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Articles/Why Is My Period Late? Common Causes And Reasons

Why Is My Period Late? Common Causes And Reasons

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Dr Len Kliman Associate Professor
15 mins read September 14th 2022
a woman holding up a calendar with red ticks on it marking down her period cycle

A woman’s menstrual cycle typically lasts around 28 days, but it can vary naturally. Periods can range from late (up to 35-40 days) to absent altogether. The question is, when do late or missed periods become a cause for concern?

While a one-time delay is usually nothing to worry about, persistent changes can indicate an underlying issue. If your cycles are consistently longer than usual (by a week or more) or you experience complete absence of periods (secondary amenorrhea), it’s important to see a doctor to explore the cause.

Remember, for women of reproductive age, a late period always warrants a pregnancy test first.

a woman holding up a calendar with red ticks on it marking down her period cycle

Reasons For Late Periods

The most common reasons for late periods include:

  • Stress
  • Obesity
  • Increased Exercise
  • Perimenopause
  • Eating Disorders
  • Polycystic Ovarian Syndrome
  • Birth Control
  • Chronic Diseases
  • Thyroid Issues

1. Stress

Periods are ultimately controlled by a part of your brain called the hypothalamus. This area of your brain is also influenced by other parts of your brain therefore conditions such as stress, anxiety, depression and significant changes in lifestyle can influence your periods. It is also important to remember that drugs that are used to treat depression can influence your periods as a side effect of the drug. Similarly, certain drugs that are used to treat nausea can also influence your menstrual cycle.

Prolactin which is a hormone produced by the pituitary gland is a stress hormone. In other words, the level of prolactin increases in response to stress. This means that there is actually a distinct hormonal mechanism whereby stress can influence your periods. Similarly, abnormalities of the pituitary gland such as a small benign tumour called an adenoma which releases large amounts of prolactin can also interfere with your menstrual cycle. There are specific treatments for this condition.

2. Obesity

Being overweight can affect the part of the brain that controls the menstrual cycle. This is especially the case when weight gain occurs over a relatively short period of time and there is an increase in the BMI (body mass index).

3. Increased Exercise

It is often noted that ballerinas and marathon runners have irregular cycles or cease having periods altogether. It has been shown that you have to have a certain percentage of body fat to cycle appropriately. Losing too much body fat can stop your body from ovulating properly, and stop your cycle altogether.

4. Perimenopause

Perimenopause is the period of time when oestrogen production is slowly reducing due to changes that are occurring in the hypothalamus, as well as changes that are occurring in the part of the brain that controls your menstrual cycle and your hormone production.

Find out more about the signs and symptoms associated with Perimenopause. 

5. Eating Disorders

A significant reduction or increase in body weight can influence the hypothalamus which controls your menstrual cycle. Therefore, it can have a distinct effect on your menstrual cycle either by preventing ovulation, seeing an increase in delayed periods or turning off your menstrual cycle altogether. When weight loss is associated with a low oestrogen level, the eating disorder can be associated with significant health issues such as osteoporosis or thinning of the bones.

6. Polycystic Ovarian Syndrome

Polycystic ovarian syndrome is not an abnormality primarily of the ovaries, it’s an abnormality of the controlling centre in the hypothalamus as well. This results in the disordered release of hormones from your pituitary gland that controls ovarian and hormone production and the development and release of your eggs.

If ovulation does not occur because of polycystic ovary syndrome then there are effective treatments if you wish to become pregnant.

7. Birth Control

Oral contraceptives work by feeding back to your brain a message that you have sufficient hormones within your body and this turns off the release of controlling hormones that primarily act to result in ovulation. Therefore ovulation does not occur whilst you are on the pill.

For some women on the pill the lining of the uterus becomes particularly thin and when the time for their period comes, there is very little or no tissue to come away and in this case, they will notice absent or infrequent periods. Some women, especially women who have painful periods or premenstrual dysphoria disorder choose to avoid having periods altogether by taking the active hormones in the pill continuously. This is usually an effective form of treatment.

8. Chronic Diseases

Any significant chronic illness can interfere with your menstrual cycle because of the interaction with the controlling centre within your brain. This can also be exacerbated if your chronic illness is associated with weight changes. Conditions such as inflammatory bowel disease, autoimmune disorders or chronic thyroid conditions can all interfere with your menstrual cycle and the frequency of your periods.

9. Thyroid Issues

It is well known that an underactive thyroid gland can be associated with shutting off ovulation and result in a change in your menstrual cycle. Similarly, an overactive thyroid gland can also affect your menstrual cycle and either make your periods infrequent or disappear altogether.

a doctor sitting with a woman during a consultancy

Why Is It Important To Treat Late Periods?

There are two reasons why it may be important to treat a woman with overdue or absent periods. The first reason is that if you are not ovulating and wish to become pregnant – this may involve the use of simple fertility medication to restart your periods but more importantly restart ovulation so you have the ability to conceive.

The second reason for restarting your periods is if you have absent periods often due to being underweight or over-exercising. This can result in a low circulating oestrogen level which in itself is not good for your general health and wellbeing. Oestrogen hormone is important for bone strength (you can develop osteoporosis or thin of the bones) but it is also cardioprotective (protects you from heart disease) and also keeps your skin, especially your vaginal skin moist and in good condition.

a doctor and woman sitting together during a consultation

When to See Your Gynaecologist

If you notice a significant disturbance in the length of your cycle or the absence of periods altogether for more than 3 months, it’s worthwhile making an appointment with your gynaecologist. From there, the appropriate investigations will take place and underlying causes can be excluded.

Associate Professor Len Kliman has been treating women with these disorders for over 30 years and has a sensible regime to address the problem and come up with a solution and treatment plan. Book an appointment with Dr Len Kliman and find out more about your period cycle, and what could be causing it to come late.

FAQs about Late Periods
  • What Is The Process of a Period?
    A woman’s periods are controlled by a network that starts at the part of the brain called the hypothalamus, where a hormone called GnRH begins to pulse from that area of the brain. These pulses which are at a specific frequency and strength or amplitude, send the message to the pituitary gland to release two hormones that act on the ovaries. These hormones are FSH (follicle stimulating hormone) or the hormone that makes eggs develop and a second hormone called LH (luteinising hormone) which acts to release the eggs. In association with the release of these hormones, your ovaries produce three different types of oestrogen hormone as well as progesterone hormone after ovulation and a small amount of male hormone (testosterone) which is responsible for libido in women.
  • When Does Your Menstrual Cycle Usually Start?
    A normal menstrual cycle or period that commences at what is called menarche usually occurs around the age of 12-13 in Australia. This varies enormously from person to person.
  • What Is Considered A Normal Menstrual Cycle?
    A typical menstrual cycle will be 28-30 days and the periods on average last around 5 days.
  • How Late Can My Period Be Without Being Pregnant?
    The majority of women with late or absent periods are not pregnant and often have a specific cause or condition that cause infrequent periods (known as idiopathic hypothalamic oligomenorrhoea) or absent periods for more than 3 months (secondary amenorrhoea). It is always wise to have a pregnancy test and exclude pregnancy once your period is more than one week overdue.
  • Why Do I Have Brown Spotting But No Period?
    There are a number of reasons why your periods can be lighter and appear different in colour and consistency. It usually implies that the lining of the uterus is thinner than normal and therefore sheds differently. Small amounts of blood may be retained within the uterus and turn brown or old prior to passing from your body. However, abnormal brown spotting needs to be fully investigated to exclude the unlikely possibility of a precancerous or a cancerous condition.