might notice that it’s tougher to push as much weight at the gym or build muscle, he notes.
And after a few weeks of low T, you can expect to lose muscle mass.
In fact, in one Japanese study, men with low free testosterone levels—a measure of the amount of hormone available to bind to receptors—had double to triple the risk of muscle loss with aging as those with normal levels.
Without a steady flow of testosterone, the tissues in your penis, scrotum, and testicles can atrophy, or shrivel.
As a result, your penis might lose length and girth. You may notice your balls shrink, too—they often shrivel to half the size and turn squishy instead of firm, he says.
Though testosterone replacement therapy won’t bring back your testicular volume, when it comes to your penis, the treatment “has a good chance of restoring its glory.
Even as you lose size where it counts, you gain it where it hurts, Dr. Anawalt says.
In one Australian study, men with prostate cancer gained 14 percent more body fat and 22 percent more visceral fat after one year of androgen deprivation therapy, a treatment which turns off testosterone’s effects.
Visceral fat is the deep abdominal fat that forms around your organs and increases your risk for diabetes and heart disease.
In men, low testosterone may increase the activity of an enzyme called lipoprotein lipase, the study authors suspect. This compound drives circulating building blocks called lipids into visceral fat cells, plumping them up.
Trouble with thinking and memory often occurs in men with low T.
In 2015 study from Australia, men whose testosterone levels declined over 5 years also experienced a drop in scores on tests of their mental function and memory.
Besides the amygdala, areas of the brain important for memory and attention—such as the cerebrum—also have testosterone receptors.
When there’s not enough of the hormone pumping in to those receptors, your brain cells may not be able to function as well, the study authors note.