FSH (Follicle-stimulating hormone)
Pituitary-side signal that drives spermatogenesis. The single most useful marker for testicular function.
What it is
FSH is released from the anterior pituitary and acts on Sertoli cells in the testes. It is the primary hormonal driver of spermatogenesis. Levels respond to feedback from inhibin B (a Sertoli-cell hormone) and testosterone.
Why it matters
FSH separates causes of male infertility better than any single other marker. A man with low sperm count and high FSH almost certainly has a testicular (primary) problem. A man with low sperm count and low or normal FSH is far more likely to have a pituitary or hypothalamic (secondary) cause that can sometimes be reversed.
Adult male reference range
Adult male reference range is roughly 1.5–12.4 IU/L. Values above 7.6 IU/L predict reduced sperm production with high specificity in many cohorts.
Role on the panel
On the Hormone Panel 01, FSH is read with LH and total T to localise the cause of any abnormal result. It is the single biggest reason a hormone panel beats a standalone testosterone test for fertility questions.
When it reads low
Low FSH with low testosterone points toward secondary hypogonadism — pituitary insufficiency, severe energy deficit, opioid use, or recent androgen/SARM use suppressing the axis.
When it reads high
Elevated FSH with low testosterone or known low sperm count is the textbook signature of primary testicular failure (e.g. post-orchitis, post-chemotherapy, varicocele, Klinefelter syndrome).
Common questions about this marker.
Order the Hormone Panel 01.
All six markers, one finger-prick, ISO-certified German lab. Physician review and a plain-language report in 3–5 working days.