Why Testosterone Panel Blood Tests Are Performed
Testosterone panel blood tests are performed to diagnose testosterone deficiency (hypogonadism) in patients presenting with specific symptoms—particularly diminished libido and erectile dysfunction—and to identify high-risk patients who warrant screening even without symptoms. 1
Primary Diagnostic Purpose
The core reason for ordering testosterone panels is to establish a biochemical diagnosis of hypogonadism, which requires both low testosterone measurements and clinical symptoms. 1 The diagnosis cannot be made on symptoms alone, nor can it be made on a single laboratory value. 1
Required Testing Protocol
- Two separate morning testosterone measurements (drawn between 8-10 AM) showing levels consistently below 300 ng/dL are required to diagnose testosterone deficiency. 1, 2
- Morning timing is critical because testosterone levels fluctuate throughout the day, with peak levels occurring in early morning. 1, 3
- Both measurements should ideally use the same laboratory and methodology to minimize assay variability. 1
Key Symptoms Warranting Testing
Testosterone panels should be ordered when patients report: 1, 2
- Reduced libido (decreased sex drive)
- Erectile dysfunction, particularly when PDE5 inhibitor therapy has failed 2, 4
- Reduced energy and endurance
- Diminished work or physical performance
- Fatigue
- Depression or reduced motivation
- Poor concentration or impaired memory
- Infertility 1
High-Risk Populations Requiring Screening
Even in the absence of symptoms, testosterone measurement is recommended for patients with specific medical conditions that increase hypogonadism risk: 1, 2
- Unexplained anemia
- Bone density loss or osteoporosis
- Diabetes mellitus
- Exposure to chemotherapy
- Direct or scatter testicular radiation
- HIV/AIDS
- Chronic narcotic use
- Male infertility
- Pituitary dysfunction
- Chronic corticosteroid use 1, 2
Beyond Total Testosterone: When Additional Testing Is Needed
Free Testosterone Measurement
Total testosterone alone can miss up to 17-26% of hypogonadism cases, particularly in older men and those with obesity. 5, 6 This occurs because:
- Elevated sex hormone-binding globulin (SHBG) can bind testosterone, creating falsely reassuring total testosterone levels while free (bioavailable) testosterone remains low. 5, 6
- In men over 60 years presenting with erectile dysfunction, 26.3% have normal total testosterone but low free testosterone. 5
- Free testosterone by equilibrium dialysis should be measured when total testosterone is borderline (231-346 ng/dL) or in patients with obesity, diabetes, or advanced age. 3, 4, 6
Distinguishing Primary from Secondary Hypogonadism
Once low testosterone is confirmed, measuring LH and FSH is mandatory to determine the type of hypogonadism: 1, 7
- Elevated LH/FSH with low testosterone = primary (testicular) hypogonadism
- Low or inappropriately normal LH/FSH with low testosterone = secondary (hypothalamic-pituitary) hypogonadism 7
This distinction has critical treatment implications: 7
- Men with secondary hypogonadism who desire fertility must receive gonadotropin therapy (hCG plus FSH), not testosterone replacement, as testosterone will cause azoospermia. 2, 3, 7
- Skipping this testing can lead to inappropriate treatment that permanently compromises fertility. 7
Additional Workup for Secondary Hypogonadism
When secondary hypogonadism is identified (low testosterone with low/normal LH and FSH): 7
- Serum prolactin must be measured to screen for hyperprolactinemia or prolactinomas. 7
- Pituitary MRI should be considered if testosterone is <150 ng/dL, as non-secreting adenomas may be present. 7
Common Pitfalls in Testosterone Testing
The Problem of Inappropriate Testing and Treatment
Approximately 20-30% of men receiving testosterone therapy in the United States do not have documented low testosterone levels before treatment initiation. 1, 2 This represents a significant practice pattern violation of evidence-based guidelines. 2
Furthermore: 1
- Nearly half of men on testosterone therapy never have their levels checked after treatment begins
- Up to one-third of men placed on testosterone do not meet diagnostic criteria for testosterone deficiency
Screening Questionnaires Are Not Sufficient
Validated questionnaires should not be used to diagnose testosterone deficiency or identify candidates for therapy. 1 Symptoms alone lack specificity, and biochemical confirmation is mandatory. 1, 2
Single Measurements Are Inadequate
A single low testosterone value is insufficient due to: 1, 7
- Diurnal variation in testosterone levels
- Assay variability between laboratories
- Transient suppression from acute illness or stress
Monitoring During Treatment
Once testosterone therapy is initiated, ongoing testing serves different purposes: 3
- Testosterone levels should be checked at 2-3 months after initiation or dose changes, then every 6-12 months once stable. 3
- Hematocrit monitoring is essential, as testosterone therapy can cause erythrocytosis; treatment must be withheld if hematocrit exceeds 54%. 2, 3
- PSA monitoring in men over 40 years is required to detect potential prostate abnormalities. 2, 3
The Bottom Line
Testosterone panels are performed to objectively confirm biochemical hypogonadism in symptomatic patients and to screen high-risk populations who may have testosterone deficiency even without classic symptoms. The testing must be done properly—with two morning measurements, appropriate follow-up testing to distinguish primary from secondary causes, and consideration of free testosterone in borderline cases—to avoid both underdiagnosis and inappropriate treatment. 1, 2, 7, 5