What are the causes of low libido in adult males with no specified medical history?

Causes of Low Libido in Men

Low libido in men results from hormonal abnormalities (particularly testosterone deficiency and hyperprolactinemia), chronic medical conditions, medications, psychological factors, and relationship issues—with testosterone deficiency being the most common organic cause requiring biochemical confirmation before treatment. 1, 2

Hormonal Causes

Testosterone Deficiency (Hypogonadism)

• Diminished libido and sense of vitality are hallmark symptoms of hypogonadism, requiring morning total testosterone measurement (drawn 8-10 AM) on two separate occasions, with levels <300 ng/dL confirming the diagnosis. 3, 1, 2
• Primary hypogonadism results from testicular failure (Klinefelter's syndrome, Leydig cell aplasia) with elevated LH/FSH and low testosterone. 3, 1
• Secondary hypogonadism stems from hypothalamic-pituitary dysfunction with low or low-normal LH/FSH and low testosterone, often reversible with treatment. 3, 1, 2
• In men with advanced liver disease, low testosterone results from hypogonadotropic hypogonadism with additional peripheral conversion of androgens to estrogen, and rising sex hormone-binding globulin (SHBG) further reduces free testosterone. 3

Hyperprolactinemia

• Elevated prolactin directly suppresses libido and causes erectile dysfunction independent of testosterone levels, requiring serum prolactin measurement in all men with combined reduced libido and erectile dysfunction. 2
• Hyperprolactinemia is universally present in subjects with reduced libido when this condition exists, necessitating pituitary MRI evaluation for prolactinoma. 2, 4

Other Endocrine Disorders

• Thyroid dysfunction, diabetes mellitus, and hemochromatosis can cause hypogonadism and reduced libido through various mechanisms affecting the hypothalamic-pituitary-gonadal axis. 3

Chronic Medical Conditions

Cardiovascular and Metabolic Disease

• Erectile dysfunction (which commonly co-occurs with low libido) afflicts 52% of men aged 40-70 years and results from psychological, neurological, hormonal, arterial, or cavernosal impairment. 3
• Diabetes mellitus, hypertension, hyperlipidemia, and obesity are strongly associated with sexual dysfunction through vascular and autonomic mechanisms. 3, 5
• Metabolic syndrome components independently contribute to reduced libido and erectile dysfunction. 5

Liver Disease

• In men with advanced liver disease, excess alcohol intake affects the hypothalamic-pituitary axis or directly impairs testicular function, while portosystemic shunting elevates estrogen levels that suppress the hypothalamic-pituitary axis. 3
• Elevated estrogen contributes to erectile dysfunction, oligospermia, testicular atrophy, and feminization in cirrhotic patients. 3

Neurologic Disorders

• Neurogenic sexual dysfunction results from specific neurologic problems including spinal cord injury, autonomic dysfunction (as in diabetes), and various chronic neurologic disorders affecting libido, erection, ejaculation, and orgasm. 6

Medication-Induced Causes

Common Culprit Medications

• Antidepressants and tobacco use are the most common medication and substance causes of erectile dysfunction and reduced libido. 5
• Spironolactone and beta-blockers commonly cause sexual dysfunction through hormonal and autonomic mechanisms. 3
• Medications that alter the hypothalamic-pituitary-gonadal axis include opiates, glucocorticoids, anabolic steroids, and GnRH agonists/antagonists. 3, 2

Substance Use

• Alcohol excess directly affects the hypothalamic-pituitary axis and ovarian/testicular function. 3
• Tobacco, alcohol, and drug use affect spermatogenesis and sexual function through multiple pathways. 3

Psychological and Psychosocial Factors

Primary Psychological Causes

• Dissatisfaction with the relationship or marriage is the most common factor in patients with depressed desire, requiring careful history to distinguish from organic causes. 7
• Performance anxiety and relationship issues are common psychological causes of erectile dysfunction and reduced libido. 5
• Depression, anxiety, and relationship conflict may be primary or secondary contributors requiring thoughtful discussion with patients and partners. 3

Characteristics of Primary Reduced Libido

• Men with primary reduced libido (not associated with hypogonadism, hyperprolactinemia, or psychopathology) are characterized by higher educational attainment, more disturbances in domestic and dyadic relationships, and overall healthier metabolic profiles. 4
• Primary reduced libido patients have lower cardiovascular risk compared to those with secondary reduced libido. 4

Chronic Illness and General Health

Impact of Chronic Disease

• Libido can be decreased in the context of chronic illness and hormonal abnormalities, with sexual dysfunction common in chronic liver disease presenting with impaired arousal, lubrication, orgasm, or satisfaction. 3
• Stress, obesity, and genetic disorders affect sperm quality and production, indirectly impacting sexual function. 3

Occupational and Environmental Factors

• Occupational hazards and exposure to certain hazardous materials may affect fertility and sexual function. 3

Clinical Evaluation Algorithm

When evaluating low libido, measure morning total testosterone (8-10 AM) on two occasions, serum LH/FSH to distinguish primary from secondary hypogonadism, and prolactin levels—particularly when erectile dysfunction coexists. 3, 1, 2

• Check SHBG if total testosterone is borderline, as elevated SHBG reduces bioavailable testosterone causing functional hypogonadism despite normal total testosterone. 2
• Review all medications for drugs suppressing the hypothalamic-pituitary-gonadal axis. 2
• Assess for modifiable factors including obesity (which decreases testosterone and SHBG), smoking, relationship issues, and psychological stressors. 2
• Consider thyroid function testing, screening for diabetes and cardiovascular risk factors, and evaluation for sleep disorders. 3