Map FSH, LH, testosterone, and prolactin onto the classic patterns of male infertility — and the next step each pattern implies.
Reference ranges are lab-specific. Enter testosterone as a number; classify FSH, LH, and prolactin as your laboratory reports them relative to its own reference interval. The total-testosterone low threshold of <300 ng/dL follows AUA/ASRM. Hormonal evaluation is indicated for impaired libido, ED, oligo/azoospermia, atrophic testes, or exam findings.
Pattern reference
Pattern
Testosterone
FSH / LH
Interpretation
Primary (hypergonadotropic)
Low
Elevated
Testicular failure / impaired production
Secondary (hypogonadotropic)
Low
Low or low-normal
Hypothalamic–pituitary; often treatable
Spermatogenic failure
Normal
FSH elevated, LH normal
Germinal compartment affected, Leydig preserved
Hyperprolactinemia
Low/normal
Low/normal
Prolactin high → suppresses GnRH; rule out prolactinoma/meds
Exogenous androgen
Normal/high
Suppressed
Iatrogenic; spermatogenesis suppressed, usually reversible
Evidence base
Schlegel PN, Sigman M, Collura B, et al. Diagnosis and treatment of infertility in men: AUA/ASRM guideline part I. Fertil Steril. 2021. — FSH + testosterone indicated for oligo/azoospermia, low libido, ED, atrophic testes; LH if T < 300 ng/dL; prolactin for hypogonadotropic picture or decreased libido.
Brannigan RE, Hermanson L, Kaczmarek J, et al. Updates to male infertility: AUA/ASRM guideline (2024). J Urol. 2024. doi:10.1097/JU.0000000000004180.
