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Amenorrhea and Oligomenorrhea

From Mediwikis


Amenorrhoea is the absence of menstruation

This is further subdivided into:

  • Primary amenorrhoea
    • This is where no menstruation has been experienced by 16 years old
  • Secondary amenorrhoea
    • This is where menstruation has been experienced in the past but it has been absent for a period of 6 months or more


There are many different causes of amenorrhoea and one of the ways to try and remember them all is to think about the HPO axis (hypothalamic pituitary ovarian axis) and what could affect this. There is then a few extras that should be considered.

Remember that not all causes of amenorrhoea are pathological, non-pathological causes include pregnancy, post-menopause and lactation.

Hypothalamus (common)

Think psychological for most of these causes:

  • Anorexia Nervosa
  • Excessive exercise
  • Stress and anxiety

Other rarer causes include tumours and other SOL (space occupying lesions) (which can be ruled in or out with MRI). Also previous surgery and radiotherapy. Or Kallman's syndrome (primary GnRH deficiency - rare).

A reduction in the secretion of GnRH from the hypothalamus leads to low levels of LH and FSH causing amenorrhoea.


Could cause either primary or secondary amenorrhoea:

  • Pituitary hyperplasia or benign adenoma of the pituitary which can both lead to hyperprolactinaemia
    • Adenomas can be Micro (<10mm diameter) or Macro prolactinomas
  • Surgery
  • Other pituitary tumours (rare)

Secondary amenorrhoea can also be caused by Sheehan's syndrome post PPH (post partum haemorrhage in which there is a necrosis of the pituitary gland causing varying degrees of hypopituitism) (rare).

  • Note that prolactin is sometimes referred to as hPr.

Other than amenorrhoea there are other symptoms of hyperprolactinaemia, including:

  • Dry vagina
  • Reduced libido
  • Osteopenia (that sometimes progresses to osteoporosis)
  • Galactorrhoea (innapropriate milk secretion) (but not in all patients)


Could cause either primary or secondary amenorrhoea:

  • PCOS (polycystic ovarian syndrome) (common and important as has impact on fertility but usually causes oligomenorrhoea)
  • Premature ovarian failure (aka premature menopause)(rare)
  • Ovarian tumours (rare)
  • Resistant ovary syndrome

Causes specific to primary amenorrhoea:

  • Turner's syndrome
  • Other abnormalities of the X chromosomes leading to ovary malformations are extremely rare and cause conditions known as "gonadal dysgenesis"
Turner's Syndrome

Features include:

  • Short stature
  • Widely spaced nipples
  • Poor secondary sexual characteristics
  • Normal intelligence


These include:

  • Hypothyroidism and Hyperthyroidism
  • Adrenal tumours (rare)
  • Adrenal Hyperplasia (rare)
  • Medication (including some contraceptive methods)
  • Cushing's syndrome
  • Weight loss (can also occur in overweight patients who lose a lot of weight quickly)

Which could cause either primary or secondary amenorrhea.

Causes specific to primary amenorrhoea are congenital:

  • Obstruction of the menstrual outflow tract - imperforate hymen, transverse vaginal septum, absence of the vagina (rare)
  • Rokintansky's syndrome (absence of the vagina and functioning uterus) (rare)
  • Consitutional developmental delay (look for familial links)
  • Congenital Adrenal Hyperplasia (CAH) (rare)

Causes specific to secondary amenorrhoea are acquired:

  • Obstruction of the menstrual outflow tract - cervical stenosis, Ashermann's syndrome (uncommon - iatrogenic intrauterine adhesions post ERPC)
  • Pregnancy or Lactation
  • Menopause


REMEMBER: They could be pregnant so assess the likelihood of this by carefully obtaining information on sexual activity and any contraception that they may use.

Examination and Investigations


Management depends on the cause of the amenorrhoea and what the woman wants to achieve, for example if she wants children.


Oligomenorrhoea is where cycles are longer than 35 days and can be as long as 6 months. These are usually caused by an-ovulation or in women where ovulation is intermittent. Most oligomenorrhoea is "transient" and self limiting.


Remember that just post-menarche (up to 2 years) (until the HPO axis matures) and just pre-menopause the menstrual cycles may be irregular.

Causes include:

  • PCOS (common)
  • low/high BMI
  • Incipient POF (premature ovarian failure) where there is intermittent ovarian resistance (rare)
  • Mild endocrinopathies
    • Hypo/Hyper-thyroidism
    • Hyperprolactinaemia


A detailed history is important to try and ascertain the cause of the irregular cycles, getting the woman's ICE is key as with all presenting conditions that have an impact on fertility. You need to find out whether the woman wants to have children and provide reassurance.

Examination and Investigation

These are similar to those investigations used in amenorrhoeic patients and may include:

  • USS (ultrasound scanning) of the abdomen or transvaginally to look for PCOS
  • Hormone assays including TFTs


One of the first things that may help is to encourage the woman to gain/lose weight so that she resides within the "normal" BMI bracket. Treatment should be tailored to the cause.