If you’ve typed “why has my period stopped” into TikTok at 11pm, you’ve probably met the phrase hypothalamic amenorrhoea (HA) and then met forty conflicting explanations of it. Here’s the one I give my clients.
The short version
Your hypothalamus is a small region at the base of the brain that acts like an air-traffic controller for your hormones. Every few hours it releases a pulse of GnRH (gonadotropin-releasing hormone), which tells the pituitary to release LH and FSH, which tell the ovaries to grow a follicle, ovulate, and produce oestrogen and progesterone. That chain is your cycle.
When the hypothalamus senses that energy coming in isn’t covering the cost of everything you’re asking your body to do, it slows those pulses right down. The chain stalls. No ovulation, no bleed. That’s HA: functional hypothalamic amenorrhoea, meaning there’s nothing structurally wrong, the system has been switched off on purpose to protect you.
Why does the brain do that?
Reproduction is expensive. If the body thinks there isn’t enough fuel to run the essentials (heart, brain, temperature, immune system) and potentially grow a baby, it prioritises the essentials. It’s an ancient survival feature, not a fault.
The signal it’s reading is energy availability: the energy left over for your body to function once exercise has been paid for, relative to your fat-free mass. Research consistently shows menstrual function is disrupted when energy availability drops below roughly 30 kcal per kilogram of fat-free mass per day, and sometimes above that if the deficit is long-running or combined with other stressors.
Three things tend to push energy availability down:
- Under-fuelling, deliberately or not. Plenty of women I work with aren’t dieting. They’re busy, they skip breakfast, they eat “healthily” in a way that’s just too light for their training.
- High training load, especially endurance volume, HIIT every day, or a jump in intensity without a jump in food.
- Psychological stress and poor sleep, which raise cortisol and add to the load on the same system.
Usually it’s a combination. “I’m not even training that much” is something I hear often, and when we map out food against sessions, the gap is clear.
How do I know it’s HA and not something else?
HA is a diagnosis of exclusion. Your GP should rule out pregnancy, thyroid problems, high prolactin, polycystic ovary syndrome (PCOS) and premature ovarian insufficiency first, usually with blood tests and sometimes a scan. A classic HA picture is low or low-normal LH and FSH, low oestradiol, and often a low resting heart rate, feeling cold, poor sleep, low libido and slow recovery from training.
PCOS and HA get mixed up a lot because both can show cysts on a scan and both involve missing periods. The hormone pattern is different, and so is the treatment, so get the bloods done.
What about the pill?
The pill is often offered as a “fix”. It produces a withdrawal bleed, which can look reassuring, but it doesn’t restore your own oestrogen production or address the energy deficit that caused the problem. The bone, cardiovascular and psychological effects of low oestrogen carry on underneath. It’s a conversation to have with your GP, but it is not period recovery.
The first thing to do
Eat more, consistently, and look honestly at your training. That is the whole treatment in one sentence, and it is also much harder than it sounds, because the same drive that made you good at sport makes “do less and eat more” feel like failure. That’s why recovery works best with structure and support rather than willpower.
If you want to know where to start, book a free 15-minute call and we’ll talk it through.
Not sure where to start?
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This article is general information and not a substitute for individual medical advice. If you've been missing periods, see your GP to rule out other causes.
