Contrary to popular belief, low testosterone production is not a common cause of erectile dysfunction (ED), but decreased testosterone production does cause ED. Testosterone replacement therapy (TRT) often improves or completely resolves this condition.

Several behind the scenes functions go into achieving an erection, but unfortunately many diseases (and in some cases their treatment), along with injuries, lifestyle choices, and a variety of physical factors can lead to erectile dysfunction for which proper cause-specific treatment often results in successful resolution.

Low Testosterone is One Cause of Erectile Dysfunction

According to the most contemporary clinical research, and to Jacob Rajfer, MD

and author of the Reviews in Urology published Spring 2000 research article, entitled ‘Relationship Between Testosterone and Erectile Dysfunction’, low testosterone is the rarest of all ED causes.  However, low testosterone is the most common cause endocrine system related erectile dysfunction.  Since it can be difficult to fully understand the complexities of ED apart from at least a cursory knowledge the endocrine system, it is important to provide an overview of this system.

As with several medical terms, endocrine system has its root in the Greek language originating from the two Greek words “endo” meaning inside or within, and “crinis” meaning secrete.  ‘Endocrine system’ is an umbrella term used to describe the extreme complexity of different types of endocrine glands, which are responsible for governing many of the body’s functions.  Comprised of a series of glands that produce chemicals called hormones, the endocrine system wholly or in part regulates sexual functions and reproductive processes, tissue development, metabolism, growth, and mood, and numerous other functions.  Although its mechanisms and effects are very different, the endocrine system is an information signaling system that’s quite similar to the nervous system.  Comparatively, system uses neuropathways as a route and electrical impulses as its messengers, whereas the endocrine glands secrete hormones messengers that travel within bloodstream.  Out of necessity, the nervous system transmits and relays information very quickly with rapid mostly short lived responses, whereas the endocrine system’s effects initiate slowly and deliver prolonged (hours to weeks) responses.

Individual components of the endocrine system include related glands that fall under its command, thereby making up the total network, or system.  Within the human endocrine system the major endocrine organs include the hypothalamus and the pituitary gland.  Additional endocrine glands include the testes, ovaries, adrenals, pancreas, thyroid, and parathyroids.  Technically endocrine organs, which are called glands, secrete hormones into the bloodstream in order to affect the activity of target sites often located in remote bodily regions that far from the site of release. Where said glands are, and how they function can be found below:

• The hypothalamus:  Located within the forebrain (front part of the brain), directly above the pituitary gland, the hypothalamus serves as a command center.  It receives input from other parts of the brain and from peripheral nerves via its neurosecretory cells, which permits it to monitor and adjust the glandular secretion of other system members.

• The pituitary gland:  This tiny organ, the size of a pea, is found at the base of the brain.  Capillaries inside the anterior pituitary gland receive signals (instructions) from the hypothalamus telling it whether or not to secrete specific hormones that are synthesized by this gland.

• The thyroid gland:  This bilobed (divided into two lobes) structure found near the trachea independently synthesizes and secretes three multi-function hormones, namely thyroxine (T4), triiodothyronine (T3), and calcitonin.  The parathyroids consist of four small glands embedded within the thyroid, which produce and secrete parathyroid hormone (PTH) that regulates calcium and phosphorus within the bloodstream.

• The adrenal gland:  Located on top of the kidneys, each adrenal gland is divided into the outer adrenal cortex (produces other hormones necessary for fluid and electrolyte balance known as cortisone and aldosterone) and an inner adrenal medulla (responsible for producing epinephrine and adrenaline/norepinephrine.

• The pancreas:  Located in the abdomen, the pancreas sits in front of the spine above the level of the belly button.  Its two primary functions include 1) making insulin – a hormone that regulates blood sugar levels and second, and 2) making enzymes that help break down proteins.

The last two components of the endocrine system are the male and female sex organs, located in groin area of the body.  The ovaries (in females) primarily produce and secrete sex hormones known as estrogens and progesterone.  The testes (in males) primarily synthesizes and secretes sex hormones known as androgens, such as testosterone.  Secondarily, and as a result of their respective sexual hormone production, both organs are responsible for numerous bodily functions including:  sexual development and function; emotional stability and general sense of well-being; energy levels; sleep patterns and the ability to achieve latter stages of sleep (3, 4, and REM); physical changes both during adolescence and throughout adulthood, along with lean body mass and muscular strength, bone density, body fat percentage, mental faculties like memory and concentration, and bodily/facial/head hair growth.

Erectile dysfunction due to declining serum testosterone levels is generally experienced as men age, a condition known as andropause, but these levels are not usually low enough to cause ED.  However, regardless of the age at which hypogonadism (low testosterone) is suspected of causing ED, the first course of action is typically treatment with TRT – the use of exogenous androgens, also called synthetic testosterone preparations.  If TRT does not prove effective in combating and/or resolving ED within a finite amount of time, then vascular and/or neurologic causes are suspected.  Even men with normal serum testosterone levels may require or request exogenous testosterone therapy when hypogonadic symptoms are present.  This is usually a sign that although still within the normal range, the person’s testosterone levels are below optimal, i.e. less than the optimal range of 700 – 1,100 ng/dl (nanograms per deciliter).  However, as evidenced above the body is highly interrelated and endocrine system problems, especially within one of its subsystems (smaller groups that work together), in particular the one known as HPTA can be another major contributor to erectile dysfunction.  The acronym HPTA stands for the Hypothalamic-Pituitary-Testicular Axis.  Comprised of the hypothalamus, pituitary gland, and testicles this is the specific subsystem or unit of the endocrine system that is responsible for producing the hormone testosterone.  Blunt head trauma, injury, infection, or disease anywhere within upper HPTA sections can cause low testosterone, known as secondary hypothyroidism (low testosterone originating within the (hypothalamus or pituitary gland).  Lower HPTA (within the testes) low testosterone complications, is called primary hypothyroidism.  Lastly, external or non-HPTA related low testosterone complications are referred to as tertiary hypothyroidism.

Other Common Causes of Erectile Dysfunction 

A lot behind the curtain functions and conditions go into achieving an erection, which effectively starts with stimulation, the firing of nerves in brain which travel down the spinal cord to the penis where muscles are relaxed, and blood vessels become engorged resulting in a rigid erection.  However, a variety of conditions, diseases, medications, physical factors, injuries, personal habits can and quite often do cause erectile dysfunction.

Treatments for ED are extremely successful but, finding the correct cause is central to resolution.  The most common physical, or not disease-related potential causes include:

• Venous leak:  Once an erection has been achieved, in order to sustain it the blood that flows into the penis must stay in the penis.  When said blood flows back out too quickly it is referred to as a condition known as venous leak.  More specifically, the veins within the penis fail to properly constrict causing the erection to subside.  This condition can be caused by both injuries and diseases.

• Prostate enlargement:  The prostate is situated between the lower (exiting) opening of the bladder and the upper (entering) opening of the urethra.  When an enlarged prostate constricts the urethra it usually causes various urinary problems, but in some cases can also hinder erectile efficiency.

• Injuries:  Head trauma which injures the brain, more specifically the hypothalamus and/or pituitary gland (two important components of the reproductive system), or injuries to spinal cord (along which signals from the brain the testes are sent), the testicles themselves, the pelvis, the bladder, or the penis can all greatly induce erectile dysfunction and may require surgical repair.

• Drug use (tobacco, alcohol, etc.):  Some types of drugs possess the potential to damage penile blood vessels or their smaller counterparts the capillaries, making it difficult for erection sustaining blood flow to reach and/or stay in the penis throughout satisfactory intercourse.  Furthermore, research has been found that hardening of the arteries (arteriosclerosis), which can be caused by smoking also raises the risk potential for developing erectile dysfunction.

• Prescription medications:  Even beneficial, prescribed medications (which are still drugs) can cause ED.  Currently more than 200 prescription medications have been clinically proven to cause or increase the risk of ED.

• Surgery:  Surgery for both prostate cancer and bladder cancer can damage the nerves and tissues necessary for an erection. Sometimes the problem resolves on its own, usually within 6 to 18 months, but this type of damage can also be permanent.  Should permanent damage occurs, specific treatments exist to help restore the ability to achieve and sustain an erection.

• Hormonal imbalances:  Although testosterone is central, it and a variety of other hormones work together to support a man’s libido or sex drive.  An imbalance in such hormones can diminish sexual interest.  Conditions at the top of list for most common hormonal imbalance causes are kidney and liver disease, pituitary gland tumors, hormone treatment of prostate cancer, and depression.

Diseases represent yet another group of erectile dysfunction promoting conditions.  The most common causes of disease-related ED include:

• Prostate cancer:  This type of cancer doesn’t cause ED, but temporary or permanent erectile dysfunction can be caused by its treatments.

• Vascular diseases:  Certain diseases can block blood vessels, which slows the flow of blood to the penis, thereby making it difficult to achieve an erection.  Among the most common causes of ED is the hardening of the arteries disease known as atherosclerosis, which also promotes high blood pressure, and high cholesterol levels.

• Neurological (nerve and brain) disorders:  It is not possible to achieve an erection without the nervous system, which transmits both sexual stimulation (from various erogenous zones) to the brain and commands from the brain to the penis.  Strokes and diseases which disrupt these neurological signals such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis can lead to ED.

• Diabetes:  This chronic disease increases the risk of, and can actually damage the nerves and blood vessels that aid in achieving erection.  Diabetes is such a problem in its relation to hypogonadism that if not properly controlled, some studies have shown that it can literally double a man’s risk of erectile dysfunction.
• Kidney disease:  This condition can affect many of the components required for a healthy erection including nourishing blood flow to the penis, hormonal secretion levels, and specifically integral parts of the nervous system. Additionally, kidney disease and many of the medications used to treat it may cause the body to more easily fatigue thereby diminishing energy levels, which can also promote reduced libido.

Low testosterone levels, problems within the endocrine system, disease related, and non-disease related conditions can independently or collectively contribute to erectile dysfunction.  This large number of possible problems can make erectile dysfunction a very complex condition, for which determining cause is the most important part of successful resolution.  Nevertheless, endocrinologists are very good at locating ED causes, and the outlook for both low testosterone and non-low testosterone erectile dysfunction is quite good when proper medical care is received.

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