Why Has My Period Disappeared? When the Brain, Metabolism and Nutrition Hold the Answer

If your periods have become irregular or disappeared altogether, it is natural to wonder what has happened. Is it stress? Your diet? Exercise? Your weight? Your hormones? Or something going on with your ovaries?

The answer isn't always straightforward.

A menstrual cycle is the visible end point of a remarkably sophisticated conversation happening between your brain, metabolism, pituitary gland and ovaries. When that conversation changes, ovulation can change too — and when ovulation doesn't happen regularly, periods can become irregular or disappear.

There are many reasons this can happen, and it is important not to assume that every missing period has the same cause. Pregnancy, thyroid problems, raised prolactin, certain medications, perimenopause and other medical conditions can all affect the menstrual cycle.

But two of the situations I increasingly see in younger women are polyendocrine metabolic ovarian syndrome (PMOS), previously known as polycystic ovary syndrome (PCOS), and functional hypothalamic amenorrhoea (FHA).

Although both can result in periods becoming very irregular or disappearing, they represent very different physiological stories.

Understanding that difference matters, because the nutritional approach that may be helpful for one can be completely inappropriate for the other.

And there is one thing they have in common that I think we don't talk about enough:

The brain is right at the centre of the story.

Your ovaries aren't working alone

When we talk about women's hormones, it is easy to think about the ovaries as though they are running the show.

They aren't.

Your reproductive system is controlled by a communication network that begins in the brain.

One of the key areas involved is the hypothalamus, a small but incredibly important part of the brain that acts rather like a command and communication centre. It is constantly gathering information about what is happening elsewhere in the body — including energy availability, nutrition, stress and metabolic health — and using that information to help regulate many of the body's functions.

Reproduction is one of them.

The hypothalamus communicates with the pituitary gland through pulses of a hormone called GnRH (gonadotrophin-releasing hormone). In response, the pituitary releases two important reproductive hormones: LH (luteinising hormone) and FSH (follicle-stimulating hormone).

These hormones then communicate with the ovaries.

FSH helps ovarian follicles — the small structures containing immature eggs — develop. LH is involved in the maturation of the dominant follicle and the hormonal surge that triggers ovulation.

The ovaries then produce hormones including oestrogen and progesterone, and the cycle continues.

So your period isn't simply something your ovaries decide to produce once a month.

It is the result of a conversation that starts much further upstream.

And this becomes particularly interesting when we look at PMOS.

PMOS: when metabolism, hormones and the brain become intertwined

You may have heard of PCOS, but perhaps you haven't heard of PMOS.

PMOS stands for polyendocrine metabolic ovarian syndrome and is the newer name being introduced for the condition previously known as polycystic ovary syndrome.

I think the change in terminology is helpful because the old name could make the condition sound as though it was primarily a problem with the ovaries.

It isn't.

The "polycystic" part of the name has also caused confusion. The structures seen in the ovaries are generally follicles, not ovarian cysts, and not every woman with the condition has polycystic-looking ovaries.

More importantly, PMOS involves a much broader picture of metabolic, endocrine and reproductive health.

And this is where bringing the brain into the conversation is so important.

The brain is part of the PMOS story too

Remember that communication pathway we started with?

Brain → hypothalamus → GnRH → pituitary → LH and FSH → ovaries → ovulation

In PMOS, this signalling pathway can become altered.

The exact hormonal picture isn't identical in every woman. Some women have more obvious androgen excess, some have significant metabolic dysfunction, and some may have relatively subtle changes. PMOS is not one single hormonal profile that looks exactly the same from person to person.

But one of the characteristic features can be altered signalling between the hypothalamus, pituitary and ovaries.

The pattern of LH and FSH signalling can change, and this can affect how ovarian follicles develop and whether one reaches the stage where ovulation occurs.

At the same time, metabolic signals — particularly insulin — can influence the ovaries.

This is why I find it much more useful to think about PMOS as a whole-body metabolic and hormonal condition, rather than simply an ovarian problem.

So where does insulin fit in?

Insulin is often introduced to us as the hormone that controls blood sugar, but its role is much broader than that.

One of its main jobs is to help move glucose from the bloodstream into cells so that it can be used for energy.

In some women with PMOS, the body becomes less responsive to insulin. This is known as insulin resistance. The pancreas may compensate by producing more insulin to try to achieve the same effect.

And insulin doesn't only communicate with blood glucose.

It also interacts with the reproductive system.

Higher insulin levels can influence ovarian hormone production and contribute to increased production of androgens.

Androgens are sometimes described as "male hormones", but this is a rather unhelpful description. Women produce and need androgens too. Testosterone, for example, has important roles in muscle, bone, libido and general wellbeing.

The issue isn't having androgens.

It is having too much androgen activity or an altered balance of reproductive hormones.

When this happens alongside changes in insulin and brain–pituitary–ovarian signalling, the normal process of follicle development and ovulation can become disrupted.

A follicle may begin developing but not progress in the usual way. Ovulation may happen less frequently or not at all.

And this is the crucial link with periods.

No regular ovulation means no regular progesterone production.

Progesterone is produced after ovulation, so if ovulation isn't happening consistently, the normal rise and fall of progesterone doesn't happen either. The menstrual cycle can therefore become very irregular, with long gaps between periods or sometimes no period at all.

The problem isn't necessarily that the ovaries have "stopped working".

It may be that the signalling and hormonal environment isn't allowing ovulation to happen consistently.

But PMOS doesn't look the same in everyone

This is an important point because I think women can sometimes become confused when they read about PMOS online.

There isn't one universal PMOS woman.

Some women may have significant insulin resistance and be at a higher weight. Others may be lean and have relatively little obvious metabolic dysfunction.

Some may have prominent androgen-related symptoms such as acne, increased facial or body hair or scalp hair thinning. Others may have much subtler symptoms.

Some women have polycystic ovarian morphology on an ultrasound; others don't.

And hormone levels can vary considerably between individuals.

This is why a diagnosis shouldn't be based on one hormone result or one symptom in isolation.

It is the pattern that matters.

And this is where weight gets complicated

PMOS is often associated with higher body weight, but you do not need to be overweight to have PMOS.

Equally, being overweight does not mean that you have PMOS.

For women with PMOS who are at a higher weight and experiencing insulin resistance, conventional weight-loss advice can sometimes feel incredibly frustrating.

"Eat less."

"Exercise more."

"Cut your calories."

"Try harder."

These messages can completely miss the metabolic physiology that may be making weight regulation more difficult in the first place.

This is one reason I prefer to think about weight through a metabolic lens, rather than simply as a matter of willpower or calorie counting.

The aim isn't simply to make the number on the scales smaller. It is to improve the metabolic environment in which the body is operating.

That might involve improving insulin sensitivity, building and maintaining muscle, increasing physical activity in a way that is sustainable, eating sufficient protein and fibre, improving sleep, reducing reliance on highly processed foods and creating meals that support blood glucose regulation and appetite.

And importantly, these things can be worthwhile even if weight doesn't change.

Then there is a completely different reason for losing your period

Now imagine a different young woman.

She is conscientious, driven and hard-working. She exercises regularly and takes her health seriously. Perhaps she has gradually become more careful about what she eats, reduced portions or cut out certain foods because she wants to be "healthy".

Maybe she has started exercising more.

Perhaps she has begun to feel that she needs to earn her food — that she deserves to eat more on the days she exercises, but perhaps shouldn't eat as much on the days she doesn't.

She may not even realise that anything is wrong.

Her weight might be perfectly within the healthy range.

And then her periods become further and further apart.

Eventually, they disappear.

This could be functional hypothalamic amenorrhoea, or FHA.

And although the end result looks similar to PMOS — no ovulation and therefore no regular period — the physiology is almost the opposite.

Hypothalamic amenorrhoea: when the brain presses pause

The clue is in the name.

Hypothalamic.

We're back at that command centre in the brain.

The hypothalamus is constantly receiving information about the body's energy availability and physiological state.

It receives messages from hormones such as leptin and insulin, as well as information about glucose availability, stress and other aspects of the body's internal environment.

Leptin is produced primarily by fat cells and is one of the signals that helps the brain understand something about the body's available energy stores.

You can think of it as part of an ongoing conversation saying:

"We have enough energy stored and available."

When energy availability falls, leptin can fall too. Other metabolic signals change as well.

The brain may begin to receive a very different message:

"Resources are limited."

And if that message persists, the hypothalamus can reduce the pulsatile release of GnRH.

That matters because GnRH is what keeps the pituitary–ovarian communication system moving.

If GnRH signalling becomes disrupted, LH and FSH signalling changes.

The ovaries receive less stimulation.

Oestrogen production can fall.

Ovulation stops.

And the period disappears.

This is not the body failing.

It is the body responding to an environment in which it perceives that there may not be enough energy, or enough physiological safety, to support reproduction.

You don't have to be underweight

This is one of the most important things for young women to understand.

You do not have to be visibly underweight for hypothalamic amenorrhoea to occur.

A woman can have a completely "normal" BMI and still have low energy availability — particularly if she is exercising regularly, eating too little for her needs, restricting certain foods or experiencing significant psychological stress.

And sometimes there isn't one dramatic change.

It can be the accumulation of lots of small things.

Breakfast becomes smaller.

Lunch gets skipped because of work or study.

Exercise increases.

Carbohydrates are reduced.

An evening meal becomes lighter.

Stress increases.

Sleep deteriorates.

Individually, none of these things may seem particularly significant. Together, however, they can create an environment in which the body doesn't have enough energy available to support all of its physiological functions.

The body doesn't simply look at your weight and decide whether reproduction is possible.

It is responding to the whole picture.

Where does nutrition fit into the picture?

This is where nutrition becomes particularly interesting.

Hormones don't work independently of the rest of your physiology. Their production, conversion, receptor activity and cellular signalling all depend on a body that has sufficient energy and nutrients available.

Vitamins and minerals act as cofactors in hundreds of enzymatic reactions. Magnesium, zinc and the B vitamins are involved in processes ranging from energy production and neurotransmitter metabolism to hormone synthesis and cellular signalling.

But this is also where I think nutrition advice can sometimes become overly simplistic.

There isn't a magic nutrient that switches reproduction back on.

If the brain is receiving a consistent message that energy availability is too low, taking a handful of supplements while continuing to under-eat and over-exercise is unlikely to address the underlying problem.

I think of nutrition as part of the infrastructure.

The hormones are the musicians, but nutrition provides the instruments, the energy and much of the backstage support needed for the orchestra to function.

You need the whole system.

Two missing periods. Two very different nutritional approaches.

This is perhaps the most important distinction of all.

If a woman with PMOS and insulin resistance comes to me, I am not going to give her the same nutritional advice as a young woman with hypothalamic amenorrhoea.

With PMOS, we might be asking:

How can we improve metabolic health and insulin sensitivity?

How can we build meals that support blood glucose regulation? How can we increase protein and fibre? How can we support muscle mass and physical activity? How can we improve sleep and stress? How can we create an eating pattern that is sustainable rather than another restrictive diet?

For hypothalamic amenorrhoea, the questions may be very different.

Is she eating enough? Is she eating regularly enough? Is she fuelling her exercise appropriately? Has she unintentionally created an energy deficit? What is happening with stress and sleep? Is her relationship with food and exercise making it difficult for her to eat enough?

Sometimes the intervention may involve eating more rather than less.

Sometimes it may involve reducing exercise.

Sometimes weight gain may be necessary.

And sometimes we need to look more deeply at the beliefs around food, exercise and body image that have made adequate fuelling difficult.

Trying to treat hypothalamic amenorrhoea with a weight-loss mentality is clearly counterproductive.

But trying to treat PMOS by simply telling someone to "eat more" isn't the answer either.

The physiology matters.

And then there is bone health

There is another important difference between these two conditions.

With hypothalamic amenorrhoea, low oestrogen can become a significant concern for bone health.

Oestrogen plays an important role in maintaining bone, and this is particularly relevant during adolescence and early adulthood, when we are building much of our peak bone mass.

If periods disappear for a prolonged period because oestrogen levels are low, we need to take that seriously.

Not because we want to frighten anyone.

But because a missing period can sometimes be an early sign that the body isn't receiving the resources it needs.

This is one reason I don't believe that losing your period should simply be accepted as an inevitable consequence of being a serious athlete or someone who exercises a lot.

It is information worth paying attention to.

The bone-health picture in PMOS is different because oestrogen is not necessarily suppressed in the same way. That doesn't mean bone health is irrelevant in PMOS — nutrition, physical activity, metabolic health and other factors all matter — but prolonged low oestrogen is a particularly important consideration in hypothalamic amenorrhoea.

So why has your period disappeared?

This is the question I would really like more women — and the people supporting them — to ask.

Not simply:

"How do I get my period back?"

But:

"Why did my body stop ovulating in the first place?"

Because a missing period is a symptom.

It isn't a diagnosis.

PMOS is one possible explanation.

Hypothalamic amenorrhoea is another.

There are other causes too, which is why persistent or unexplained changes to your menstrual cycle deserve proper assessment rather than simply being treated with supplements or dietary changes.

Your period is a conversation, not an inconvenience

I think we sometimes talk about periods as though they are simply an annoying monthly event that we would ideally like to control.

But your menstrual cycle can tell you a great deal about what is happening inside your body.

Your brain is listening.

Your metabolism is listening.

Your pituitary gland is listening.

Your ovaries are listening.

And your period is, in many ways, the visible result of all those systems communicating with each other.

Sometimes the message is that the body has sufficient energy and the metabolic and hormonal conditions are right for ovulation.

Sometimes the message is that the metabolic environment isn't working optimally.

And sometimes the message is that the body doesn't currently have enough available energy, or enough physiological safety, to invest in reproduction.

Those messages require very different responses.

And that is why I don't believe in a one-size-fits-all approach to women's hormones.

I see young women from their teenage years onwards who have lost their periods, developed very irregular cycles or become worried about what their hormones are doing.

My first question isn't usually, "What supplement can we give you?"

It is:

"What is your body trying to tell us?"

Because once we understand the physiology behind the missing period, we have a much better chance of knowing what to do next.

And sometimes, the most useful thing we can do is simply stop trying to fight the symptom — and start listening to the signal.

Worried about your periods?

If your periods have become irregular, disappeared or changed significantly, it is worth understanding why rather than simply trying to make the symptoms go away.

I work with women and young women to look at the bigger picture — including nutrition, energy availability, metabolic health, digestion, stress, lifestyle and hormone patterns — and to help identify where further medical investigation may be appropriate.

If you're concerned about your menstrual cycle and would like some help working out what might be going on, you can get in touch with me here.