There is a progressive decline in testosterone production within men’s body, as age ticks on. These changes can be dramatic, considering that 50% of men aging over 60, have low levels of testosterone. The rate of decline varies widely. But a general rule of thumb is that testosterone levels decrease about 1% yearly after the age of 50.
Despite the fact that it is not as rapid a drop in hormones as women get with menopause, it certainly is just as real. So technically, this has been termed male menopause, male climacteric, andropause, or more appropriately, partial androgen deficiency in the aging male (PADAM).
Serum testosterone levels in men drop progressively from the third decade to the end of life, mainly due to a decline in the cells in the testis that makes the hormone (Leydig cells). This decline may also be due to changes in hormones (GnRH, LH) and proteins (SHBG, albumin) that regulate testosterone production.
NORMAL TESTOSTERONE LEVELS
One issue with testosterone that complicates matters is the fact that it exists in several different forms in the blood, and each form has different hormonal activity (Figure 1). “Free” or unbound testosterone is a fully active hormone, but protein-bound testosterone are only partly active, or sometimes completely inactive. What is usually measured in a blood draw is the total testosterone, which is a combination of the free and protein-bound forms. An analogy to explain this is to think of the total testosterone as all of the cars in a parking lot. Importantly, though, only the cars that can start or drive are useful or active. Free testosterone comprises all of the cars that can start and be driven away. But the protein-bound testosterone are those cars that may or may not start, and those that may or may not be able to be driven away. So, aging is associated with 1) lower total testosterone production (fewer cars in the lot) and 2) higher levels of certain proteins that bind testosterone (sex hormone-binding globulin, SHBG), considering that even fewer cars can start and run, and it is this combination of events that leads to declining testosterone activity with age. Thus, the complex physiology of testosterone balance often clouds the interpretation of age-related declining levels of the hormone.
THE ROLE OF TESTOSTERONE IN MEN
Testosterone affects the function of many organs in the body. In the brain, it influences libido or sex drive, male aggression, mood and thinking. Testosterone can improve verbal memory and visual-spatial skills. It has also been shown to decrease fatigue and depression in men with low levels. It is responsible for muscle strength and growth, and stimulates stem cells and blood cells in bones and kidneys. Penile growth, erections, sperm production, and prostatic growth and function all depend on testosterone. It also causes body hair growth, balding, and drives beard growth. Thus, testosterone makes us who we are, and influences how we look.
TESTOSTERONE EFFECTS IN THE NORMAL MALE
MALE SEX ORGANS Growth, development, maintenance of secondary sex characteristics; sperm production, erections and prostatic function.
BEHAVIOR Improved libido, mood, memory and energy.
BONE Linear growth, closure of the epiophyses, increases bone mineral density.
FAT TISSUE Body and abdominal fat reduction.
MUSCLE Anabolic; increases muscle mass and strength.
LIVER Stimulates production of serum proteins.
KIDNEY Stimulates erythropoietin production which increases blood counts.
HEART Dilates blood vessels in the heart.
BLOOD Suppression of clotting factors (II, V, VII), low HDL-cholesterol.
BONE MARROW Stimulates stem cell production.
HAIR Influences body hair growth, especially facial hair.
ADVANTAGES OF TESTOSTERONE REPLACEMENT THERAPY
In the case of men with low testosterone levels, testosterone can improve bone mineral density and reduce bone fractures; an effect similar to that found in postmenopausal women on estrogen replacement. Importantly, hip fractures are 2-3 times as likely to kill an older man as a woman of the same age, and 40% of older male patients with hip fractures die within 1 year of the injury.
Testosterone results in increase in lean body mass, possibly strength and can decrease fat mass. By stimulating erythropoietin, testosterone increases blood counts. It appears to improve lipid profiles and dilates blood vessels in the heart but no data has yet shown that it reduces heart attacks or strokes. It appears not to alter LDL or total cholesterol levels. In recent work, it has been shown that men with chronically low testosterone levels have 2-3 fold higher risk of developing metabolic syndrome and have up to a 40% greater risk of death than men with normal testosterone levels.
BETTER SEXUAL HEALTH
Sexual function also improves with testosterone. Most studies agree that sexual drive is improved by testosterone. Penile erections may be improved with testosterone, but only in men with low testosterone levels. It’s an important fact that isolated low testosterone is an unusual (6%) cause of erectile problems in older men as lower sex drive and age-related changes to the penis are far more common.
LOW TESTOSTERONE SYMPTOMS AND DIAGNOSIS
To make an accurate diagnosis of low testosterone, symptoms or findings must accompany a blood draw showing a low testosterone level. This combination makes the treatment worthwhile to pursue. Symptoms include decreased sexual desire and erectile dysfunction, changes in mood associated with fatigue, depression and anger, and decreases in memory and spatial orientation ability. On examination, there may be decreases in lean body mass with reduced muscle volume and strength, and increases in abdominal girth. Decreased or thinning of facial and chest hair and skin alterations such as increases in facial wrinkling and pale-appearing skin suggestive of anemia may also be noted. Testicles that have become smaller or softer may also be present. Finally, low bone mineral density with osteopenia or osteoporosis may also suggest a problem.
Not all of these findings need to be present at the same time to diagnose the problem. In fact, many of these symptoms can be attributed simply to the natural and unavoidable consequence of aging. For example, frailty may be due to many causes, some of which include loss of muscle strength, bone fractures, decreased mood, and impaired cognition; symptoms typical of testosterone deficiency. However, the association of such symptoms along with a low testosterone certainly implicates this as a problem. By these criteria, it is estimated that only 10% of men with low testosterone levels are currently being diagnosed.
Because testosterone is found in several forms in the blood, there is debate as to what test is best to diagnose testosterone deficiency. In general, a total testosterone is ordered first. National guidelines suggest that a testosterone level below 300 mg/dL is suspicious for being low, but obviously this will vary among men. Evidence of a prior testosterone level that is much higher than a current level might warrant treatment even if the current level is > 300ng/dL. Presently, measuring testosterone byproducts such as dihydrotestosterone (DHT), estradiol and dihydroandrosteindione (DHEA) is not that useful in making the diagnosis.
Although not used in all cases, a blood count showing anemia may help to make the diagnosis. In addition, a DEXA scan is an accurate, quick and painless procedure for measuring bone density or bone loss. The amount of radiation used for this X-ray technique is extremely small – less than 1/10 the dose of a standard chest x-ray. Bone density assessments can also be performed periodically during testosterone replacement to assess the bone response to treatment. Certainly an evaluation for prostate cancer with a PSA and rectal examination is indicated in men who are at risk prior to testosterone treatment.
TREATMENT FOR LOW TESTOSTERONE LEVELS
The ideal testosterone therapy maintains normal concentrations of the hormone without having significant side effects. Several kinds of hormone replacement are currently available at The IMT Clinic, including oral, injectable, transdermal and buccal mucosal systems.
MONITORING OF TESTOSTERONE THERAPY
Testosterone replacement is generally considered a long term therapy and patients need to be monitored regularly. Prior to starting treatment, a digital rectal examination and serum PSA are important. Within a month or two after treatment has started, symptoms and testosterone levels should be assessed. During the first year of therapy, patients should be followed regularly to assess clinical response. After the first year, patients who are stable may be followed annually.
Annual evaluations should include testosterone, hemoglobin, liver function tests, lipid profile and PSA tests. Bone density and psychological evaluations can be done depending on the original reasons for treatment.