InstalabFSH and LH
Should you take a FSH and LH test?
This test is most useful if any of these apply to you.
2 biomarkers included
- FSHFollicle-stimulating hormone drives egg follicle growth in the ovaries and supports sperm production in the testicles. When the gonads fail, FSH often climbs higher than LH, marking a primary problem in the ovaries or testicles.Why it mattersA high FSH usually means the ovaries or testicles are failing to respond, a sign of declining ovarian reserve or testicular function.
- LHLuteinizing hormone triggers ovulation in women and testosterone production in men. Paired with FSH, it reveals whether the pituitary's signal is balanced or skewed, as it becomes in polycystic ovary syndrome.Why it mattersAn LH running high relative to FSH points to disordered ovulation such as PCOS; low LH with low sex hormones points to a brain-level cause.
About FSH and LH
Your ovaries and testicles do not run themselves. They take orders from two hormones your pituitary gland releases, and reading those two signals side by side tells you whether the whole reproductive control system is working.
When trying to conceive stalls, periods go missing, or energy and libido fade, the relationship between these two hormones points to where the trouble sits: the brain's control center or the organs it directs. That is something neither hormone can show on its own.
What This Panel Reveals
This panel measures two pituitary messengers. Follicle-stimulating hormone (FSH) drives egg follicle growth in the ovaries and supports sperm production in the testicles. Luteinizing hormone (LH) triggers ovulation and, in men, testosterone production. Read together, they map the chain of command that runs from your brain down to your reproductive organs, a pathway clinicians call the hypothalamic-pituitary-gonadal axis (the brain-to-gonad control line).
The story is in the direction of the two numbers. Both hormones climb when the ovaries or testicles stop responding, because the brain shouts louder to compensate. Both stay low or unremarkable when the brain or pituitary is under-signaling. That single distinction separates a problem in the organ from a problem in the control system.
How to Read Your Results Together
| Pattern | What It Suggests |
|---|---|
| Both FSH and LH high, sex hormones low | The ovaries or testicles are failing to respond (a primary problem). In midlife women this fits the menopause transition; earlier it can signal primary ovarian insufficiency or testicular failure. |
| FSH and LH low or unremarkable, sex hormones low | The pituitary or hypothalamus is under-signaling (a central problem). This prompts a check for prolactin excess and other pituitary causes. |
| LH running higher than FSH with irregular cycles | A common signature of polycystic ovary syndrome (PCOS, a hormone imbalance that disrupts ovulation). |
| Both in range with regular cycles or normal symptoms | Reassuring. The control axis is balanced. |
In studies of adolescents with PCOS, LH ran at a median of 9.0 versus 3.7 international units per liter in those without it, and the LH-to-FSH ratio at 1.6 versus 0.7. In one adult cohort, an LH-to-FSH ratio above 0.749 identified PCOS with 86.3 percent sensitivity and 95 percent specificity; other studies have landed on different thresholds in different populations, so the ratio flags the pattern rather than serving as one fixed cutoff. Either way, it is the ratio, not either number alone, that carries the signal.
What to Do with Your Results
These two hormones set the direction; downstream hormones confirm it. Pair the results with estradiol in women or testosterone in men to complete the picture, and add prolactin when gonadotropins are low, since a prolactin-producing pituitary tumor is a treatable cause. If ovarian reserve is the question, anti-Mullerian hormone (AMH, a marker of remaining egg supply) tracks it more reliably than FSH, though an FSH above 10 international units per liter still suggests reserve is declining.
Because a single draw can mislead, retest an abnormal or ambiguous result rather than acting on one value. Track over time if you are watching a transition, such as approaching menopause or managing a diagnosed condition, and compare draws taken under the same conditions.
When Results Can Be Misleading
In menstruating women, both hormones swing across the cycle and spike at ovulation, so timing matters. Basal levels are most comparable when drawn in the early follicular phase; current guidelines point to cycle days 2 through 4, and one study found FSH readings hold steady across those early days. LH is also released in pulses and dips somewhat overnight, so a morning draw is often preferred, though the pulsing means any single value carries some inherent variability whenever it is drawn. Results can shift with the assay a lab uses, which is why comparing values across different labs can mislead. For menopausal symptoms, major guidance holds that measuring these hormones does not change care, since the diagnosis rests on your symptoms and cycle history.