What should be the next steps for a man with normal sperm count, low motility, low total testosterone (8.4 nmol/L) and normal follicle‑stimulating hormone (FSH) and luteinizing hormone (LH)?

Next Steps for Low Testosterone with Normal FSH/LH and Low Sperm Motility

Confirm the diagnosis by repeating a fasting morning total testosterone measurement, and if still low (8.4 nmol/L is below normal), measure sex hormone-binding globulin (SHBG) and calculate free or bioavailable testosterone to determine true androgen status before considering endocrinology referral. 1, 2

Immediate Diagnostic Confirmation Required

• Repeat morning fasting total testosterone is mandatory because testosterone levels show significant day-to-day variability and a single low value is insufficient for diagnosis 1, 2
• The current value of 8.4 nmol/L falls in the equivocal range (8-15 nmol/L) where calculated bioavailable testosterone (cBAT) or free testosterone should be reflexively measured 2
• Measure SHBG and calculate free or bioavailable testosterone using validated formulas, as total testosterone alone may be misleading—men with normal total testosterone but low free testosterone have genuine hypogonadal symptoms, while men with low total testosterone but normal free testosterone (typically obese men with low SHBG) often lack symptoms 3
• Free testosterone by equilibrium dialysis is the gold standard if available; avoid analog free testosterone immunoassays which are unreliable 2, 4

Interpretation of Normal FSH/LH with Low Testosterone

This hormonal pattern indicates secondary (hypogonadotropic) hypogonadism rather than primary testicular failure 5:

• In primary testicular failure, FSH and LH would be elevated (>7.6 IU/L for FSH) 6
• Normal or inappropriately low gonadotropins with low testosterone suggests hypothalamic-pituitary dysfunction 5
• Measure serum prolactin immediately to screen for hyperprolactinemia, a common reversible cause of secondary hypogonadism 5
• Consider pituitary MRI if confirmed testosterone remains very low (<150 ng/dL or ~5.2 nmol/L), even with normal prolactin, to exclude non-secreting pituitary adenomas 5
• Evaluate for other pituitary hormone deficiencies (TSH, free T4, morning cortisol, IGF-1) to distinguish isolated gonadotropin deficiency from panhypopituitarism 5

Addressing the Low Sperm Motility

• The combination of low testosterone with normal FSH suggests the hypogonadism may be contributing to asthenozoospermia (low motility) 6
• Do not start testosterone replacement therapy if fertility is desired, as exogenous testosterone suppresses FSH and LH through negative feedback, further impairing spermatogenesis 7
• If fertility is a goal and secondary hypogonadism is confirmed, gonadotropin therapy (hCG combined with FSH) is required rather than testosterone replacement, typically for 12-24 months 5
• Evaluate modifiable risk factors affecting sperm quality: smoking, excessive alcohol, obesity, medications (particularly opioids, glucocorticoids), environmental/occupational exposures, and heat exposure 6

When to Refer to Endocrinology

Refer to endocrinology if:

• Confirmed low testosterone persists on repeat testing with calculated low free/bioavailable testosterone 1, 2
• Prolactin is elevated, requiring further pituitary evaluation 5
• Secondary hypogonadism is confirmed and fertility is desired (requires gonadotropin therapy expertise) 5
• Pituitary imaging reveals abnormalities 5
• Multiple pituitary hormone deficiencies are suspected 5

Critical Pitfalls to Avoid

• Do not diagnose hypogonadism on a single testosterone measurement—variability is substantial and false positives are common 1, 2
• Do not rely solely on total testosterone in the borderline range (8-15 nmol/L)—free or bioavailable testosterone is essential for accurate diagnosis 2, 3
• Do not prescribe testosterone replacement if fertility is a concern—it will worsen sperm production by suppressing gonadotropins 7
• Do not miss reversible causes: prolactinoma, medications (opioids, glucocorticoids), obesity, sleep apnea, and systemic illness all suppress the hypothalamic-pituitary-gonadal axis 5
• Do not use analog free testosterone immunoassays—they lack reliability; use equilibrium dialysis or validated calculation methods 2, 4