Learning Objective: Menstrual disorders and Hypothyroidism

A 35 year old Nurse came to the endocrine OPD with complaints of heavy menstrual bleeding during menstrual periods since last 4-6 months. She also had complaints of constipation on and off and generalized weakness.

She had menarche at age of 14 years. Her menses were always regular.  At present she was menstrual flow for 4 days, which are heaviest during the first 2 days. The length or her menstrual cycles is 24 days and has been the same as long as she can remember. She had similar problems about 1 year back for which she consulted a gynecologist who diagnosed her to have an ovarian cyst which ‘resolved’ with oral contraceptive pills.  The problem recurred again 4 months back.

The patient was diagnosed to have ? Subclinical hypothyroidism during her pregnancy for which she was prescribed levothyroxine. She stopped the medication on her own after delivery.

At present she is not on any medications. She works in the ICU and has shift duties. She says she has difficulty in sleeping when she is off duty. She claims she has gained a little weight since last year or so and she feels little depressed.

The patient’s mother has history of Hypothyroidism (Autoimmune). There is no family history of diabetes.

On examination she has

  1. Hirsutism (modified FG score of 10) and acne over the face
  2. Acanthosis nigricans
  3. No goiter
  4. No others signs or virilization.
  5. BMI is 23.5 kg/m2
  6. Waist circumference is 95 cm


She attributed her problems to the thyroid and got herself a thyroid function test which shows overt hypothyroidism. Anti TPO antibody is positive. She has Hb of 10 g/dl with microcytic hypochromic features and increased RDW

Here are the questions:

Q  Describes the attributes of a normal menstrual cycle

  • Frequency every 21 to 35 days
  • Occurs at fairly regular intervals
  • Volume of blood ≤80 mL ( < 1 tampon every 2 hours)
  • Duration is 5 days

Q  Define polymenorrhea and oligomenorrhea

  • Polymenorrhea- menstrual cycles <21 days
  • Oligomenorrhea – > 35 days

Q  What is the difference between amenorrhea and oligomenorrhea ?

Oligomenorrhea is increased length of menstrual cycle but the upper limit is not defined hence the differentiation between oligomenorrhea and amenorrhea is arbitrary. Amenorrhea is generally absence of menses for period > 3 months (some people use a cut off of 6 months) while oligomenorrhea is 35 days – 3 months or <9 cycles in a year.

Q  From a patient point of view, what is normal menstrual blood flow ?


  1. Need to Change tampon > 3 hours
  2. < 21 tampons required during the menstrual cycle
  3. No need to change tampon at night
  4. Patient is not anemic
  5. Clots are < 1 inch in diameter

Q  How much blood does 1 tampon soak ?

  • About 5 ml
  • A ‘super’ tampon may soak about 10 ml of blood
  • A pad may soak – 5-10 ml

Q  What is abnormal uterine bleeding ?

It refers to abnormalities of amount, duration or schedule of blood flow.

It could be either :

  1. Heavy menstrual bleed
  2. Prolonged menstrual bleed

The term menorrhagia should not be used any more

Q  What is heavy menstrual bleed ?

  1. More than 80 ml of blood flow during menstrual cycles
  2. Need to change tampon or pad every 2 hours
  3. Volume of bleeding interfering with daily activities

Q  What are some common causes of AUB is non pregnant women ?

It is given by PALM- COIEN classification

  • Polyp
  • Adenomyosis
  • Leiomyoma
  • Malignancy
  • Coagulopathy
  • Ovulatory dysfunction
  • Iatrogenic
  • Endometrial
  • Not otherwise classified

Q  What type of menstrual irregularities are seen with hypothyroidism ?


Women with hypothyroidism may have either oligomenorrhea or amenorrhea or Hypermenorrhea (menorrhagia)-AUB


Q  What is the frequency of menstrual irregularities in hypothyroidism ?

  • Evidence suggests that menstrual irregularity is less common than previously thought in patients with hypothyroidism.
  • In a study by Krassas et al
    • 77% had normal cycle
    • 16% has oligo-amenorrhea
    • 7% had hypermenorrhea
  • Oligomenorrhea and Hypermenorrhea were the most common patterns of menstrual irregularities.
  • Another study found no difference in incidence of hypermenorrhea in patients with hypothyroidism in comparison to controls. However, the same study found that patients with severe hypothyroidism were more likely to have menstrual irregularities than mild hypothyroidism. (Kakuno et al)

Q  Does the menstrual irregularity correlate with severity of hypothyroidism?

In the study quoted above, the menstrual irregularity was more common in women with overt hypothyroidism vs subclinical hypothyroidism and it did correlate with severity of hypothyroidism. However, the difference was not statistically significant.

Q  Does the presence of Anti-TPO antibody correlate with menstrual irregularities?

No.  Karassas et al did not found any difference in menstrual irregularities in patients with anti-TPO positive vs the entire group.

Q  Do the menstrual abnormalities improve with LT4 treatment?

It persists in almost half of the patients with treatment.


Q  What are the possible etiologies of AUB in hypothyroid patients?


  1. Estrogen breakthrough bleeding secondary to anovulation
  2. Decreased level of coagulation factors- VII, VIII, IX and XI seen in hypothyroid patients

Q  Is there any difference in menstrual irregularities reported from recent studies vs older studies ? If so why ?

  • Older studies showed a much higher prevalence of menstrual irregularities in hypothyroidism.
  • This was possibly due to delay in diagnosis of hypothyroidism leading to much severe symptoms


  1. Menstrual irregularities are often seen in hypothyroidism. However, prevalence of menstrual irregularities in hypothyroidism is reported less commonly in recent studies compared to older studies because of early diagnosis of hypothyroidism
  2. Oligomenorrhea is the most common menstrual irregularity reported in recent studies. Hypermenorrhea (AUB) is reported in about 7% of hypothyroid patients in comparison to 1% in controls.
  3. The menstrual irregularities may have an association with severity of hypothyroidism, but this needs more robust evidence.
  4. It has not relation with the presence of Anti-TPO antibodies.
  5. Menstrual irregularities may correct after treatment of hypothyroidism in about 50% of cases.



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