Male Sexual Dysfunction

Male sexual dysfunction is any disorder that interferes with the male sexual response cycle and includes desire disorders, erectile disorders, and ejaculatory disorders. Sexual dysfunction has a varied etiology and may be due to psychological causes, endocrine diseases, neurogenic dysfunction, chronic medical illness, or medication/substance abuse. These disorders often cause significant distress to the patient and sexual partner. Treatment options include psychotherapy, physical therapy, and pharmacotherapy based on the causes of dysfunction.

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Overview

Definition

Male sexual dysfunction is a group of disorders that interfere with any stage of the male’s sexual response cycle and result in disruption of normal sexual function.

Table: Stages of the sexual response cycle
StageChanges in femalesChanges in malesChanges in both
Desire
  • Motivation or interest in sexual activity
  • Expressed by sexual fantasies
Excitement/arousal
  • Begins with either fantasy or physical contact
  • Vaginal lubrication
  • Clitoral erection
  • Labial swelling
  • Elevation of the uterus in the pelvis (tenting)
  • Begins with either fantasy or physical contact
  • Erections and testicular enlargement
  • Flushing
  • Nipple erection
  • Hemodynamic changes (increased respiration, pulse, and BP)
OrgasmVaginal and uterine contractions
  • Tightening of the scrotal sac
  • Secretion of a few drops of seminal fluid
  • Ejaculation
  • Facial grimacing
  • Release of tension
  • Slight clouding of consciousness
  • Involuntary anal sphincter contractions
  • Acute increase in BP and pulse
ResolutionWomen experience little or no refractory period.Men have a refractory period lasting minutes to hours during which they cannot reexperience orgasm.
  • Muscles relax.
  • Cardiovascular state returns to baseline.
  • Sexual organs return to normal baseline.

Epidemiology

  • Decrease in libido: 
    • Affects 5%–15% of men
    • Incidence increases with age.
  • Erectile dysfunction: 
    • Affects 18% of men ages 50–59 years
    • Incidence increases with age.
  • Premature ejaculation: 
    • Most common ejaculatory disorder
    • Estimated prevalence 20%–30%

Normal male sexual function

Normal male sexual function is the result of interaction between multiple systems:

  • Vascular
  • Nervous
  • Hormonal
  • Psychological

Vascular

  • Nitric oxide (NO): 
    • Formed by NO synthase via cyclic guanosine monophosphate (cGMP)–mediated reaction
    • Acts as local neurotransmitter in intracavernosal space to facilitate relaxation of intracavernosal trabeculae
    • Blood flow is maximized, leading to penile engorgement.
  • Decreased intracavernosal NO synthase levels found in: 
    • Cigarette smokers
    • Diabetic patients
    • Testosterone-deficient patients
  • Phosphodiesterase 5 (PDE5) inhibitors (e.g., Viagra) act via a cGMP-dependent mechanism to increase intracavernosal NO.
Penile vascular anatomy

Penile vascular anatomy

Image: “Anatomy, descriptive and applied” by Henry Gray. License: Public Domain

Nervous

Autonomic innervation of male sexual response:

  • Erection:
    • Regulated by parasympathetic system
    • Nerves involved: pelvic splanchnic nerves (S2–S4)
  • Emission:
    • Regulated by sympathetic nervous system
    • Nerve involved: hypogastric nerve (T11–L2)
  • Expulsion:
    • Regulated by visceral and somatic nerves
    • Nerve involved: pudendal nerve

Neural pathways for different types of erections:

  • Psychogenic erections:
    • Stimuli: visual or auditory sexual stimuli
    • Stimuli reach brain → released to spinal cord neural center located at T11–L2 (thoracolumbar erection center)
    • Impulses flow to pelvic vascular bed → blood is redirected into corpora cavernosa/corpus spongiosum 
    • Venous outflow from corpora cavernosa/corpus spongiosum through emissary veins prevented by mass effect of expanded intracavernosal space → maintains erection
    • Common in younger males
  • Reflex erections:
    • Stimuli: tactile stimulus to penis or genital area
    • Stimuli activate reflex arc (sacral roots S2–S4, known as sacral erection center).
    • Common at more mature ages
  • Nonsexual nocturnal erections:
    • Occur during REM sleep (absent in depressed men)
    • Present throughout life

Hormonal

  • Adolescent nocturnal erections: 
    • Gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) → Leydig cell testosterone secretion
  • Testosterone: 
    • Important for libido and NO synthesis
    • Deficiency causes impotence.
    • Sexual potency returns when normalized.
    • Augments psychogenic channels to increase libido
    • Important in maintaining intracavernosal NO synthase levels
  • Hormonal assessment in men with low libido:
    • Testosterone
    • Prolactin
    • Thyroid-stimulating hormone (TSH)
    • Estradiol

Desire Disorder

Features

  • Absence or deficiency of sexual thoughts, desires, or fantasies
  • Duration: ≥ 6 months
  • The disorder causes clinically significant psychological distress.

Risk factors

  • Medications:
    • Selective serotonin reuptake inhibitors (SSRIs)
    • Antiandrogens
    • 5α-reductase inhibitors
    • Opioid analgesics
  • Chronic alcoholism
  • Depression
  • Fatigue
  • Recreational drugs
  • Sexual aversion disorder
  • Systemic illness
  • Testosterone deficiency

Management

  • Risk factor modification
  • Treatment options include:
    • Psychotherapy
    • Testosterone replacement

Erectile Disorder

Features

  • Difficulty obtaining or maintaining erection or decrease in erectile rigidity 
  • Duration: ≥ 6 months
  • The disorder causes clinically significant psychological distress.
  • Also known as erectile dysfunction (ED) or impotence

Risk factors

Table: Risk factors for erectile disorder
Medications
  • Antidepressants (SSRIs)
  • Antipsychotics
  • Sympathetic blockers (clonidine, guanethidine, or methyldopa)
  • Thiazide diuretics
  • Antiandrogenic medications or medications with antiandrogenic activity (e.g., spironolactone, ketoconazole)
Chronic medical conditions
  • Cardiovascular diseases
  • CKD
  • Obstructive sleep apnea
Neurologic conditions
  • Peripheral (autonomic) neuropathy (e.g., diabetic neuropathy)
  • Multiple sclerosis
  • Spinal injuries
Psychogenic conditions (psychogenic ED)
  • Stressors
  • Past related traumatic experience
Endocrine conditions
  • Thyroid disorders
  • Hyperprolactinemia
  • Hypogonadism
ExerciseExtensive bicycling and prolonged pressure on pudendal and cavernosal nerves increase the risk of ED. Regular aerobic exercise not associated with nerve compression decreases the risk of ED.
Penile conditionsPeyronie disease

Management

  • Nonpharmaceutical interventions:
    • Risk factor modification
    • Lifestyle changes
    • Psychotherapy (useful in patients with anxiety) 
  • Pharmaceutical interventions:
    • 1st- line: 
      • PDE5 inhibitors (sildenafil, vardenafil, tadalafil, avanafil)
      • Contraindicated in men taking nitrates (causes hypotension with antihypertensive medications)
    • 2nd-line:
      • Vacuum devices
      • Penile self-injectable drugs (alprostadil)
      • Intraurethral suppositories
      • Penile prosthesis (surgical)
    • Medical treatment of any underlying medical causes
    • Testosterone replacement not recommended as monotherapy for ED
Table: Medications used for erectile disorder
MedicationsMechanism of actionSide effects
  • Sildenafil
  • Vardenafil
  • Tadalafil (longest duration of action)
  • Avanafil (fastest onset of action)
PDE5 inhibitors → increase intracavernosal cGMP → increase intracavernosal NO
  • Hypotension (can happen with any antihypertensive medication)
  • Blue vision discoloration
  • Priapism
  • Flushing, headaches, hearing loss
AlprostadilPGE1 agonist → increase cAMP, decrease Ca2+ → smooth muscle relaxation
  • Injection site reactions or pain
  • Penile discharge
PGE1: prostaglandin E1
Penis enlargement pump

A modern penis pump utilizing a gaiter system in conjunction with water as a penis enlarger or penile rigidity device

Image: “A modern penis pump” by Arctic Sea Limited. License: CC BY 4.0

Ejaculatory Disorders

Features

  • Premature (early) ejaculation: 
    • Ejaculation occurs prior to or within 1 minute after penetration.
    • Inability to delay ejaculation
    • Duration ≥ 6 months
    • Causes clinically significant distress
  • Delayed ejaculation: 
    • Marked delay or absence of ejaculation
    • Duration ≥ 6 months
    • Causes clinically significant distress
  • Retrograde ejaculation:
    • During ejaculation, semen moves in retrograde fashion into bladder rather than exiting urethra.
    • Often occurs following surgery for benign prostatic hyperplasia

Etiology

  • Not well understood
  • Might be related to: 
    • Penile hypersensitivity
    • Genetic predisposing factors
    • Psychogenic factors
    • Medical diseases or surgical complications

Management

  • Psychotherapy
  • Behavioral therapy (stop-and-go technique, squeeze technique)
  • Medications: 
    • SSRIs: 1st-line treatment 
    • Tricyclic antidepressants (TCAs): 2nd-line treatment
    • Tramadol: 3rd-line treatment 
    • Topical anesthetics (with or without systemic therapy)

Clinical Relevance

  • Hypogonadism: medical condition characterized by little or no spontaneous sex hormone production. Hypogonadism may be due to primary causes (e.g., testicular disease) or secondary causes (e.g., pituitary or hypothalamic diseases). This condition is associated with decreased libido, gynecomastia, and testicular atrophy. Diagnosis requires careful assessment and measurement of prolactin level, and MRI might be considered in secondary causes.
  • Peyronie disease: penile condition that presents with palpable plaque and abnormally increased curvature of penis when erect. Peyronie disease is associated with painful erections and/or ED. This disease has a genetic predisposition and might occur because of penile trauma. Treatment includes medical options (vitamin E supplementation, colchicine, tamoxifen, acetyl-L-carnitine, calcium channel blockers) and surgical repair.
  • Sexual physiology: sexual physiology and development begins from early childhood, representing a complex process of events that lead to final development of sexual orientation and behavior. Sexual behavior and interactions include several changes that differ greatly between males and females.
  • Female sexual dysfunction: sexual dysfunction in any part of the sexual response cycle seen in women. Female sexual dysfunction includes desire disorders, arousal disorders, orgasmic disorders, and pain disorders. These disorders may arise from stress and interpersonal conflicts, as well as from physical illness or medication/substance use and can cause significant distress.

References

  1. Ganti L, et al. (2016). Sexual dysfunctions and paraphilic disorders. Chapter 16 of First Aid for the Psychiatry Clerkship, 4th ed., pp. 173–176. McGraw Hill Education.
  2. Wittmann D, Khera M, Trost L, Mulhall J. (2020). Contemporary considerations in the pathophysiology of low sex drive in men. J Sex Med. https://pubmed.ncbi.nlm.nih.gov/32115396/ 
  3. Tsertsvadze A, Fink HA, Yazdi F, et al. (2009). Oral phosphodiesterase-5 inhibitors and hormonal treatments for erectile dysfunction: a systematic review and meta-analysis. Ann Intern Med. https://pubmed.ncbi.nlm.nih.gov/19884626/

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