Laboratory Evaluations for Erectile Dysfunction
For patients presenting with erectile dysfunction, essential laboratory tests include morning serum total testosterone, fasting glucose/HbA1c, and lipid profile, with additional specialized testing based on clinical presentation. 1, 2
Core Laboratory Testing
- Morning serum total testosterone should be measured in all men with erectile dysfunction to evaluate for testosterone deficiency (defined as <300 ng/dL with symptoms) 1
- Fasting glucose and/or HbA1c should be obtained to screen for diabetes, as ED may be the first presenting symptom of diabetes 2, 3
- Lipid profile (total cholesterol, HDL, LDL, triglycerides) should be measured to assess cardiovascular risk factors 2, 4
- With the exception of these tests, no other routine serum studies are likely to alter ED management 1
Clinical Context for Laboratory Testing
- ED is a significant risk marker for underlying cardiovascular disease and other health conditions that warrant evaluation and treatment 1
- Laboratory results should be interpreted alongside a thorough medical, sexual, and psychosocial history 1
- Validated questionnaires such as the Sexual Health Inventory for Men or Erection Hardness Score should be used in conjunction with laboratory testing to assess ED severity 1, 2
Additional Testing Based on Clinical Presentation
- If initial testosterone level is low, repeat measurement is recommended along with luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin to identify potential endocrine disorders 5, 6
- Prolactin should be measured when testosterone levels are diminished or when hypogonadism is suspected 2, 6
- For patients who may receive testosterone replacement therapy, baseline prostate-specific antigen (PSA) measurement should be considered 2
Important Clinical Considerations
- Testosterone levels should be measured in the morning due to diurnal variation 2
- In patients with normal fasting glucose but risk factors for diabetes, an oral glucose tolerance test may uncover undiagnosed diabetes (present in up to 12.1% of ED patients with normal fasting glucose) 3
- Free or bioavailable testosterone may be preferred over total testosterone when hypogonadism is suspected based on history or examination 2
Common Pitfalls to Avoid
- Failing to measure testosterone levels in the morning can lead to falsely low results due to diurnal variation 2
- Overlooking ED as a potential early marker of cardiovascular disease or diabetes can miss opportunities for early intervention 1, 3
- Not repeating abnormal testosterone measurements before initiating treatment can lead to unnecessary therapy 5
- Neglecting to consider medication side effects as a cause of ED during laboratory evaluation 7