Functional hypothalamic amenorrhea — often shortened to FHA — is one of the most common reasons for periods to stop in people who are otherwise well.
The name describes the mechanism. The hypothalamus, a small region of the brain, releases a hormone in pulses that sets the whole menstrual cycle in motion. When conditions look unfavourable, those pulses slow down or stop. The ovaries get no instruction, oestrogen stays low, and no period arrives.
“Functional” means nothing is damaged. The machinery works. It has been turned down.
What turns it down
Three things, usually in combination:
- Not enough energy. Eating less than the body is spending, whether deliberately or not.
- Too much physical demand. Training volume or intensity that outruns what is being eaten.
- Psychological stress. Sustained, significant stress, which the body reads as another reason to wait.
Very often all three arrive together, which is why it is common in people going through a demanding year while also trying to be disciplined about food and exercise.
It happens at every body size
This is the point most worth repeating. FHA is frequently assumed to be a condition of very thin people. It is not. It occurs at weights that look completely ordinary, and at weights that are above average.
What matters is the gap between intake and expenditure, not the number on a scale. People are regularly told they “look fine” and sent away, and that delay costs them time and bone density.
How it is diagnosed
It is what clinicians call a diagnosis of exclusion: other causes are ruled out first. Pregnancy, thyroid disease, raised prolactin, PCOS and premature ovarian insufficiency all have to be considered, which is why the blood tests come before the conclusion.
Typically FHA shows low or low-normal FSH and LH with low oestradiol, in the context of a history that fits. Your GP may refer you to a gynaecologist or endocrinologist.
What recovery generally involves
Where FHA is confirmed, the direction clinicians usually point people in is consistent: eat more, train less, address the stress, and give it time. Weight restoration is often part of it where weight has fallen.
Realistic expectations matter. Cycles commonly take several months to return, sometimes longer. Progress is not linear, and the absence of a period next month does not mean nothing is working.
Your clinician may also discuss bone density, and in some cases hormone treatment to protect bone while the underlying situation is addressed. That is a conversation to have with them rather than a decision to make from reading.
Where eating disorders fit
FHA and disordered eating overlap substantially, though not everyone with FHA has an eating disorder and not everyone with an eating disorder has FHA.
If food or exercise feels difficult to control, specialist support is the right route, and it works. Your GP can refer you, and Beat provides free, confidential support in the UK. Asking early makes it easier, not harder.
The thing worth holding onto
FHA is, in the great majority of cases, reversible. The body is waiting for conditions to improve. Most of the work is giving it the energy and the rest to believe they have.
General education, not a diagnosis. If your periods have stopped, your GP is the next step.
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