ore recently, testosterone (the most important male hormone) supplements have been used by aging men to improve their muscle mass, bone strength, libido and quality of life.
estosterone is a hormone produced by the testicles and is responsible for the proper development of male sexual characteristics. Testosterone is also important for maintaining muscle bulk, adequate levels of red blood cells, bone growth, sense of well-being and sexual function.
Inadequate production of testosterone is not a common cause of erectile dysfunction; however, when ED does occur due to decreased testosterone production, testosterone replacement therapy may improve the problem.

What Causes Testosterone Deficiency?
As a man ages, the amount of testosterone in his body gradually declines. This natural decline starts after age 30 and continues throughout life. Other causes of lowered testosterone levels include:

• Injury, infection, or loss of the testicles.
• Chemotherapy or radiation treatment for cancer.
• Genetic abnormalities such as Klinefelter's Syndrome (extra X chromosome).
• Hemochromatosis (too much iron in the body).
• Dysfunction of the pituitary gland (a gland in the brain that produces many important hormones).
• Inflammatory diseases such as sarcoidosis (a condition that causes inflammation of the lungs).
• Medications, especially hormones used to treat prostate cancer and corticosteroid drugs.
• Chronic illness.
• Chronic kidney failure.
• Liver cirrhosis.
• Stress.
• Alcoholism.

The significance of testosterone decline is controversial and poorly understood.
What Are the Symptoms of Testosterone Deficiency?
Without adequate testosterone a man may lose his sex drive, experience erectile dysfunction, feel depressed, have a decreased sense of well-being, and have difficulty concentrating.
What Changes Occur in the Body Due to Testosterone Deficiency?

• Decrease in muscle mass, with an increase in body fat.
• Changes in cholesterol levels.
• Decrease in hemoglobin and possibly mild anemia.
• Fragile bones (osteoporosis).
• Decrease in body hair.
• Changes in cholesterol levels and lipid levels.

How Do I Find Out If I Have a Testosterone Deficiency?
The only accurate way to detect the condition is to have your doctor measure the amount of testosterone in your blood. Because testosterone levels fluctuate throughout the day, several measurements will need to be taken to detect a deficiency. Doctors prefer, if possible, to test levels early in the morning since this is when testosterone levels are at their highest.
How Is Testosterone Deficiency Treated?
Testosterone deficiency can be treated by:

• Intramuscular injections, generally every two or three weeks
• Testosterone patch worn either on the body or on the scrotum (the sac that contains the testicles)
• Testosterone gel
• Mucoadhesive material applied above the teeth twice a day
• Oral tablets

Each of these options provides adequate levels of hormone replacement; however, they all have different advantages and disadvantages. Talk to your doctor to see which approach may be right for you.
Who Shouldn't Take Testosterone Replacement Therapy?
Men who have prostate cancer or breast cancer should not take testosterone replacement therapy. All men considering testosterone replacement therapy should undergo a thorough prostate cancer screening prior to starting this therapy with a rectal exam and PSA test.
What should I expect from testosterone replacement?
In various clinical studies, very good responses to testosterone have been reported for men with low-testosterone and they include:

• Improvement in mood and sense of well-being 
• Increased mental and physical energy 
• Decreased anger, irritability, sadness, tiredness, nervousness 
• Improved quality of sleep 
• Improved libido and sexual performance 
• An increase in lean body mass, a decline in fat mass 
• An increase in muscle strength (hand grip, upper and lower extremities) 
• Potentially, a decrease in the risk of heart disease

With testosterone therapy, one's attitude improves, reinforcing self-esteem and self-confidence at work, as well as an increased energy at home and in social activities. Most men will feel more vigorous, experience improved energy levels, mood, concentration, cognition, libido, sexual performance and an overall sense of well-being. These effects are usually noted within 3 to 6 weeks.
Other potential benefits include maintenance or improvement in bone density, improved body composition, muscle mass and muscle strength, as well as improvement in visual-spatial skills.

 

What Are the Side Effects of Testosterone Replacement Therapy?
In general, hormone replacement therapy is safe. It is associated with some side effects, including:

• Acne or oily skin.
• Mild fluid retention.
• Stimulation of prostate tissue, with perhaps some increased urination symptoms such as a decreased stream or frequency.
• Breast enlargement.
• Worsening of sleep apnea (a sleep disorder that results in frequent night time awakenings and daytime sleepiness).
• Decreased testicular size.

Laboratory abnormalities that can occur with hormone replacement include:

• Changes in cholesterol and lipid levels.
• Increase in red blood cell count.
• Decrease in sperm count, producing infertility (especially in younger men).
• Increase in PSA

If you are taking hormone replacement therapy, regular follow-up appointments with your doctor are important.
Like any other medication, directions for administering testosterone should be followed exactly as your doctor orders. If you are unsure or have any questions about testosterone replacement therapy, ask your doctor.

Testosterone Therapy for Women

Women normally have circulating in their blood 3 major sex hormones: oestrogen, testosterone and progesterone. Each of these is produced by the ovaries. Oestrogen is also made throughout the body but particularly in body fat. Testosterone can also be made in other parts of the body from hormones (DHEA and DHEAS) that are produced by the adrenal glands. At the time of natural menopause or surgical removal of the ovaries oestrogen and progesterone levels fall precipitously. Testosterone and DHEAS levels however fall more gradually with increasing age such that a woman in her forties has on average only half of the testosterone and DHEAS circulating in her bloodstream as does a woman in her twenties. After a woman has her ovaries removed by surgery testosterone levels can fall by up to fifty percent. However testosterone does not change across menopause, although this varies somewhat between women. Testosterone and other related hormones (DHEA and DHEAS) in the body (also known as androgens) have known physiological roles in women. Firstly, oestrogen is actually made from testosterone and DHEA, and without the ability of our bodies to make testosterone we cannot make oestrogen. Testosterone and DHEA appear to have direct independent effects in different parts of the body, and some women may experience a variety of physical symptoms when their blood levels fall. Such symptoms may include: impaired sexual interest (loss of libido or sexual desire), and lessened sexual responsiveness lessened wellbeing, loss of energy. Testosterone therapy may be beneficial for some women who have had their ovaries surgically removed or in some cases who have significant symptoms in the form of loss of libido, fatigue and diminished wellbeing. Caution  Testosterone therapy will not be the answer for someone who has a poor partner relationship, depression or poor wellbeing due to other causes. Measuring Testosterone All women should have a blood test to measure their testosterone level before starting any testosterone replacement mainly to exclude higher levels of testosterone. There is no set level of testosterone below which suggests or guides treatment, but it is essential that women with normal or high levels are not misdiagnosed and treated with androgens. Women should also have thyroid disease and iron deficiency excluded as possible causes of their symptoms by having a blood test for these conditions. Most methods for measuring testosterone are fairly imprecise and become even more inaccurate when blood levels of testosterone are low. Blood should be taken ideally between 8:00am and 10:00am as testosterone levels vary throughout the day. For women who have regular cycles, blood should not be taken during the menstrual phase as testosterone levels are low at this time in most women and thus the result may be misleading. Thus blood should be drawn at least 8 days after the start of menstruation. Recent Jean Hailes research has shown no relationship between testosterone levels and loss of libido and sexual dysfunction. Therefore levels cannot be used to diagnose androgen insufficiency, only to ensure levels are not elevated. Levels of testosterone also cannot guide replacement of testosterone. The factors that do influence libido are discussed by psychologist  Dr Amanda Deeks PhD, in her "10 tips for understanding and improving your libido".