FSH, LH and oestradiol: what your hormone results mean, and why cycle timing matters

The Well Woman panel includes three reproductive hormones: FSH, LH and oestradiol. Together they show how your brain and ovaries are talking to each other. Unlike cholesterol or kidney markers, these hormones are meant to rise and fall. Understanding that rhythm is the key to reading your results.

What each hormone does

• FSH, follicle stimulating hormone, is made by the pituitary gland at the base of the brain. It tells the ovaries to grow a group of follicles, the small fluid sacs that each hold an egg.
• LH, luteinising hormone, also comes from the pituitary. A sharp surge of LH in the middle of the cycle triggers ovulation, the release of an egg.
• Oestradiol is the main form of oestrogen in women of reproductive age. It is made by the growing follicles and feeds back to the brain, telling it how the ovaries are responding.

This is a feedback loop. When the ovaries respond well, oestradiol rises and the brain eases off FSH. When the ovaries respond less, the brain pushes harder and FSH climbs. Much of what these results can tell you comes from reading the three together rather than one at a time.

How the levels move through a cycle

Day 1 of your cycle is the first day of full bleeding. In the first days, FSH is moderately raised to start the follicles growing, and oestradiol is low. Over the next week or so oestradiol climbs as one follicle takes the lead. Just before ovulation, oestradiol peaks and LH and FSH surge. After ovulation, LH and FSH drop back and oestradiol falls, then rises again more modestly in the second half of the cycle.

Because of this, labs print separate ranges for different phases of the cycle, and sometimes for after menopause. An oestradiol that would be high on day 3 may be exactly right on day 12. For this reason we do not quote single ranges for these hormones. The lab's range for your cycle phase is the one that applies.

If your cycle is irregular or absent

If your periods are unpredictable, it may not be possible to time the test. That is fine. Test when you can, and record the date of your last period. An irregular cycle is itself useful information, and a doctor may suggest repeating the hormones on a later date if the first results are hard to interpret.

Contraception changes everything

The combined pill, the patch, the ring, the injection and some other hormonal methods work by quieting the signals between the brain and ovaries. While you use them, FSH, LH and oestradiol reflect the contraception, not your natural cycle. The results are not wrong, but they cannot answer questions about your own hormone pattern or ovarian function. If that is the question, speak to a doctor before stopping any method.

Patterns a doctor looks for

These are examples of how the three hormones are read together. None of them is a diagnosis from one blood test.

• A high FSH with low oestradiol suggests the ovaries are responding less. This is expected around menopause. In a woman under 40 it needs repeating and a doctor's review, because early loss of ovarian function has its own implications for bone and heart health.
• Low FSH and LH with low oestradiol and missed periods suggest the signal from the brain has slowed. Common reasons include low body weight, intense exercise, stress and illness. A doctor may add other tests, such as prolactin, which is not part of this panel.
• An LH that is high relative to FSH is sometimes seen in polycystic ovary syndrome, but many women with PCOS have normal ratios. PCOS is diagnosed from periods, symptoms, testosterone and sometimes a scan, not from LH alone.
• A very high LH on its own may simply mean the sample caught the mid-cycle surge.

What these hormones cannot tell you

A single set of results cannot confirm whether you ovulated, predict when you will reach menopause, or tell you how fertile you are. They are a snapshot of one day in a system that changes daily. AMH, available as an add-on, and a doctor's history of your cycles add a great deal to the picture.

Your LifePrint report explains each result against the lab's range and flags anything that needs follow-up. If a hormone result is flagged, discuss it with a registered healthcare practitioner, who can put it together with your symptoms and history.