Sexual function may not be an easy thing to talk about for either the patient or clinician, but it is something that is affected by numerous health conditions. In particular, treatment for prostate cancer can make many men vulnerable to some or total erectile dysfunction which can threaten masculinity, psychological well-being and happy relationships.
The physiology of erectile function
An erection depends on central and peripheral control mechanisms. There are two different types of erection, reflexogenic and psychogenic. In a psychogenic erection the brain is the most important sex organ, as it is erotic stimuli (sight, smell, sound, touch or fantasy) that triggers a response in the hypothalamus. Neurotransmitters are involved in this process, the main ones are dopamine and oxytocin (pro-erectile) and noradrenaline and serotonin (anti-erectile). Reflexogenic erections occur through direct stimulation of the genital organs. The stimuli are transmitted by the dorsal nerve of the penis. The pathway from the spine involves parasympathetic pathway and cavernous nerve involvement.
As well as nerve pathways being involved, there is also a vascular and hormonal response. There is an increase in arterial inflow, smooth muscle relaxes in the intracavernosal sinuses that will fill with blood and expand. Restriction of the venous outflow then allows an erection to occur. Circulating testosterone is important for normal sexual desire and erections (mainly night time erections) and is central acting. Testosterone levels tend to decrease with age.
Understanding the sexual response phases and combining these with the other factors mentioned we start to see how there is an intertwined pathway regarding sexual function, in a four-stage model of sexual response:
- Excitement, sexual arousal develops in response to sexual stimulation. This may not just be physical stimulation but also fantasy. It is the anatomical and physiological response to this stimulation.
- Plateau phase is then achieved if arousal intensifies. It is the stage which precedes the level of arousal necessary to trigger orgasm.
- Orgasmic phase where there is involuntary release of sexual tension. It is where ‘the point of inevitability’ occurs. This is often associated with pleasure and for men, ejaculation
- Resolution is when the bodily changes that occur with arousal return to normal. It is often associated with a sensation of relaxation.
For these four sexual phases to occur the involvement of an intact vascular, nerve and hormonal pathway is required.
The role of the prostate gland
The prostate gland guards the exit to the bladder and is about the size of a walnut and has the same springy consistency as the tip of the nose. The major function of the prostate gland is to produce liquid secretions which contain the glycoprotein prostate – specific antigen (PSA). This liquid mixes with semen which is made in the testes and stored in the seminal vesicles. This process then enables the ejaculatory process to occur.
Erectile dysfunction (ED)
Erectile dysfunction is defined as the inability to achieve an erection suitable for sexual activity and many factors can be involved. These include both physical and psychological issues. Even when there is a significant underlying organic pathology such as radical prostatectomy, cardio vascular disease or diabetes, erectile dysfunction can also be affected by psychological issues. Patients may have complex aetiology.
Health professionals should be proactive in their discussions about sexual function as there is a significant cohort of men who fit in to the categories mentioned above, therefore making it even more important that erectile function is assessed and managed. If a man experiences erectile dysfunction it can be a manifestation of underlying pathology that has not been previously identified such as life threatening cardiac risk. As good practice, erectile dysfunction should be included in every cardiovascular disease risk calculator.
Sex and prostate cancer
In addition to other factors, prostate cancer and its treatment can significantly affect the ejaculatory process. There can be a reduction in ejaculatory volume or total loss of ejaculation. This can have a devastating effect on some men and their partner and the concept of masculinity can be threatened when ejaculation doesn’t occur.
Where pregnancy is desired it is necessary to be very clear with people about this change before treatment and sperm should be saved. If there is any doubt whether there will be a possibility of infertility in the future sperm should be stored.
The nerves that are very close to the prostate gland are necessary in enabling an erection to occur. They can be described as appearing like a ‘spiders web’ which has to be moved away from the prostate when a radical prostatectomy is performed. This can lead to neuropraxia, as the nerves go into a ‘shocked state’ and prevent the link to allow erotic stimuli to trigger an erection as the signal is disrupted from the brain down the spine and to the cavernosal nerves. The high incidence of sudden onset erectile dysfunction following surgery must be addressed. In addition there can also be deterioration of erectile function for men whose treatment options include hormone and radiotherapy and the decline may be over a longer period of time.