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Why and how does menstruation cycles changes from the normal pattern?

When Is a Cycle or Menstruation Abnormal?


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We will discuss abnormal menstruations on this page. This page is just giving information and the information should never be used to diagnose or to treat menstrual abnormalities.

The discussion will be followed by a graphic illustration of the different conditions causing menstrual abnormalities. In a healthy normal woman menstruation occurs at regular intervals and it can cause anxiety if this changes. Possible disturbing changes are :
(i) It stays away
(ii)It is much less than normal and /or the interval between between bleedings increases.
(iii) It is much more than normal and /or the interval between bleedings decreases.
(iv) It becomes irregular , the interval between bleedings differs or changes and / or the duration of the actual bleeding differs or changes. It becomes impossible to predict when a period is going to start.

Scientifically the length of a cycle is calculated from the the starting day ( the day the bleeding begins) until the next starting day ( the day the next bleeding begins).The length of a cycle varies between 24 to 34 days with an average of 28 days. The duration of the actual bleeding is usually between 3- 7 days. ( these figures will slightly differ among different authors and is just an approximation). It is difficult to give a clear cut answer or to define abnormal menstruation accurately. If a person is worried about her bleeding , than it should be investigated.

The monthly changes that occur in the womb and ovaries are discussed elsewhere. Click here for the changes in the womb and here for the changes in the ovary. The changes in ovary lead to the release of the female hormones estrogen and progesterone at different stages of the cycle. The ovary is under the control of the pituitary gland , which in turn is under the control of the brain via the part of the brain called the hypothalamus. Click here . A disturbance at any level of this complicated control system can lead to menstrual abnormalities.

If the problem occurs in the control systems it is usually referred to as a hormonal imbalance. The problem can also occur due to other hormonal diseases.

There are other hormones in our body that have no direct influence on our sexual appearance or behavior. Examples are insulin, thyroid hormone and cortical steroid hormones. Abnormalities in the organs forming these hormones can also cause abnormal menstruations.

It is important to remember that menstrual abnormalities do not always originate in the uterus (womb).

In all instances of menstrual abnormalities medical checkups and examinations are advisable. It will usually include a complete physical examination and blood tests. It could also include more invasive examinations like a hysteroscopy or a DD & C. (Refer to gynecological operations ).

The blood tests will help the doctor to determine the level of the error if it is due to a control system problem . In other words it will help to determine if the problem is in the womb or the ovary or the pituitary gland. Samples of the endometrium obtained during surgery are send for examination. The condition of the endometrium indicates if there is a shortage of estrogen (a thin endometrium), excess of estrogen ( a very thick endometrium) or if there is progesterone present ( a vascular endometrium).

The examination of endometrial tissue is a very important and supply a lot of information in helping the doctor to make a proper diagnosis.

A graphic display of possible causes of menstrual abnormalities will now follow.


A Summary and Graphic Presentation of Abnormal Menstruation.

I The Absence of Menstruation (Medical term: Amenorrhoea)

We will use the term "amenorrhoea" on the rest of this page when referring to the absence of a menstrual period. There are to subgroups, primary and secondary amenorrhoea. The two most common causes of amenorrhoea, pregnancy and menopause, will be discussed elsewhere.

Secondary amenorrhoea is usually define as the absence of a cycle for more than 90 days in a previously normal individual. ( Three missed cycles). If periods are absent for more than three months it should always be investigated

Primary amenorrhoea occurs when menstruation is still absent at a age when a girl should be menstruating. The onset of the first menstruation varies in different populations but should be present in most populations at the age of sixteen. If a young girl's peers are all menstruating and she is not , she should be examined.

The conditions that cause primary amenorrhoea will be discussed later.

The following organs are involved in the occurrence of a normal menstrual cycle
(i) The endometrium.
(ii) The ovaries
(iii) The pituitary gland
(iv) The hypothalamus ( special area of the brain)

(i) The endometrium
(See also The Female Reproductive Organs and Normal Menstruation ).

The endometrium is usually either thick (stimulated by estrogen) or thin( estrogen stimulation absent).

The next drawing illustrate the thin endometrium seen in the absence of estrogen.

The next drawing illustrate the thick endometrium seen in continuous estrogen stimulation.

These drawings are included because the illustrate why hysteroscopies and /or DD&C's (womb scrapes) are done. During these procedures pieces (biopsies) of the endometrium are obtained and it helps in diagnosing the cause of the amenorrhoea.

(ii) The ovaries
(See also The Normal Ovary )

Menstruation depends on the secretion of hormones by the ovaries. In the absence of menstruation there is usually anovulation (the ovary is not releasing any egg cells).

There are a few possibilities

1. The follicles do not develop and no estrogen are produced. In this case the endometrium will be thin.

2. The follicles might developed but they do not rupture. Estrogen is produced but it is not opposed by progesterone and the endometrium becomes thick. In the latter case there is usually one or many estrogen producing follicles present.

Sonar examinations might show the presence of follicles and blood tests will determine the estrogen levels in the blood. Refer to this page and this one for more information.

(iii) The Pituitary Gland
(See also The Pituitary and the Menstrual Cycle )

The pituitary gland secrete many hormones that control the function of our bodies. Three of these hormones are important as far as menstrual function is concerned. They are FSH (Follicle Stimulating Hormone), LH (Luteinizing Hormone) and Prolactin. It is possible to determine the levels of these hormones via a blood test.

If the FSH and LH levels are high and the estrogen levels low, than the problem is usually in the ovary. The ovary is not responding to FSH and LH and the FSH and LH levels keep on increasing trying to get the ovaries to respond.

If the FSH is normal but the estrogen and LH are high , polycystic ovarian disease must be excluded. (See polycystic ovaries .

If the FSH , LH and Estrogen are all low , a problem in the pituitary or in the hypothalamus must be excluded.

A high prolactin level should also be investigated further.

The information obtained from blood tests combined with the microscopic diagnosis of the endometrium will give the medical practitioner a clear indication about the cause of the amenorrhoea.

Treatment will depend on the desirability of pregnancy. It a pregnancy is required ovulation induction treatment will be given else hormonal treatment will be given to normalize the cycle. It is very important in cases with a thick endometrium that the cycle should be normalized to prevent endometrial cancer later in life. ( please remember if your endometrium is thick , you do not have cancer, but it can develop into cancer over a period of years (more than ten years) if it is not treated.).

Highly effected medicines are now available to treat high prolactin levels. In many instances these drugs are able to shrink tumors (growths) of the pituitary gland. It is also important to remember that it is only a minority of persons with high prolactin levels that will develop pituitary tumors.

II Heavy Menstruation(Medical term: Menorrhagia).

There are three kinds of heavy menstruation. The volume of the bleeding is increase, the duration of the bleeding is increased or both the volume and duration are increased.

The causes of heavy menstruations are:

(i) Hormonal

(ii) Abnormalities in the genital tract

(iii)Other hormonal problems ( example diseases of the thyroid gland)

(iv) General diseases.

III Acyclic Bleeding. (Medical term Metorrhagia) This is bleeding that occurs at any time and the duration of the bleeding is unpredictable. Sometimes it lasts for weeks and than on other occasions only for a few days. without a cyclic pattern.


Hormonal Causes of Abnormal Menstruation

The hormonal causes are basically the same as the ones mentioned as causes for amenorrhoea. The heavy cycles can also be associated with either ovulation or the absence of ovulation. Biopsies or pieces of the endometrium are helpful in the diagnosis and for this reason DD&C and hysterocopy examinations are performed.

The next drawings will explain some of the different hormonal causes and their effects on the endometrium BUT NOT ALL OF THEM.

Inadequate endometrial stimulation (lack of hormones).

This drawing illustrates menorrhagia due to inadequate hormonal stimulation. The is a lack of estrogen and the endometrial lining growing slowly and it takes longer than normal before all the blood vessels are covered. The bleeding is therefore prolonged.

This type of menorrhagia is common towards the end of the reproductive years (the time before the onset of the menopause also known as the perimenopausal period).


The next two drawings illustrate prolonged bleeding in a case of a overstimulated endometrium.

The previous two drawings illustrate what frequently happens when excessive amounts of estrogen are secreted. Parts of the endometrium outgrow their blood supply and are discarded but not simultaneously. While the one part recovers another part is discarded and the bleeding continue for prolonged periods. In the illustrations the bleeding might decrease while the one area heals before the the other area starts bleeding.


Abnormalities of the Genital Tract

Abnormalities anywhere in the genital tract can cause abnormal bleedings. We will mention and discuss a few of them.


One of the most common causes of heavy bleeding is muscle growths or tumors of the womb. They are known by different names. Myomata, miomas, fibroids, fibro miomas leiomyomas etc.

They are tumors ( growths) that originate from the muscle layer of womb. The are usually benign ( non cancerous). Depending on their size, they can cause pain, heavy and or irregular bleeding, infertility, miscarriages, abdominal discomfort or when they are very large a tumor may felt palpated) in the lower part of the tummy.

The only treatment is surgical removal. The actual type of operation should be decided in consultation with the treating gynecologist. There are two main types of operations available:
(i) Removing the growths (myomectomy)
(ii) Removing the womb.(hysterectomy)

Fibroids usually cause excessive cyclic bleeding. The amount of blood loss is increased and /or the duration of the bleeding is increased. The mechanism is propably due to enlargement of the womb, thus incereasing the surface area of the endometrium.

The next drawings give an illustration of the different types of myomata.



This drawing shows a muscle growth developing deep in the center of the muscular layer.
 intra mural


This drawing shows a growth developing near the surface of uterus (womb). It it only attached to the womb via a pedicle.


This drawing shows a growth developing near the inner surface of the womb, bulging into the womb's cavity.
 sub mucosal


This drawing shows the common appearance of a uterus (womb) containing fibroids. The myomata are numerous, different sizes are present and the originate in different parts of the muscle layer.   multiple in different positions

If you want to see photographs of real wombs containing myomata click here




Polyps are small growths or thickening of the mucus membrane in the cervical canal or of the endometrium (the mucus membrane lining the wombs cavity). Some them might become cancerous if not treated but the majority will be benign. The usually cause acyclic bleeding ( bleeding that occurs any time , independent from the normal cycle).


The next drawings illustrate polyps.

The next drawing shows a uterus with three polyps. A cervical one protruding through the cervix (mouth of the womb) and two cervical polyps.




Fortunately cancers are not the most common cause of abnormal bleeding but they are the most serious and early detection is of the utmost importance.

The first drawing will illustrate early cervical ( mouth of the womb ) cancer. If regular papsmears (annually) are done, the changes are slim to develop cervical cancer. Most of the potential cancerous lesion will be detected before they become cancerous. See this page and this one

Early cervical cancer
Early Cx Cancer


The next drawing illustrates early endometrial cancer. This is a disease that usually effects older women (near and after the menopause). Any post menopausal bleeding bleeding should always be investigated to exclude endometrial cancer.



On the next page the disease known as endometriosis will be discussed. .


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LAST UPDATE: 19 January 2003

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