A single menstruation period may be defined as irregular if it is shorter than 21 days or longer than 36 days. A menstrual interval of 21 to 35 days is considered as normal (Pic. 1). 

If they are regularly shorter than 21 days or longer than 36 (or 35) days, the condition is termed polymenorrhea (menstrual interval shorter than 21 days) or oligomenorrhea (menstrual periods occurring at intervals of greater than 35 days), respectively. Special disorder called amenorrhoea is defined as an absence of menstrual cycles.


A menstrual interval shorter than 21 days was defined as polymenorrhea.

Patophysiology is unknown, but some scientists believe that it is because of accelerated follicular phase of menstrual cycle which leads to earlier onset of next menstruation. This could be caused by disruption in hypothalamic–pituitary–gonadal axis (plays a critical part in the development and regulation of a reproductive system). It is caused by higher activation of anterior pituitary gland, which produces luteinizing hormone (LH) and prolactine.

Polymenorrhoea occures more frequently in adolescent and perimenopausal women (the phase which takes place before the final cessation of periods). Sometimes shorten menstrual cycles follow after delivery of child when the pitutary gland is still more active. 


Oligomenorrhea is infrequent menstruation. More strictly, it is menstrual periods occurring at intervals of greater than 35 days, with only four to nine periods in a year. 

Oligomenorrhea can be a result of prolactinomas (tumors of the anterior pituitary). It may be caused by thyrotoxicosis (the condition that occurs due to excessive thyroid hormone), hormonal changes in perimenopause, Prader–Willi syndrome (a genetic disorder due to loss of function of specific genes), and Graves disease (an autoimmune disease that affects the thyroid).

Breastfeeding has been linked to irregularity of menstrual cycles due to hormones (prolactine) that delay ovulation.
Women with polycystic ovary syndrome (PCOS) are also likely to suffer from oligomenorrhea. PCOS is a condition in which excessive androgens (male sex hormones) are released by the ovaries. Women with PCOS show menstrual irregularities that range from oligomenorrhea and amenorrhea, to very heavy, irregular periods. The condition affects about 6% of premenopausal (before menopause) women.

Eating disorders can also result in oligomenorrhea. Although menstrual disorders are most strongly associated with Anorexia nervosa (an eating disorder characterized by a low weight), Bulimia nervosa (a serious eating disorder characterized by frequent episodes of binge eating followed by extreme efforts to avoid gaining weight) may also result in oligomenorrhea or amenorrhea. 


Amenorrhoea means the absence of a menstrual period in females. Amenorrhoea can be either primary or secondary.
Primary amenorrhoea refers to the failure of a period to start by the age of 16, in the presence of otherwise normal growth and development of secondary sexual characteristics (breast development, pubic hair) or, the failure of onset of puberty by the age of 13. 

Secondary amenorrhoea refers to the cessation of periods for six months or more after normal puberty and menstruation has occurred.

In order to evaluate amenorrhea, a medical history should be carefully taken so as to know if any genital anomalies, thyroid disorders, weight gain, or loss have been observed. Physical examination should be conducted to check for anatomical causes, as well as urine tests to exclude pregnancy. 

Treatment will depend on the underlying cause and may involve a combination of medical therapy (such as hormone therapy, nutritional advice or other medication) or surgery. Depending on the cause of the amenorrhea, referral to a fertility clinic may also be offered.


  • infrequent menstrual bleeding
  • more frequent menstrual bleeding
  • absence of menstrual bleeding
  • Associated diseases
  • eating disorders
  • prolactinomas
  • thyreotoxicosis
  • Prader- Willi syndrome
  • Graves disease
  • polycystic ovary syndrome (PCOS)


  • infertility

Risk factors

  • eating disorders
  • excessive exercise
  • high levels of prolonged physical or mental stress
  • brain tumour
  • brain surgery or injury
  • metabolic diseases 
  • genetic abnormality preventing normal ovarian function
  • premature ovarian failure, when the ovary goes into 'menopause' at an early age 
  • polycystic ovarian syndrome (PCOS)
  • pregnancy
  • abnormal uterus
  • lack of uterus
  • imperforate hymen causes an outflow obstruction
  • transverse vaginal septum can be anywhere along the tract between the hymenal ring and cervix
  • vaginal or cervical abnormality
  • antipsychotic medication


Every women should be checked at least once a year by her gynaecologist. In case of menstrual irregularities, the visit should be as soon as possible, to prevent complications.

Irregulat menstrual cycles are associated with high levels of prolactine (hyperprolactinaemia). Hyperprolactinaemia deregulates systems and processes affected by the pituitary and gonadal hormones.

The great response of prolactin in women of a reproductive age, who are not nursing or pregnant, leads to the inhibition of the normal pulsatile secretion of gonadotropin-releasing hormone (GnRH) of the hypothalamus. 

These, not so frequent, pulses of GnRH result in regular menses, on the one hand, but impaired follicular growth on the other. Greater impairment of pulsatile GnRH secretion leads to an anovulatory (ovulation does not occur) stage with menses being too frequent, too heavy, or infrequent. 

Further restraining of pulsatile GnRH secretion provokes deficient secretion of luteinizing hormone and follicle stimulating hormone (FSH), in amounts not adequate to induce a proper ovarian response. The ovulation does not occur and no egg will be relised.

That provokes a hypoestrogenized (low estrogen) amenorrheic and anovulatory cycle and side reactions of estrogen deficiency is comparable to what occurs during menopause or infertility.

Regular, periodical menstruation represents for women an aspect of normality and an indicator of female fertility. Menstruation plays an important role in women’s lives and any abnormalities interfere with their fertility and quality of life. 

Regular menstrual cycles are associated with anovulation. Very often hormonal therapy is sufficient for restoration of regularity of menstrual cycle and ovulation so women is able to concieve a child.

If the cause is due to anatomical anomalies which are operable, the corrective surgery is able to solve the problem.

Find more about related issues


Amenorrhoea ―sourced from Queensland Government licensed under CC BY 3.0 AU
Irregular menstruation ―sourced from Wikipedia licensed under CC BY-SA 3.0
Oligomenorrhea ―sourced from Wikipedia licensed under CC BY-SA 3.0
Eating disorder ―sourced from Wikipedia licensed under CC BY-SA 3.0
Polymenorrhea ―sourced from Fertilitypedia licensed under CC BY- SA 4.0
Menstrual cycle ―by NICH licensed under CC0
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