28/04/2026
Louise was told her hormones were fine.
She had been waking at 3am for fourteen months and she’d had enough.
So she took herself off to her GP, they did some blood tests and when they came back her FSH was normal so her GP said it was probably stress. She suggested she cut back on caffeine and try to get to bed earlier.
Clearly her GP had good intentions but the problem was that FSH, the standard marker for perimenopause, was not the right test for Louise. FSH is a measure of follicle-stimulating hormone output and it rises when the ovaries are no longer responding as expected i.e. in perimenopause. However, this was not a test for how much progesterone Louise had and progesterone is what determines whether the brain's calming system is functioning at night.
Progesterone converts to something called allopregnanolone in the brain. Allopregnanolone amplifies GABA, the neurotransmitter promotes deep relaxation and initiates sleep. So when progesterone starts to fall early on in perimenopause, sleep becomes lighter and the brain does not settle.
A normal FSH does not tell you what progesterone is doing. It certainly does not tell you what progesterone is doing on day 21 of your cycle, which is where early luteal phase loss first shows up. That requires cycle-day-specific testing. Unfortunately most women never get this sort of testing because their FSH is normal and nothing flags the investigation.
Researchers studying perimenopausal hormonal transitions have consistently found that progesterone decline begins years before FSH rises reliably and progesterone loss can be a key driver.
If you have been told your hormones are fine and you still cannot sleep, then it may be that you just haven’t had the right hormones tested.
What would you do differently if you knew your standard blood test was not actually looking at the right thing? Let me know in the comments.
