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Lost Your Period? Hypothalamic Amenorrhoea and Under-Fuelling

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Written by Felicity Bull, Accredited Practising Dietitian (APD)

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Losing your period can be unsettling, and it is easy to assume it is just stress or a busy few months. One common and often missed cause is functional hypothalamic amenorrhoea (FHA), where the brain turns down the hormones that drive your cycle because the body is under too much strain from not eating enough, exercising a lot, stress, or a mix of these. This guide explains what FHA is, why it matters for your bones and fertility, how it is diagnosed, and what recovery involves.

At a glance

  • Missing 3 or more periods in a row is a reason to see your GP.
  • FHA is a form of lost ovulation linked with stress, weight loss, a lot of exercise, or a combination, once other causes are ruled out.
  • In Europe and the US it is estimated to account for 20 to 35% of cases of secondary amenorrhoea (periods stopping after they have started).
  • The biggest long-term risk is bone loss. Stress fractures are a common problem in athletes without periods.
  • Recovery means meeting your body’s energy needs, usually with medical, dietitian and mental health support. Periods can return.

What is hypothalamic amenorrhoea?

The Endocrine Society’s clinical guideline describes FHA as a form of chronic anovulation (not releasing eggs) that is not due to an identifiable disease and is often associated with stress, weight loss, excessive exercise or a combination. The word functional means it is caused by things that can change, and the guideline notes that addressing those factors can restore ovulation.

In sport, the same pattern is part of Relative Energy Deficiency in Sport (REDs). The International Olympic Committee’s 2023 consensus describes low energy availability as a mismatch between what you eat and what you use in exercise that leaves the body’s total energy needs unmet, and lists impaired reproductive function and bone health as its best-documented effects.

Getting a diagnosis

The Better Health Channel advises seeing a doctor if you have missed 3 or more periods in a row, or had fewer than 9 periods in a year. FHA is a diagnosis made after other causes are ruled out. The guideline recommends a pregnancy test, a full physical examination and tests to exclude other causes. It also suggests a bone density scan after 6 or more months without periods.

Why it matters

  • Bones. The guideline calls bone loss, or not reaching peak bone mass, the most significant chronic risk, and notes stress fractures are a recurring problem among female athletes without periods.
  • Fertility. Without ovulation it is hard to conceive. Because the cause is functional, restoring energy balance can bring ovulation back.
  • Eating disorders. The guideline notes that loss of periods can accompany restrictive eating and in some cases indicates an eating disorder. The National Eating Disorders Collaboration lists loss or disturbance of menstruation as a warning sign.

What recovery involves

The Endocrine Society recommends correcting the energy imbalance to restore the hormone signals between the brain and ovaries, noting this often requires behaviour change. It recommends a multidisciplinary approach including medical, dietary and mental health support, and working with a dietitian on overall intake as well as nutrients like calcium and vitamin D. Recovery can mean eating more, adjusting training, managing stress and, for some people, weight restoration. That can feel hard, especially if food and exercise have become tied to how you cope, so support matters.

Periods do not always return straight away. The guideline notes amenorrhoea may persist for some time after the causes are addressed.

If food, exercise or your body feel out of control: you do not have to work this out alone. Talk to your GP, or call the Butterfly Foundation National Helpline on 1800 33 4673 (8am to midnight AEST, 7 days). Our eating disorder dietitian page explains how we can help.

Getting your cycle back

What recovery looks like depends on your history with food and exercise, your training, your stress, your bone health and whether you want to conceive. Felicity works alongside your GP and other health professionals to help you fuel your body enough, at a pace that feels manageable.

Felicity Bull is an Accredited Practising Dietitian. She sees clients in person in Mount Hutton (Newcastle and Lake Macquarie) and by telehealth across Australia. About fertility nutrition support.

Book with Felicity →

Common questions

What is hypothalamic amenorrhoea?

It is when periods stop because the brain reduces the hormones that drive ovulation, usually because of a mix of not eating enough for your needs, a lot of exercise, stress or weight loss, once other causes are ruled out.

Can you get your period back after hypothalamic amenorrhoea?

Yes. Because the cause is functional, addressing the energy imbalance can restore ovulation, although periods may take some time to return.

When should I see a doctor about missed periods?

See your GP if you have missed 3 or more periods in a row or had fewer than 9 periods in a year. A pregnancy test is the first step.

Is hypothalamic amenorrhoea the same as REDs?

They overlap. Loss of periods is one of the main signs of Relative Energy Deficiency in Sport, which happens when athletes do not eat enough for their training.

Does hypothalamic amenorrhoea affect bones?

Yes. Bone loss is the most significant long-term risk, and stress fractures are common in athletes without periods.

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Where this comes from

General information only, not personal advice. It does not replace advice from your doctor or dietitian.