Low levels of Testosterone in men
Testosterone is the male hormone mainly synthesized by the interstitial cells of Leydig which constitute around 20% of the mass of adult testis. The hormone is essential for the differentiation into the male-type body. During fetal stages, testosterone promotes the development of male organs and the descent of testes from the abdomen into the scrotum. The chances of malignancy increased to 40-fold if testes fail to reach the scrotum (1). At the onset of puberty, testosterone brings about the enlargement of scrotum, penis, testes, and development of secondary male sexual characters, e.g. male-type hair distribution and masculine voice (2). Testosterone also increases the basal metabolic rate (BMR), muscle bulk, red blood cells count and stimulate the formation of longer and thicker bones.
Age-Wise Fluctuation in Testosterone Levels
The normal range of testosterone hormone is taken around 270-1070ng/dL in males (3). But the values vary with age and a bimodal distribution is seen if age-wise testosterone levels are plotted in the graph. The normal range of serum testosterone levels in men is given below (4).
|Age||Testosterone level (ng/dL)|
|0-5 months||75 – 400|
|6 months – 9 years||<7 – 20|
|10 – 11years||<7 – 130|
|12 – 13 years||<7 – 800|
|14 years||<7 – 1200|
|15 – 16 years||100 – 1200|
|17 – 18 years||300 – 1200|
|19+ years||240 – 950|
|21 – 30 years||270 – 1070|
|30+ years||1% decline per year|
Testosterone deficiency is a fairly common disease. As estimated 3 out of 10 men above the age of 60 and 4 out of 10 above the age of 70 have low levels of testosterone hormone (5). A study that included 2117 men between the ages 20-79 found that more than 10% of men had testosterone levels below the normal value for each age range (6). The low levels of testosterone are more prevalent in people with added comorbidities such as hypertension, diabetes, dyslipidemia, obesity, asthma, chronic obstructive pulmonary disease, and prostate disorders (7).
Significance / Impact of Low Testosterone on Health
A range of signs and symptoms appear in men with low levels of testosterone. Not all the men face the same manifestations of testosterone deficiency in equal severity.
Loss of Libido
Testosterone is the main regulator of male sexual drive. When the levels of testosterone fall, the sexual appeal also takes a dive (8). The interest in sex weans off drastically as compared to the gradual loss of interest in sex with age and the “performance” during intercourse is also reduced, causing unhappy relationships and increased stress. The desire to masturbate is also decreased contributing to overall sluggish behavior of male.
According to a study, 19% of the patients with low levels of testosterone exhibited loss of sexual desire (9) but the extent of decreased libido exact value of testosterone levels remains subjective.
Low Sperm Count
Testosterone is required for spermatogenesis – the process of sperm production and maturation. Testosterone binds to androgen binding receptors in the Sertoli cells of the testis that are responsible for synthesis, nourishment, and storage of sperms. In the absence of testosterone hormone, not only the spermatogenesis stops at Meiosis I phase but the stored sperms also die because of nutrient deficiency (10).
The insufficient and poor quality sperms lead to infertility and can be detected in semen analysis. If a couple has a problem conceiving, the low levels of the male hormone could be one of the causes.
The inability to get an erection or maintain a harder erection required for penetration is called Erectile Dysfunction (ED). ED is one of the main causes of infertility where the cause lies in the male partners. Besides the other cause of ED, low circulating levels of testosterone are one of them.
As discussed before, testosterone regulates male sexual drive by binding to receptors in the central nervous system. The same hormone is also responsible for the release of nitric oxide (11) – a chemical messenger that dilates the penile arteries to allow more flow of blood for harder erection. Thus the low testosterone levels will lead to fewer and unsustained erections. Interestingly, the nocturnal erections are also testosterone dependent and will be infrequent in such a scenario (12).
While the male hormones are notorious for causing the pattern baldness, they play an important role in the growth of the development of hair throughout the body, especially fascial hair which are part of male secondary sexual characters.
Alopecia or hair loss refers to the loss of hair from the head or any part of the body. It is not a sudden thing to happen overnight but starts gradually with thinning of hair and ultimately leading to hair loss. It can be temporary or permanent, depending on the underlying cause. There are different types of hair loss, one of the common types is Androgenetic alopecia. Dihydrotestosterone (DHT) – a product of Testosterone – is responsible for such hair loss.
Contrary to this, healthy levels of testosterone are required for facial hair growth. A study concluded that men with higher levels of testosterone and dihydrotestosterone can grow a dense beard compared to others. Testosterone causes priming of the hair follicles whereas the DHT accelerates the linear growth of strands (14).
The male steroid hormone is well known for its anabolic benefits for a long time. The testosterone binds to intracellular receptors in the muscles and increases the update of amino acids – the building blocks of proteins. This results in increased muscle mass and strength with higher testosterone levels but the two are not directly proportional. Although the research shows that higher testosterone levels are associated with more muscle bulk, the effect reached the plateau phase after a certain level. The exercise-induced muscle strength is actually directly linked to the availability of androgen receptors – the site of testosterone binding (15,16).
Likewise, the decrease in serum testosterone levels is associated with decreased muscle bulk and if combined with lack of physical activity, it could result in a significant loss in muscle size and strength.
The testosterone hormone also plays a role in fat metabolism by decreasing the amount of fat deposition, especially in the hips, belly, and chest – the reason for male type body. The decrease circulating levels of testosterone promotes obesity and more fat deposition throughout the body. A study found that low testosterone levels are associated with an increased incidence of obesity which in turn further lowers the production of testosterone by the Leydig cells – thus a vicious cycle sets in (17). Moreover, the fat cells increase the production of the aromatase enzyme which starts converting the free testosterone into estrogen. This adds fuel to fire and further promotes obesity in men already having low levels of testosterone.
Osteoporosis literally means “hole in the bone”. It is a disease characterized by soft and porous bones due to decreased bone synthesis, increased bone resorption, or both. The disease is more common in women of post-menopausal age due to low estrogen levels but it also has increased incidence in men with low levels of testosterone (18).
Testosterone, as stated before, is an anabolic hormone. It leads to increased activity of osteoblasts (bone-forming cells), inhibits the activity of osteoclasts (bone-eating cells), and retard the apoptosis (death) of osteocytes – the bone cells (19). In the absence of sufficient quantities of testosterone, the tensile bone strength is reduced leading to increased incidence of bone fractures and bone pains.
Mood swings / irritability/ Sleep disturbance
Hormonal fluctuations have a great impact on someone’s mood. Although this phenomenon is more common in women with a monthly cycle of hormonal changes, it can be found in men with low levels of sex hormones. Testosterone is proven to increase anger and hostility in male (20)- a primitive response of manly protection of territories. It also acts as a mood stabilizer and promotes a healthy sleep-wake cycle.
Deficiency of testosterone hormone can sometimes manifest in the same manner as female menopause – thus andropause in males is also known as “male menopause” (21). The psychological symptoms of male menopause include:
- Low mood
- Hot flashes
- Decreased motivation
- Insomnia or problem getting sleep
- Difficulty concentrating
- Loss of self-confidence
In a study comprising of males with hypogonadism, the low levels of androgens production were overcome with testosterone replacement. After 6 months of treatment, a significant improvement in anxiety, libido, depression, and quality of life was seen, suggesting a link between low levels of testosterone and increased incidence of psychological symptoms (22).
The diagnosis of testosterone deficiency lies in the appearance of signs and symptoms discussed above. It is advisable to visit a physician and get your testosterone levels checked rather than assuming the deficiency of hormone and starting self-medications. Although the development of clinical signs of testosterone deficiency is supportive of the disease, they’re inadequate to provide sufficient grounds and still warrant laboratory investigations.
Testosterone levels can be measured by two methods:
- Blood test – The reference levels of testosterone by age distribution has been shown in Table 1. A simple blood test performed in the laboratory is enough to check testosterone levels in the blood. The values are in ng/dL and compared with the reference ranges to reach a diagnosis.
- Saliva test – This is a simple test in which the person spits into a container and the level of hormones is tested. The values are in pg/dL.
Sometimes, the doctor may advise adjuvant tests to evaluate complications of testosterone deficiency i.e blood counts, blood sugar levels, lipid profile, bone scans, and semen analysis.
If the testosterone levels are found low, further investigations can be ordered to find the cause of hypogonadism. These tests include:
- FSH and LH levels
- MRI of brain
- Genetic testing
The treatment of testosterone deficiency is pretty straightforward. Testosterone is supplemented exogenously in the form of:
- Gel applied topically once daily.
- Patch placed on a part of the skin once daily.
- Injections given at 2-4 weeks interval at a doctor’s clinic of self-administered at home.
- Nasal gel applied onto the inner side / onto mucosa of the nose.
- Testosterone Implants can be implanted under the skin, especially in the upper right arm and left there for a period of 3 to 6 months. They provide a sustained release of the hormone and avoid fluctuations in plasma levels.
- Testosterone boosters diets can increase the endogenous production of the hormone if the deficiency is not due to any pathologies.
Although the treatment with testosterone replacement generally improves physical symptoms, increase muscle bulk, and improves psychological manifestations, it still fails to improve erectile dysfunction, cardiovascular risk, and cognitive problems (23).
A healthy diet rich in beef, oysters, eggs, milk, vitamin D, tuna, beans, and shellfish can help in boosting testosterone levels. So does the lifestyle changes such as increased exercise, avoiding junk food, and avoiding stressful living.
Adjuvant treatment is required in some cases of testosterone deficiency. These include treatment for erectile dysfunction, insomnia, bone pains, etc.
Nevertheless, the deficiency of testosterone is a treatable disease. The early diagnosis, by looking for signs and symptoms of diseases, has a better prognosis and a decreased incidence of complications.