Low testosterone (low-T) facts
- Low testosterone is a term used by physicians to describe below normal levels of the hormone testosterone in individuals.
- Symptoms of low testosterone include erectile dysfunction in men as the most common symptom; there are many other symptoms that can occur in both men and women (for example, low sex drive, bone and muscle tissue loss, depression).
- Causes of low-T are numerous; some are classified into primary, secondary or tertiary causes while others are due to underlying diseases or conditions and/or lifestyle factors.
- Medical care should be sought for symptoms of low-T.
- Low-T is presumptively diagnosed by clinical signs and symptoms; definitive diagnosis is usually done in adult males by a blood test that determines testosterone levels.
- Treatment in males is done by prescribing testosterone shots or testosterone that can be adsorbed topically through the skin or gums.
- The complications of low-T are many and include erectile dysfunction, depression, bone density loss, muscle loss, and many others.
- The outlook for patients with low-T may range from good to poor, depending on a individual's sex, age, and response to treatment.
- Low-T cannot be prevented in some individuals usually because of genetic or underlying diseases; however, in other individuals, low-T can be prevented or delayed by lifestyle changes and choices.
What is low testosterone (low-T)?
Low testosterone is a term used by doctors to describe an abnormal level of the hormone testosterone. When appropriately measured, low testosterone is considered to be below 300 ng/dl in male patients, although some doctors suggest the normal range is 270 – 1070 ng/dl. Other terms for low-T include hypogonadism (primary, secondary and tertiary, depending on the cause of low-T) and testosterone deficiency (TD).
Testosterone is a steroid hormone produced in the adrenal glands of both sexes and in the testes of males and the ovaries of females. Testosterone is largely responsible for the formation and maintenance of male sex characteristics, including both the larger bone and muscle development seen in males. The testosterone levels in humans are regulated by hormones released from the brain; in males the hypothalamus and pituitary glands in the brain increase testosterone during puberty and male characteristics develop (for example, penile enlargement, facial hair, interest in sex).
Although the large majority of low testosterone problems centers on adult males, low-T is not confined to male adults. However, the definition and characterization of low-T in women is less clear than for adult men.
Testosterone production is part of the body's endocrine system.
Illustration of the Endocrine System
What causes low testosterone?
The causes of low-T are many and can be separated into three categories: primary, secondary, and tertiary.
Primary types of low-T or primary hypogonadism refer to the injury or failure of organs that are the main producers of testosterone, the testes and ovaries. Causes of primary low-T include scrotal or testicle injuries, undescended testicles, mumps, orchitis, chemotherapy or radiation therapy, chromosomal abnormalities, ovarian failure or surgical removal, and aging.
Causes of secondary low-T or secondary hypogonadism are related to the pituitary gland regulation of testosterone, while tertiary low-T or tertiary hypogonadism is related to the hypothalamus (a gland within the brain that regulates the pituitary and other glands) regulation of testosterone. Most causes of secondary and tertiary low-T are the same for the pituitary and hypothalamus; in addition, the causes may affect both at the same time. Causes of secondary and tertiary low-T include:
- Tumors associated with the pituitary or hypothalamus
- Chemotherapy of nearby tumors
- Gland malformations
- Decreased blood flow to glands for any reason
- Gland inflammation due to disease (HIV, tuberculosis, sarcoidosis)
- Taking anabolic steroids to enhance performance or muscle mass (athletes, body builders)
There are other causes that reduce testosterone that do not fit well into the above categories. Most notable is obesity, in which fat cells enhance conversion of testosterone to estrogen. Diseases such as diabetes, renal disease, COPD, high blood pressure, and lifestyles that include smoking and drug abuse also contribute to low-T.
Other less frequent causes are modified cell receptors for testosterone and unusual cell mechanisms that are rarely identified.
What are the symptoms of low testosterone?
There are many signs and symptoms of low-T. The most common sign and symptoms that bring males to their doctors is erectile dysfunction (poor or no erection of the penis). However, there are many other signs and symptoms that also may occur:
- Reduced sex drive
- Reduced or absent orgasm
- Reduced or absent spontaneous erections
- Loss or reduction of pubic, armpit, or facial hair
- Size reduction of testes
- Breast discomfort or enlargement
- Hot flashes or sweating
- Reduction in strength
- Sleep disturbances
- Memory reduction
Other signs may be seen in examination or tests done by a doctor
Many of the above may be see in women with low-T except for the male specific symptoms.
When should a person seek medical care for low testosterone?
A person should seek medical care if they notice any of the symptoms (as previously discussed) that are associated with low-T. Males that have erectile dysfunction should seek medical care and not rely on medications or cures advertised on TV or the internet, or from anywhere else to self-treat the problem.
Females who have symptoms should discuss them with their OB/GYN doctor or an endocrinologist.
How is low testosterone diagnosed?
Low-T is presumptively diagnosed by the person's history of signs and symptoms (see low-T symptoms previously) and by physical examination.
For males, a blood test is available that can detect testosterone levels and provides the basis for a definitive diagnosis for low-T. Normal values vary from 270 – 1070 ng/dl but the definition of "normal" varies slightly according to different experts. Most blood test measurements are done in the morning because that is when the daily production of testosterone in males is highest.
Blood tests for females are more variable in results (some researchers suggest females have about one-third to one-eighth the male level of testosterone) so the diagnosis is more difficult and often based on symptoms and physical findings.
In addition, other tests (blood, imaging) may be done to diagnose if the low-T has secondary or tertiary causes or if underlying diseases are contributing to symptom development or inhibiting testosterone production.
What is the treatment for low testosterone?
In males, the treatment for low-T is based on two approaches.
- If there are underlying causes for low-T (for example, HIV, tumors, chemotherapy, diabetes, obesity), the doctor should begin individualized treatment for these underlying causes.
- The low-T levels can be supplemented by hormones prescribed by a doctor. Expert recommendations vary on when to treat with hormones; some suggest treatment if levels are at 300ng/dl while others recommend starting treatment if levels are at 230 ng/dl. Although researchers suggest about 70% of men aged 70 and above have low-T, some researchers suggest that hormone treatment may not be effective in this age group. However, when prescribed, hormone therapy (testosterone) can be given in an injection, pellet implant, on a skin patch, in a gel put on the skin, or as an oral gel or putty applied to the gums.
In the US, there is no FDA approved method for testosterone replacement in females. However, some doctors may still prescribe some form of testosterone to females, but the efficacy and safety of this treatment has not been proven.
Use of topical hormones should be done with care. Women should not come in contact with the skin area treated with the absorbable testosterone as the hormone may be absorbed through their skin, too. This could cause women to develop male characteristics.
What are complications of low testosterone?
Complications of low-T vary among individuals. For adult males, the most common symptom of erectile dysfunction can lead to stress, depression, or marital discord and low sex drive and except for penile erectile dysfunction; similar complications can occur in women. In addition, muscle mass, bone density, and fertility may be reduced.
Recent studies suggest a link between testosterone therapy and an increased risk in heart disease. For example, a 2014 study reported that testosterone therapy might increase the risk of a heart attack in men aged 65 and older, as well as in younger men who have a history of heart disease. The use of testosterone should be discussed with your physician.
What is the outlook (prognosis) for a person with low testosterone?
In adult males, the outlook for a patient with low-T may range from good to fair; depending on the person's response to treatment and their age (older patients may not respond as well to treatment). Those patients diagnosed and treated late in the disease process may suffer muscle loss and osteoporosis.
The prognosis for women is less clear; until a treatment protocol and/or drug is approved by the FDA, testosterone treatments will depend on individually designed off-label or experimental protocols for each female and her doctor(s).
How is low testosterone prevented?
Low-T that is caused by genetic factors cannot be prevented, nor can low-T be prevented if the underlying cause is a disease caused by inherited genetic factors or necessary treatments such as chemotherapy. However, some causes that can result in low-T such as obesity, smoking, and drug abuse may be avoided by changing a person's lifestyle. These changes may prevent or delay the onset of low-T. In addition, early diagnosis and treatment may prevent muscle and bone loss.