Testosterone Deficiency In Men
Testosterone is the primary androgen synthesised and secreted by the testes' Leydig cells in response to the pituitary gland's lutenising hormone (LH). The hormone is controlled by a negative feedback system that includes the pituitary gland and hypothalamus.
The testes produce 5-7mg of testosterone per day, which is converted to the active form, dihydrotestosterone, when it exits the bloodstream and enters target cells.
Approximately 60% of testosterone is bound to the sex hormone binding globulin (SHBG), with the remaining 38% bound by albumin and other proteins. Only about 2% of the testosterone in circulation is free and bioactive.
Normal young men have a circadian rhythm of testosterone release; levels peak around 8 a.m. and drop in the late afternoon/early evening.
After the age of 40, men's testosterone levels gradually but steadily decline by 1-2% each year.
Because SHBG levels rise with age, the level of free, bioactive testosterone declines faster than the level of total testosterone. In elderly men, the circadian rhythm is lost.
Signs and Symptoms
Most men with low testosterone levels are asymptomatic. Men with low testosterone levels may suffer from hypogonadism, which can lead to decreased sex drive and erectile dysfunction.
They may experience a general lack of well-being, depression or anxiety, and difficulty concentrating. They may also notice a reduction in body hair and the need to shave less frequently.
They may also notice an increase in weight as body fat increases and muscle mass decreases. Some men will experience an increase in breast tissue (gynaecomastia).
These symptoms may go unreported because they appear gradually and are accompanied by feelings of embarrassment.
Other manifestations that may not be immediately apparent unless tested for include changes in cholesterol and lipid levels, a decrease in bone mineral density, which leads to osteoporosis and an increased fracture risk, and a decrease in haemoglobin and possible anaemia.
Causes of Low testosterone
Hypogonadism is the clinical condition requiring testosterone replacement, but it is not the most common cause of low testosterone levels. Hypogonadism can be categorised as primary or secondary.
Primary hypogonadism is distinguished by gonad abnormalities, anorchia, or disturbances in testicular function such as undescended testes, testicular inflammation, testicular torsion, or irradiation, in which case luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels are typically elevated. Secondary hypogonadism is caused by insufficient pituitary gonadotrophin (LH/FSH) production, which can be due to pituitary gland failure or hypothalamic defects; such patients may have normal or low LH and FSH levels.
Older men may be diagnosed with "late-onset hypogonadism" (LOH). The condition has been described as "a clinical and biochemical syndrome associated with advancing age and characterised by symptoms and a deficiency in serum testosterone levels" .
Illness and medications
It's important to remember that illness is the most common cause of low testosterone levels. Measurement of testosterone should be avoided during an acute illness, and interpreting a low testosterone level in those with chronic illnesses is difficult.
Before consulting an endocrinologist for diagnosis and treatment, a low testosterone level should be detected on at least two occasions, with samples taken at least four weeks apart.
Many men with type 2 diabetes have low testosterone as a result of their condition; keep this in mind when reviewing their testosterone levels.
Some medications (e.g., opiates, corticosteroids) will also lower testosterone levels, so it is critical to obtain an accurate history from your patient and review their medical records.
Men who use anabolic steroids, as well as those who smoke marijuana or abuse cocaine and methamphetamines, will have lower testosterone levels.
Testosterone levels can be low in shift workers due to a lack of sleep.
Low testosterone is caused by high levels of serum prolactin. High prolactin levels can be caused by hypothyroidism, secretion from a pituitary tumour (prolactinonma), or a variety of medications such as opiates, antipsychotics, antidepressants, and domperidone. Such patients may present with gynecomastia.
This is difficult to quantify accurately because there is no internationally agreed-upon definition of hypogonadism.Men with low testosterone levels may be asymptomatic, so measuring testosterone levels is not the same as measuring symptoms of hypogonadism.
According to the European Male Ageing Study, if testosterone falls below the limit of the reference range for normal young men (-10 nmol/L), the prevalence of biochemical hypogonadism is 23.3% in men aged 40 to 79.
There is no evidence that the prevalence of hypogonadism varies by race or ethnic group.
Diagnosis
This necessitates the demonstration of low testosterone in symptomatic patients.The key symptoms are most closely associated with testosterone levels. Symptoms that provide a less compelling reason to suspect hypogonadism include decreased muscle mass/strength, decreased body hair, osteoporosis gynecomastia, lushing and sweating, simple fatigue, a lack of energy, and depression.
Measuring testosterone
Due to the circadian rhythm of testosterone production, it is critical to obtain a blood sample early in the morning, preferably before 11 a.m.
In shift workers, however, a sample taken before 11 a.m. is invalid.Instead, samples should be collected within four hours of waking.
As previously stated, testosterone levels should be measured on at least two separate occasions, at least a month apart, before beginning any treatment.
Abnormal testosterone results should prompt a request for additional pituitary function tests, including LH, FSH, and prolactin.
Changes in the concentrations of sex hormone-binding globulin (SHBG) and albumin will affect total testosterone levels.
For example, SHBG increases significantly with age and testosterone deficiency but decreases with obesity and type 2 diabetes, so total testosterone levels can be misleading.
