What are the possible causes of a sudden loss of nocturnal penile tumescence and libido in an adult male?

Sudden Loss of Morning Erections and Sex Drive: Causes and Evaluation

The sudden loss of both morning erections and libido most likely indicates testosterone deficiency or depression, and requires immediate measurement of morning serum total testosterone along with screening for psychological factors. 1, 2

Key Diagnostic Indicators

The combination of these two symptoms is highly specific:

• Loss of libido specifically points toward testosterone deficiency or depression, distinguishing this presentation from isolated erectile dysfunction 2
• Decreased spontaneous/morning erections is one of the three most specific sexual symptoms of late-onset hypogonadism, along with reduced libido and erectile dysfunction 1
• The sudden onset pattern suggests either an acute hormonal change or a psychogenic trigger (such as depression, anxiety, or relationship conflict), whereas gradual onset would indicate progressive organic disease 3, 2

Immediate Evaluation Required

Mandatory Laboratory Testing

• Measure morning serum total testosterone (drawn between 8-10 AM) immediately—this is non-negotiable for any man presenting with loss of libido and morning erections 1, 3, 2
• Testosterone deficiency is defined as total testosterone <300 ng/dL with compatible symptoms 1, 2
• If the initial testosterone is low, repeat the measurement to confirm before initiating treatment 2

Essential History Components

• Ask specifically about preserved erections during masturbation—if present, this suggests a psychogenic component rather than pure organic dysfunction 3, 2
• Screen for depression, anxiety, recent life stressors, and relationship conflicts, as these are common causes of sudden sexual dysfunction 1, 3, 2
• Review all medications systematically—antidepressants (SSRIs, TCAs), antihypertensives (beta-blockers, diuretics), antipsychotics, and finasteride can all cause both decreased libido and erectile dysfunction 3, 2, 4
• Quantify alcohol consumption—heavy use directly causes both symptoms 3

Additional Baseline Testing

• Obtain fasting glucose or HbA1c to screen for diabetes mellitus 3, 2
• Order a fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) 3, 2
• Measure blood pressure as part of cardiovascular risk assessment 2

Common Causes by Category

Endocrine Disorders

• Testosterone deficiency (hypogonadism) is the most likely hormonal cause when both libido and morning erections are lost 1, 2, 5
• Hyperprolactinemia (prolactin >35 ng/mL) suppresses testosterone production and directly impairs sexual desire—check prolactin if testosterone is low 1, 6
• Hypothyroidism mainly affects sexual desire and can impair erectile function, though less commonly than hypogonadism 7, 6
• Hyperthyroidism is associated with erectile dysfunction and ejaculatory problems 6
• Diabetes mellitus causes multifactorial erectile dysfunction through vascular and neurological complications 7, 8

Medication-Induced Causes

• Finasteride and dutasteride (5α-reductase inhibitors) cause decreased libido (6.4% in year 1), impotence (8.1%), and decreased ejaculate volume; sexual dysfunction can persist even after discontinuation 4
• Antidepressants (especially SSRIs) are among the most common medication causes of both decreased libido and erectile dysfunction 3, 8
• Antihypertensives (beta-blockers, thiazide diuretics) frequently cause erectile dysfunction 3
• Antiandrogens (cyproterone acetate, spironolactone, bicalutamide) directly block androgen receptors 1

Psychological Factors

• Depression causes both loss of libido and erectile dysfunction; it must be addressed before or alongside sexual dysfunction treatment 1, 3, 2
• Performance anxiety and relationship conflict can cause sudden onset of symptoms, especially if morning/masturbatory erections are preserved 1, 3
• Recent major life stressors (job loss, bereavement, trauma) can trigger acute sexual dysfunction 3, 2

Vascular and Metabolic Factors

• Obesity, hyperlipidemia, and metabolic syndrome decrease sex hormone-binding globulin (SHBG) and contribute to erectile dysfunction 1, 8
• Cardiovascular disease is both a cause and consequence of erectile dysfunction—ED predicts future cardiac events as strongly as smoking 1, 3, 2

Treatment Algorithm

If Testosterone Deficiency Is Confirmed

• Initiate testosterone replacement therapy in men with total testosterone <300 ng/dL plus symptoms—this improves both libido and erectile function 2, 5
• Testosterone therapy enhances response to PDE5 inhibitors when used concurrently 2
• Before starting testosterone, obtain baseline hemoglobin/hematocrit and PSA (in men >40 years) 2
• Withhold testosterone if hematocrit >50%; reduce dose or stop if it rises above 54% on treatment 2

If Depression or Psychological Factors Are Present

• Refer to a mental health professional for psychotherapy and psychosexual counseling as first-line therapy 1, 3, 2
• Address the underlying psychiatric condition before or alongside ED treatment—antidepressants themselves may worsen sexual function 2
• Involve the sexual partner in counseling when possible to optimize outcomes 1

Pharmacologic Treatment

• Prescribe a PDE5 inhibitor (sildenafil, tadalafil, vardenafil, or avanafil) as first-line therapy regardless of whether the cause is organic, psychogenic, or mixed 1, 3, 2
• Combining PDE5 inhibitors with psychosexual counseling yields superior outcomes compared to either alone 3, 2
• Ensure adequate testosterone levels before or during PDE5 inhibitor therapy, as low testosterone diminishes drug efficacy 2
• Educate patients that sexual stimulation is required for PDE5 inhibitors to work and that at least 5 attempts at maximum dose should be made before declaring treatment failure 1, 2

Lifestyle Modifications (For All Patients)

• Advise complete smoking cessation 3, 2
• Target BMI <30 kg/m² through weight loss 3, 2
• Encourage regular aerobic exercise 2
• Limit alcohol to ≤14 units per week 3, 2
• Optimize control of diabetes, hypertension, and hyperlipidemia 3, 2

Critical Pitfalls to Avoid

• Do not delay testosterone testing when loss of libido is reported—the combination of sudden ED with decreased libido makes testosterone deficiency highly likely and treatable 2
• Do not assume purely psychogenic ED requires only counseling—PDE5 inhibitors work for both psychogenic and organic ED and should be initiated concurrently with psychological therapy 2
• Do not treat ED without addressing cardiovascular risk—men with organic ED should be considered at increased cardiovascular disease risk until proven otherwise 1, 3, 2
• Do not prescribe testosterone replacement unless hypogonadism is documented (total testosterone <300 ng/dL with symptoms) 2
• Do not overlook medication review—many commonly prescribed drugs cause sexual dysfunction and may need adjustment or substitution 3, 2
• Do not initiate ED treatment before addressing alcohol dependence if heavy use is identified 3