Recommended Laboratory Tests for Erectile Dysfunction
Routine laboratory tests for patients presenting with erectile dysfunction should include HbA1c, fasting blood glucose, lipid profile, and morning serum total testosterone levels. 1
Core Laboratory Testing
- HbA1c and fasting blood glucose should be measured to screen for diabetes, as ED is commonly associated with diabetes and may be the first presenting symptom 1
- Lipid profile (total cholesterol, HDL, LDL, triglycerides) should be obtained to assess cardiovascular risk factors 1, 2
- Morning serum total testosterone is essential to evaluate for testosterone deficiency (defined as <300 ng/dL with symptoms) 1
- If hypogonadism is suspected based on history or examination, free testosterone or bioavailable testosterone is preferred over total testosterone 1
Additional Testing Based on Clinical Presentation
- Prostate-specific antigen (PSA) and digital rectal examination should be performed as baseline measurements in patients who may receive testosterone replacement therapy 1
- Triglyceride-Glucose Index (TyG) calculation may be valuable as it has been shown to be an independent predictor of ED (cutoff value of 8.88) 3
- Fasting insulin levels may be considered to assess insulin resistance, which is strongly associated with ED 3, 4
Specialized Testing for Select Patients
- For patients who do not respond to first-line therapies, additional testing may include 1:
- Nocturnal penile tumescence and rigidity assessment
- Penile Doppler ultrasound (particularly valuable in patients with metabolic syndrome) 4
- Bulbo-cavernosus reflex testing
- Dorsal sensory nerve conduction studies
- Pudendal nerve somatosensory evoked potentials
Clinical Considerations
- ED is a risk marker for underlying cardiovascular disease and other health conditions that warrant evaluation 1
- In patients with normal fasting glucose, an oral glucose tolerance test may be valuable as 12.1% of ED patients with normal fasting glucose have undiagnosed diabetes mellitus 5
- Laboratory testing should be interpreted in conjunction with a thorough medical, sexual, and psychosocial history 1, 6
- Validated questionnaires such as the International Index of Erectile Function (IIEF) should be used alongside laboratory testing to assess ED severity 1
Potential Pitfalls
- Testosterone levels should be measured in the morning due to diurnal variation 1
- A single normal laboratory result does not exclude pathology; consider repeat testing if clinical suspicion remains high 6
- Failure to screen for cardiovascular risk factors may miss an opportunity for early intervention, as ED can precede clinical cardiovascular disease 2, 5
- Not all ED is organic; laboratory testing should be interpreted in the context of the patient's psychological and relationship factors 1, 6