13/10/2017 15:58 BST

Reasons Why Your Period Might Stop (If You're Not Pregnant)

Here's when you should be on red alert.

If there’s one thing a woman can count on in life, it’s her period. In fact, the average woman will have hundreds of periods between puberty and the menopause - that’s a hell of a lot of tampons.

When you expect your monthly bleed and it doesn’t turn up, it can be more than a little disconcerting. Aside from the obvious - being pregnant - there are many reasons why this might happen: it could be due to the hormonal contraception you’re taking, it could be because of a lifestyle change (for example if you’re stressed or exercising too much), or it could signal a health condition that shouldn’t go ignored. 

Here, experts discuss the various factors that may cause a pre-menopausal woman’s period to go into hiding and share advice on when to seek medical help.

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First of all, it’s important to remember that if your period is a no-show and you’re not taking hormonal contraception, it is still possible to get pregnant.

Many of the reasons behind your period’s absence are linked to hormones produced by three glands: the hypothalamus, the pituitary and the ovary. Michael Dooley, consultant gynaecologist at King Edward VII’s Hospital in London, likens the whole mechanism to a “finely-tuned clock”.

Breastfeeding, for example, is linked to the hypothalamus. When a woman begins breastfeeding her baby, she might notice her period stops - and this shouldn’t be a cause for concern.

“The hormones of breastfeeding upset the hypothalamus, the pituitary and the ovaries, which might stop a woman ovulating and therefore would stop her from menstruating,” Dooley tells HuffPost UK.

His reason for this is simple: the body doesn’t want that woman to get pregnant again as she needs to supply food to her newborn baby - so it alters the hormones to make menstruation to stop.

He adds that although breastfeeding isn’t a contraceptive, “full breastfeeding significantly reduces the chances of conception”.

What is the hypothalamus?

The hypothalamus is a gland in the centre of the brain which plays an important role in hormone production. 

It works alongside the pituitary gland to control the endocrine system, which is responsible for regulating things like metabolism, growth and development, tissue function, sexual function, reproduction and sleep.

What is the pituitary gland?

The pituitary gland is often called the ‘master gland’ because it controls several other hormone glands in your body, including the thyroid and adrenals, the ovaries and testicles, according to the Pituitary Foundation.

The hypothalamus controls the pituitary by sending messages to it.

What part does the ovary play?

The ovary secretes oestrogen and progesterone, which are very important for reproductive development and fertility.  

Having a severely low body weight and, surprisingly, stress can also disrupt a woman’s hormone function and stop her periods.

“With low body weight, whatever the cause of it - whether it’s through excessive amount of exercise, anorexia or bulimia, or malnutrition - the body doesn’t want you to get pregnant,” Dooley says.

According to Dr Alex Eskander, consultant gynaecologist at The Gynae Centre, women who exercise with great intensity experience disrupted hormone secretions, which in turn causes disruption in the ovaries and can result in their period not showing.

With severe weight loss, the body requires a certain amount of nutrients, like fat and protein, to function and maintain menstruation. So when the body receives inadequate amounts of these, the period doesn’t happen. 

Pamela Madsen, executive director of the American Infertility Association (AIA), previously told that a minimum of 22% body fat is necessary for normal ovulation and reproductive competence.

It’s worth adding here that, while women who are underweight or malnourished are less likely to become pregnant, it’s still possible they can.

Finally, hormonal contraception can make periods shorter, lighter and less painful. Progestogen-only methods such as the pill, implant, IUS and injection can make them stop them altogether.

Some women believe going without a period for months on end due to hormonal contraception can cause infertility - this is a myth, says Karin O’Sullivan from sexual health charity FPA. (For more information on how contraception affects the body, see our comprehensive list of pros and cons.)

Health Conditions

There are a few health conditions which disrupt hormone balance and can cause a woman’s period to stop, these include: thyroid disease, which results in the over- or under-function of the thyroid gland (responsible for producing thyroid hormones) and polycystic ovary syndrome (PCOS). With the latter, insulin resistance associated with the condition upsets the hormones, according to Dooley.

There are also some forms of medical treatment which can disrupt a woman’s period including some antidepressants, which affect hormones, and cancer treatments like radiotherapy and chemotherapy. The latter can destroy the eggs in the ovary and cause premature menopause, Dooley explains.

Underlying illnesses such as Cushing’s syndrome and Asherman’s syndrome, which affects the lining of the womb, might also disrupt menstruation. If this is the case, it’s important to speak to a GP.

Finally, it’s possible for tumours to grow in the ovary, adrenal gland or pituitary gland - all of which can mess up your monthly cycle and require urgent attention.

When to get help?

The take home message from experts is: if your periods stop, and it’s not because you’re taking hormonal contraception, you need to see a health professional.

Dr Alex Eskander advises women whose periods are late to take a pregnancy test first and foremost. Then, if the result comes back negative and your period still doesn’t show, you should see your GP. 

“It is not unusual to miss a period for between one and three months due to common factors such as stress,” says Dr Eksander. “Most of the time it will return to normal. But if your periods are late by three months, you should see your doctor or gynaecologist without delay.”

If you do see your doctor about this, it is possible they will carry out a physical examination, vaginal ultrasound and take measurements of your hormones. “Further detailed examination may be necessary if the amenorrhea (absence of your period) persists,” Dr Eksander adds.

Dr Helen Webberley, founder of the online healthcare service MyWebDoctor,  says it’s uncertain what the implications are for women who lose their hormones altogether or lose their cycles in between starting their period and the menopause. But she stresses it’s important to speak to a health professional about it.

“Current thinking is that to be without hormones is not good for us,” she tells HuffPost UK. “If your periods stop, you should find out why and replace your hormones if they are low.”