From the Guidelines
For an 18-year-old male with suspected low testosterone, the primary test to order is a morning total testosterone level, ideally drawn between 8-10 AM when levels are naturally highest, as recommended by the most recent guidelines 1. This should be accompanied by free testosterone measurement, as this represents the biologically active hormone. Additional tests should include luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin to help determine if the issue is primary (testicular) or secondary (pituitary/hypothalamic) 1. A complete blood count, comprehensive metabolic panel, and thyroid function tests are also valuable to rule out other conditions that might affect testosterone. If the initial total testosterone is low (typically below 300 ng/dL), the test should be repeated at least once to confirm the finding, as levels can fluctuate, as suggested by the American Urological Association guidelines 1. Testing should occur when the patient is well-rested and not acutely ill, as illness can temporarily lower testosterone. The patient should avoid strenuous exercise and alcohol for 24 hours before testing. This comprehensive approach helps determine both the presence of hypogonadism and its underlying cause, which is crucial for appropriate treatment in a young male where preservation of fertility may be important. Some key points to consider when evaluating low testosterone in young males include:
- The importance of measuring total testosterone levels on two separate occasions, preferably in the morning, to confirm the diagnosis of hypogonadism 1
- The need to assess for symptoms and signs of hypogonadism, such as decreased libido, erectile dysfunction, and fatigue 1
- The potential benefits of testosterone replacement therapy in men with symptomatic hypogonadism, including improved sexual function, well-being, and bone density 1
From the Research
Diagnosis of Low Testosterone in 18-Year-Old Males
To diagnose low testosterone in an 18-year-old male, the following tests can be ordered:
- Morning testosterone levels on two different occasions to confirm low testosterone levels 2
- Serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels to distinguish between primary (hypergonadotropic) and secondary (hypogonadotropic) hypogonadism 2, 3
Considerations for Young Men
When diagnosing and managing low testosterone in young men, it is essential to consider the underlying etiology and fertility goals 4. The diagnosis of hypogonadism in younger males can be challenging, and symptoms such as low energy are more common than decreased libido or erectile dysfunction 4.
Laboratory Tests
The following laboratory tests can be ordered to diagnose and manage low testosterone in 18-year-old males:
- Testosterone levels: to confirm low testosterone levels 2, 5
- LH and FSH levels: to distinguish between primary and secondary hypogonadism 2, 3
- Bone density tests: to assess the risk of osteoporosis 2, 6
- Hematocrit levels: to monitor for polycythemia 2, 6
Treatment Considerations
When considering treatment for low testosterone in young men, it is crucial to weigh the benefits and risks of testosterone replacement therapy, particularly regarding fertility goals 4, 6. Topical or injectable testosterone therapy can decrease spermatogenesis, posing an infertility risk, and alternative treatments such as intranasal testosterone, selective estrogen modulators, aromatase inhibitors, or human-chorionic gonadotrophin may be preferred 4.