Testosterone Testing in a 17-Year-Old Adolescent
Testosterone testing in a healthy 17-year-old is generally not appropriate unless there are specific clinical indicators of delayed puberty, hypogonadism, or other endocrine disorders.
When Testing IS Appropriate
Testosterone measurement should be considered in adolescents only when specific clinical concerns are present:
Clear Indications for Testing
Delayed or absent pubertal development – If the adolescent has not entered puberty by age 14 (no testicular enlargement, no pubic hair development), or if pubertal progression has stalled, morning testosterone measurement is warranted to assess hypothalamic-pituitary-gonadal axis function 1, 2.
Constitutional delay assessment – In boys with short stature and delayed puberty, early morning plasma testosterone (measured at 8:00 AM) can predict imminent pubertal development; a morning testosterone ≥0.7 nmol/L (approximately 20 ng/dL) indicates that 77% will enter puberty within 12 months 2.
Suspected hypogonadism with clinical features – Testing is appropriate when there are physical examination findings such as testicular volume <2 mL beyond age 14, absence of secondary sexual characteristics, or signs of androgen deficiency 1, 2.
Specific medical conditions – Adolescents with conditions known to affect testosterone production (e.g., Klinefelter syndrome, pituitary disorders, prior chemotherapy or testicular radiation, chronic illness) should undergo testing 3, 1.
When Testing is NOT Appropriate
Nonspecific symptoms alone – Complaints of fatigue, low energy, poor concentration, or mood changes in an otherwise healthy adolescent do not justify testosterone testing, as these symptoms show minimal correlation with testosterone levels and do not reliably improve with treatment even in confirmed hypogonadism 4, 1.
Athletic performance or body composition concerns – Testosterone testing for muscle building, weight loss, or athletic enhancement has no evidence-based indication and should not be performed 4.
Routine screening in asymptomatic adolescents – There is no role for screening testosterone levels in healthy adolescents without clinical signs of pubertal delay or endocrine dysfunction 1, 5.
Diagnostic Approach When Testing is Indicated
If clinical features warrant evaluation:
Timing is critical – Obtain morning (8:00-10:00 AM) total testosterone measurement, as diurnal variation causes lower values later in the day 4, 6.
Repeat confirmation – A single low value requires confirmation with a second morning measurement before diagnosing hypogonadism 4, 7.
Age-specific reference ranges – Young men aged 20-24 have a middle tertile testosterone range of 409-558 ng/dL, with a lower cutoff of 409 ng/dL for this age group—substantially higher than the 300 ng/dL threshold used in older men 7. For a 17-year-old, interpretation must account for pubertal stage rather than adult reference ranges 2.
Additional hormonal assessment – If testosterone is low, measure LH and FSH to distinguish primary (testicular) from secondary (hypothalamic-pituitary) hypogonadism, as this distinction is critical for treatment planning and fertility preservation 4, 1.
Common Pitfalls to Avoid
Do not test based on vague symptoms – Fatigue, low energy, and mood complaints are nonspecific and do not correlate with testosterone levels in adolescents 4, 1.
Do not use adult diagnostic thresholds – The 300 ng/dL cutoff was derived from older men and does not apply to adolescents or young adults 7.
Do not test outside morning hours – Afternoon or evening measurements risk false-positive diagnoses due to normal diurnal decline 4, 6.
Do not diagnose on a single measurement – Testosterone levels vary significantly; confirmation with repeat testing is mandatory 4, 7.
Special Considerations
Obesity and metabolic factors – Obese adolescents may have lower total testosterone due to increased SHBG binding and aromatization to estradiol, but this does not necessarily indicate true hypogonadism requiring treatment 4, 1.
Anabolic steroid or illicit drug use – These are increasingly recognized causes of secondary hypogonadism in young men and should be screened for in the history 1.
Fertility preservation – If hypogonadism is confirmed in an adolescent, treatment planning must consider future fertility; exogenous testosterone causes azoospermia, whereas gonadotropin therapy preserves spermatogenesis 4, 1.