Endocrinological Causes of Erectile Dysfunction 

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Endocrine disorders as a cause of erectile dysfunction fall into three groups: diabetes mellitus, higher than normal prolactin levels (hyperprolactinemia), and low testosterone levels which causes decreased libido and secondary erectile dysfunction.

Diabetes is the primary cause of male erectile dysfunction, and is said to be responsible for about four cases in ten.

The other hormonal (endocrinological) causes listed above are much less common, at least in conventional thinking, though the importance of low testosterone levels in the onset of erectile dysfunction may not have been fully recognized.

Fortunately, these cases of erectile dysfunction can easily be treated and there is often a rapid improvement in erectile capacity. Diabetes as a cause of erectile dysfunction

Diabetes mellitus is a disease which involves problems with the metabolism of glucose. This means, in simple terms, that the body cannot process  sugar-type compounds in food.

There are several side-effects and long-term complications to which diabetic men and women may be susceptible: we shall look at these in a moment. There are two forms of diabetes: Type 1, or insulin-dependent, and Type 11 or non-insulin-dependent.

Both forms cause small-vessel disease, which may affect the retina, the heart, and the  cerebrovascular vessels supplying the brain with blood. Men and women with either type of diabetes are also susceptible to peripheral neuropathy - i.e. nerve damage.

Erectile dysfunction in most diabetics is due to long-term complications which are associated with both small-vessel disease and nerve neuropathy.

Between one third and two thirds of diabetic men will develop erectile dysfunction as a consequence of these problems. If a diabetic man has peripheral nerve damage and other issues associated with it, such as lower limb numbness or pain, it's most likely that he will already have erectile dysfunction.

Of course, it is still possible for a diabetic man to have erectile dysfunction caused primarily by psychological problems.

As you would expect, the stress of diabetes and erectile dysfunction is mutually reinforcing, particularly in under 40, so they may well suffer from anxiety and depression: again, we face the issue of which emotion is cause and which is effect?

And, although diabetics routinely develop erectile dysfunction, the progress of the disease can be slow, and the best way to control its progression is to ensure strict control of blood sugar levels.

 Diabetic men with developing erectile dysfunction can be offered the same treatment strategies as non-diabetic men with erectile dysfunction: psychotherapy, Viagra, even drugs injected or placed in the urethra.


Prolactin is the hormone that causes milk production in lactating women, but in men it has no function when it is at normal levels. If for any reason, levels become excessive levels (a condition known as hyperprolactinemia), it decreases sex drive and can indirectly induce erectile dysfunction.

Men with higher than normal levels of prolactin will be investigated by a specialist for any possible causes of their elevated prolactin, including medication, prolactin secreting tumors, and idiopathic hyperprolactinemia. Idiopathic hyperprolactinernia is treated with drugs, while prolactinomas sometimes require surgery and radiation therapy.

 Alternatively, medical therapy is using Bromocriptine can be highly effective. Using this therapy, the time taken to reduce the size of the tumor and for the return of testosterone can be between six and twelve months.

In summary, therefore, diabetes mellitus appears to be the most common disorder behind erectile dysfunction, which it causes by its impact on both the neurologic function and the integrity of the blood vessels which are needed for a normal erection.

Up to about half of all men with diabetes will develop some degree of erectile dysfunction, which will best be managed by early diagnosis, effective monitoring, and good control of blood sugars.

Diabetic men normally have a lot of performance anxiety around erectile dysfunction; so just because a man's diabetic one can't assume his erectile dysfunction is a product of his diabetes. Indeed, a diabetic man needs to be questioned very carefully about his  psychosexual history to establish if his problem is primarily physical or primarily psychological.

Hyperprolactinerma (elevated blood levels of prolactin) is another common hormonal factor in erectile dysfunction. Increased prolactin levels cause a significant decrease in sex drive and a decrease in blood serum testosterone levels.

So men with decreased libido or low testosterone levels require measurement of their prolactin levels. A large number of illnesses and medications can play a part in the elevation of d blood prolactin levels.

The physiology of penile erection

An erection requires an effective and functioning combination of vascular, neuronal, and hormonal factors.

During sexual stimulation, neurotransmitters flow from the nerve terminals in the corpora cavernosa,  vasoactive relaxing factors are released from the cells of the endothelium lining the penile blood vessels.

This in turn causes the relaxation of the smooth muscles associated with the arterial system which supplies blood to the erectile tissue; this causes a significant increase in blood flow into the penis.

At the same time, the trabecular smooth muscle relaxes, and this causes an increase in the volume of the sinusoids followed by inflow of blood, rapid filling and consequent expansion of the sinusoidal system.

At the same time, the veins of the  subtunical layers are compressed, and there is an almost complete occlusion of these veins, preventing blood outflow. This combination of inflow and reduced outflow causes the penis to become erect.

Nitric oxide is the primary neurotransmitter associated with erection. High levels of nitric oxide inside the penis are associated with the relaxation of intracavernosal trabeculae, the process which results in high inward blood flow and the development of erection. Nonadrenergic, noncholinergic neurons release nitric oxide, and this leads to an increase in the cellular production of cyclic guanosine monophosphate.

In turn, cGMP is able to activate a specific protein kinase, and this phosphorylates specific proteins and ion channels; as a result, the intracellular potassium channels open and there is a hyperpolarization of the muscle-cell membrane, followed by sequestration of intracellular calcium by the endo plasmic reticulum, and lastly the blocking of calcium influx mediated by the inhibition of membrane calcium channels.

The overall effect is a reduction in cytosolic calcium levels and the relaxation of the smooth muscle of the penis. The reverse process, erection to flaccidity, involves the hydrolysis of cGMP to the compund guanosine monophosphate mediated by phosphodiesterase type 5.

Other vasoactive compounds are involved in the mechanism of erection, including vasoactive intestinal polypeptide, neuro peptide Y, calcitonin gene related peptide, and serotonin.

The role of testosterone in the mechanism of erection is not yet fully clear.

Hypogonadal men usually experience a significant lowering of libido, but the mechanism of erection seems to need a lower concentration of testosterone than one would normally find in a man's blood; some authorities assert that there is no correlation between serum testosterone and the level of erectile dysfunction, though androgens may be needed for correct functioning of the nitric oxide metabolic pathway.

Certainly, testosterone is needed to maintain the levels of intrapenile nitric oxide synthase, and these possibly mediate local vasodilation of blood vessels by increased production of nitric oxide.