Cause	History	Physical examination	Possible laboratory findings
Vascular	Coronary artery disease; hypertension; laudication; dyslipidemia; smoking	Decreased pulses; bruits; elevated blood pressure; cool extremities	Abnormal lipid profile
			Abnormal penile-brachial pressure index
Diabetes mellitus	Known diabetes; polyuria; polydipsia; polyphagia	Peripheral neuropathy; retinopathy; abnormal body mass index	Abnormal fasting blood glucose
			Elevated glycosylated hemoglobin
			Proteinuria
			Glycosuria
			Hypertriglyceridemia
Hypogonadism	Decreased libido; fatigue	Bilateral testicular atrophy; scant body hair; gynecomastia	Decreased morning free testosterone
			Increased LH
			Increased FSH
Hyperprolactinemia	Decreased libido; galactorrhea; visual complaints; headache	Bitemporal hemianopsia	Elevated prolactin
			Abnormal CT or MRI scans of pituitary gland
Hypothyroidism	Fatigue; cold intolerance	Goiter; myxedema; dry skin; coarse hair	Increased TSH
			Decreased free T4
Hyperthyroidism	Heat intolerance; weight loss; diaphoresis; palpitations	Lid lag; exophthalmos; hyperreflexia; tremor; tachycardia	Decreased TSH
			Increased free T4
Cushing's syndrome	Easy bruising; weight gain; corticosteroid use	Truncal obesity; “moon face”; “buffalo hump”; striae	Elevated overnight dexamethasone suppression test
Alcoholism	Excessive alcohol use; social, economic or occupational consequences of alcohol abuse; withdrawal symptoms	Positive CAGE screen; thin body habitus; palmar erythema; spider telangiectasias; gynecomastia; tremor	Abnormal hepatic transaminases
			Decreased albumin
			Macrocytic anemia
Neurologic	Spinal cord injury; nerve injury (prostate surgery); stroke; peripheral neuropathy; incontinence; multiple sclerosis; Parkinson's disease	Motor or sensory deficits; aphasia; gait abnormality; abnormal bulbocavernosus reflex; tremor
Mechanical	Genital trauma or surgery; Peyronie's disease; congenital abnormalities	Fibrous penile plaques or chordae	None
Psychogenic	Nocturnal erections; sudden onset; history of depression; anhedonia; poor relationship with partner; anxiety; life crisis	Sad or withdrawn affect; tearful; psychomotor retardation	Nocturnal penile tumescence (stamp test; Snap-Gauge)
			Positive depression inventory (Beck's)
Pharmacologic	Inquire about all prescription and nonprescription drugs	See Table 2