Testosterone is an important male hormone. A male begins to produce testosterone as early as seven weeks after conception. Testosterone levels rise during puberty, peak during the late teen years, and then level off. After age 30 or so, it’s normal for a man’s testosterone levels to decrease slightly every year.
Most men have more than enough testosterone. But, it’s possible for the body to produce too little testosterone. This leads to a condition called hypogonadism. This can be treated with hormonal therapy, which requires a doctor’s prescription and careful monitoring. Men with normal testosterone levels should not consider testosterone therapy.
Testosterone levels affect everything in men from the reproductive system and sexuality to muscle mass and bone density. It also plays a role in certain behaviors.
The body’s endocrine system consists of glands that manufacture hormones. The hypothalamus, located in the brain, tells the pituitary gland how much testosterone the body needs. The pituitary gland then sends the message to the testicles. Most testosterone is produced in the testicles, but small amounts come from the adrenal glands, which are located just above the kidneys. In women, the adrenal glands and ovaries produce small amounts of testosterone.
Before a boy is even born, testosterone is working to form male genitals. During puberty, testosterone is responsible for the development of male attributes like a deeper voice, beard, and body hair. It also promotes muscle mass and sex drive. Testosterone production surges during adolescence and peaks in the late teens or early 20s. After age 30, it’s natural for testosterone levels to drop by about one percent each year.
About seven weeks after conception, testosterone begins helping form male genitals. At puberty, as testosterone production surges, the testicles and penis grow. The testicles produce a steady stream of testosterone and make a fresh supply of sperm every day.
Men who have low levels of testosterone may experience erectile dysfunction (ED). Long-term testosterone therapy can cause a decrease in sperm production. Testosterone therapy also may cause enlarged prostate, and smaller, softer testicles. Men who have prostate or breast cancer should not consider testosterone replacement therapy.
During puberty, rising levels of testosterone encourage the growth of the testicles, penis, and pubic hair. The voice begins to deepen, and muscles and body hair grow. Along with these changes comes growing sexual desire.
There’s a bit of truth to the “use it or lose it” theory. A man with low levels of testosterone may lose his desire for sex. Sexual stimulation and sexual activity cause testosterone levels to rise. Testosterone levels can drop during a long period of sexual inactivity. Low testosterone can also result in erectile dysfunction (ED).
Central Nervous System
The body has a system for controlling testosterone, sending messages through hormones and chemicals that are released into the bloodstream. In the brain, the hypothalamus tells the pituitary gland how much testosterone is needed, and the pituitary relays that information to the testicles.
Testosterone plays a role in certain behaviors, including aggression and dominance. It also helps to spark competitiveness and boost self-esteem. Just as sexual activity can affect testosterone levels, taking part in competitive activities can cause a man’s testosterone levels to rise or fall. Low testosterone may result in a loss of confidence and lack of motivation. It can also lower a man’s ability to concentrate or cause feelings of sadness. Low testosterone can cause sleep disturbances and lack of energy.
It’s important to note, however, that testosterone is only one factor that influences personality traits. Other biological and environmental factors are also involved.
Skin and Hair
As a man transitions from childhood to adulthood, testosterone spurs the growth of hair on the face, in the armpits, and around the genitals. Hair also may grow on the arms, legs, and chest.
A man with shrinking levels of testosterone actually may lose some body hair. Testosterone replacement therapy comes with a few potential side effects, including acne and breast enlargement. Testosterone patches may cause minor skin irritation. Topical gels may be easier to use, but great care must be taken to avoid transferring testosterone to someone else though skin-to-skin contact.
Muscle, Fat, and Bone
Testosterone is one of many factors involved in the development of muscle bulk and strength. Testosterone increases neurotransmitters, which encourage tissue growth. It also interacts with nuclear receptors in DNA, which causes protein synthesis. Testosterone increases levels of growth hormone. That makes exercise more likely to build muscle.
Testosterone increases bone density and tells the bone marrow to manufacture red blood cells. Men with very low levels of testosterone are more likely to suffer from bone fractures and breaks.
Testosterone also plays a role in fat metabolism, helping men to burn fat more efficiently. Dropping levels of testosterone can cause an increase in body fat.
Testosterone therapy can be administered by a doctor via intramuscular injections.
Testosterone travels around the body in the bloodstream. The only way to know your testosterone level for sure is to have it measured. This usually requires a blood test.
Testosterone spurs the bone marrow to produce red blood cells. And, studies suggest that testosterone may have a positive effect on the heart. But some studies investigating testosterone’s effect on cholesterol, blood pressure, and clot-busting ability have had mixed results.
When it comes to testosterone therapy and the heart, recent studies have conflicting results and are ongoing. Testosterone therapy delivered by intramuscular injection may cause blood cell counts to rise. Other side effects of testosterone replacement therapy include fluid retention, increased red cell count, and cholesterol changes.
The FDA has approved the first nasal testosterone replacement therapy for use in men suffering from conditions associated with a deficiency or absence of endogenous testosterone.
The product, Natesto, is self-administered via a nasal applicator, thus minimizing the risk of exposing women and children to testosterone. One pump actuation delivers 5.5 mg of testosterone. The recommended dose of Natesto is 11 mg of testosterone (2 pump actuations, one per nostril), applied intranasally three times daily for a total daily dose of 33 mg.
The preparation is contraindicated in men with breast cancer or known or suspected prostate cancer.
In a press release, the drug's maker, Trimel Pharmaceuticals Corp., of Toronto, said patients with benign prostatic hyperplasia should be monitored for worsening signs and symptoms.
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