Inhibin B
Fertility marker
Inhibin B
A hormone secreted by the Sertoli cells of the testes that reflects the integrity of the seminiferous tubules and the level of spermatogenesis. It provides negative feedback on pituitary FSH secretion and correlates with sperm production and testicular volume.
PED Notes
One of the most useful markers of testicular reserve in AAS users. Exogenous androgens shut down LH and FSH, which starves the testes of the signals that drive spermatogenesis; inhibin B falls as Sertoli-cell output declines. A low inhibin B in a suppressed athlete signals impaired spermatogenesis and, alongside FSH and sperm analysis, helps predict how readily fertility will recover during a PCT or a restart protocol. A very low or undetectable inhibin B after long or heavy cycles is a warning sign that recovery may be slow or incomplete.
When high
When high or high-normal:
- Generally reassuring, indicating healthy Sertoli-cell function and active spermatogenesis
- No intervention is needed; a robust inhibin B before starting a cycle is a good sign of testicular reserve
When low
When low (impaired spermatogenesis / suppressed testicular function):
Context in AAS users: Low inhibin B usually reflects HPG suppression from exogenous androgens, or long-term testicular atrophy. Interpret alongside FSH, LH, total testosterone, testicular volume, and a semen analysis.
Restart / fertility support (physician-supervised):
- hCG -- typically 500-1500 IU 2-3x/week; directly stimulates the testes (LH-mimetic) to restore intratesticular testosterone and support spermatogenesis
- hCG plus FSH (or hMG) -- adding recombinant FSH or hMG can further stimulate Sertoli-cell activity and raise inhibin B when hCG alone is insufficient
- SERMs (clomiphene 25-50mg or tamoxifen 10-20mg) -- raise endogenous LH and FSH to drive testicular recovery during PCT
- Time off cycle -- inhibin B and spermatogenesis recover slowly over months; premature judgement of infertility should be avoided
Supplements (adjuncts, modest evidence):
- Zinc -- 30mg/day (supports spermatogenesis and testicular function)
- CoQ10 -- 200-300mg/day and L-carnitine -- 2-3g/day (sperm quality)
- Consult a fertility specialist before pharmacological intervention, especially if conception is the goal
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Frequently Asked Questions
Reference Ranges
Standard Range