Luteinizing Hormone to Follicle-Stimulating Hormone Ratio
Hormones marker
LH:FSH Ratio
Luteinizing Hormone to Follicle-Stimulating Hormone Ratio
Ratio of luteinizing hormone (LH) to follicle-stimulating hormone (FSH). In men, both gonadotropins are normally suppressed in parallel by exogenous androgens, so the ratio stays close to 1. A skewed ratio off-cycle or during PCT carries diagnostic information about HPTA recovery, primary versus secondary hypogonadism, and the relative balance of FSH versus LH stimulation.
PED Notes
Auto-calculated when both LH and FSH are present. On any AAS or TRT cycle, both LH and FSH are usually suppressed below the detectable limit; the ratio is meaningless in that state. The ratio becomes interpretable off-cycle, during PCT, or in a workup of secondary hypogonadism. A normal off-cycle male ratio is approximately 0.5 to 1.5 (FSH and LH in similar magnitude). A persistently high LH with low FSH suggests primary Sertoli cell dysfunction (FSH should rise to compensate but does not, sometimes seen in long-term AAS users with damaged spermatogenesis). A high FSH with normal LH is the classic pattern of testicular failure with preserved Leydig function. Useful in PCT to confirm both gonadotropins are returning, not just LH.
When high
This ratio is auto-computed. Adjust the underlying gonadotropins, not the ratio.
A high LH/FSH ratio (LH disproportionately higher than FSH) suggests:
- Sertoli cell dysfunction with preserved Leydig function: testicles produce testosterone in response to LH but spermatogenesis is impaired and FSH is not elevated to compensate
- Common after long-term AAS use that has damaged the spermatogenic epithelium
- May indicate the testes are responding to LH (testosterone is being made) but fertility is compromised independently
- Also seen in PCOS in women (not relevant for male athletes)
Workup:
- Semen analysis is the next step if fertility is a concern
- HCG monotherapy may help maintain Leydig function but will not fix Sertoli cell damage on its own
- Gonadotropin add-back with FSH-containing therapy (HMG, recombinant FSH) is the fertility-restoration pathway
- See HCG, HMG, and Sermorelin entries for protocol details
When low
This ratio is auto-computed. Adjust the underlying gonadotropins, not the ratio.
A low LH/FSH ratio (FSH disproportionately higher than LH) suggests:
- Primary testicular failure with preferential FSH elevation: damaged spermatogenic compartment, intact or partially intact Leydig response
- Klinefelter syndrome (47,XXY): often shows high FSH and high LH but FSH disproportionately higher
- Selective FSH-secreting pituitary adenoma (rare)
- Some recovery patterns post-AAS where FSH returns faster than LH
Workup:
- Total and free testosterone to assess Leydig function
- Karyotype if Klinefelter is suspected (small firm testes, gynaecomastia, tall stature)
- Pituitary MRI if FSH is markedly elevated without an obvious testicular explanation
- A SERM-based PCT (clomiphene or enclomiphene) preferentially stimulates LH and may help re-balance the ratio
This ratio is only interpretable when both LH and FSH are detectable. On suppressive AAS or TRT, both are usually below the assay limit and the ratio is not meaningful.
When the ratio adds value:
- Off-cycle HPTA assessment
- During PCT to confirm both gonadotropins are recovering, not just one
- Workup of secondary hypogonadism (low T with low or normal LH and FSH)
- Workup of fertility issues in former AAS users
Normal male reference (off-cycle):
- Roughly 0.5 to 1.5 in healthy men with functioning HPTA
- Both gonadotropins typically in the 1 to 8 IU/L range
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