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Obstetrics GynecologyGynecologyAmenorrhea Oligomenorrhea

Amenorrhea & Oligomenorrhea

Introduction to Menstrual Disorders for MCCQE1

For the Medical Council of Canada Qualifying Examination Part I (MCCQE1), understanding menstrual disorders is a high-yield topic falling under the Obstetrics and Gynecology category. As a future Canadian physician, you are expected to demonstrate the Medical Expert role by differentiating between physiological absence of menses (e.g., pregnancy, menopause) and pathological causes requiring intervention.

This guide is structured to help you navigate the clinical presentation, etiology, and management of amenorrhea and oligomenorrhea, strictly adhering to SOGC (Society of Obstetricians and Gynaecologists of Canada) guidelines.

Definitions and Classification

Clear definitions are crucial for clinical reasoning and answering MCCQE1 vignette questions accurately.

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Key Definitions

  • Primary Amenorrhea:
    • Absence of menses by age 13 in the absence of secondary sexual characteristics.
    • Absence of menses by age 15 in the presence of secondary sexual characteristics.
  • Secondary Amenorrhea:
    • Absence of menses for 3 consecutive cycles or 6 months in a woman who previously had regular menses.
  • Oligomenorrhea:
    • Menstrual cycles occurring at intervals of >35 days.

Etiology: The Compartment System

To systematically approach the differential diagnosis, use the Anatomical Compartment System. This is a favored framework for Canadian medical education.

Uterus and Outflow Tract

  • Asherman’s Syndrome: Intrauterine adhesions (synechiae) often following D&C or endometritis.
  • Müllerian Agenesis (Mayer-Rokitansky-Küster-Hauser syndrome): 46,XX. Absent uterus/upper vagina, normal ovaries (secondary sex characteristics present).
  • Imperforate Hymen / Transverse Vaginal Septum: Obstruction causing cryptomenorrhea (cyclic pain without bleeding).
  • Androgen Insensitivity Syndrome (AIS): 46,XY. Defective androgen receptors. Phenotypically female, no uterus, scant pubic hair.

Clinical Evaluation

History Taking (The Canadian Context)

When taking a history for the MCCQE1, ensure you cover the CanMEDS roles, particularly Health Advocate, by screening for lifestyle factors and sensitive topics.

  • Menstrual History: Age of menarche, cycle length, duration.
  • Sexual History: Possibility of pregnancy (ALWAYS the first rule-out).
  • Review of Systems:
    • Galactorrhea/Headaches/Visual changes: Prolactinoma.
    • Hirsutism/Acne: PCOS.
    • Hot flashes/Vaginal dryness: POI.
    • Cyclic pelvic pain: Outflow obstruction.
  • Medical History: Chemotherapy, radiation, autoimmune disorders.
  • Medications: Antipsychotics, OCPs, herbs.
  • Lifestyle: Diet, exercise intensity, weight changes, stress.

Physical Examination

General Exam

  • BMI: <18.5 (Anorexia/FHA) or >30 (PCOS).
  • Thyroid: Goiter or nodules.
  • Stigmata of Turner’s: Short stature, webbed neck, wide-spaced nipples.
  • Signs of Androgen Excess: Hirsutism (Ferriman-Gallwey score), acne, balding.

Pelvic Exam

  • Tanner Staging: Breast and pubic hair development.
  • External Genitalia: Clitoromegaly (virilization), hymen patency.
  • Internal Exam: Presence of vagina/cervix/uterus, adnexal masses.

Diagnostic Approach: Step-by-Step Algorithm

Follow this logical progression for your MCCQE1 Clinical Decision Making (CDM) questions.

Step 1: Rule Out Pregnancy

Beta-hCG (urine or serum) is always the first test, regardless of sexual history provided in the vignette.

Step 2: Initial Hormonal Workup

If non-pregnant, order:

  • TSH: Rule out hypo/hyperthyroidism.
  • Prolactin: Rule out hyperprolactinemia.
  • FSH & LH: To localize the compartment (Ovary vs. Brain).

Step 3: Progestin Challenge Test (PCT)

Administer Medroxyprogesterone 10 mg PO x 10 days.

  • Withdrawal Bleed (+): Indicates presence of estrogen and patent outflow tract. Diagnosis: Anovulation (e.g., PCOS).
  • No Withdrawal Bleed (-): Indicates hypoestrogenism OR outflow obstruction. Proceed to Step 4.

Step 4: Estrogen + Progestin Challenge

Administer Estrogen x 21 days followed by Progestin.

  • Withdrawal Bleed (+): Outflow tract is patent. The problem is lack of estrogen (Ovary or Hypothalamus/Pituitary). Look at FSH from Step 2.
    • High FSH: Primary Ovarian Insufficiency (Ovarian failure).
    • Low/Normal FSH: Hypothalamic/Pituitary dysfunction (FHA).
  • No Withdrawal Bleed (-): Outflow tract obstruction (Asherman’s) or Müllerian agenesis.

Step 5: Advanced Imaging & Labs

  • Pelvic Ultrasound: To assess uterus and ovaries.
  • MRI Brain: If Prolactin is high or visual field defects present.
  • Karyotype: If Primary Amenorrhea + High FSH (Turner’s) or Primary Amenorrhea + Absent Uterus (XY AIS vs XX MRKH).

Specific Management & Canadian Guidelines

Polycystic Ovary Syndrome (PCOS)

According to the SOGC Guidelines, diagnosis requires 2 of 3 (Rotterdam Criteria):

  1. Oligo- or Anovulation.
  2. Clinical and/or Biochemical signs of Hyperandrogenism.
  3. Polycystic ovaries on Ultrasound.

Management:

  • Lifestyle: Weight loss is first-line.
  • Menstrual Regulation: Combined Oral Contraceptive Pills (COCPs) to prevent endometrial hyperplasia (cancer risk).
  • Fertility: Letrozole is first-line for ovulation induction in Canada (superior to Clomiphene for PCOS).

Functional Hypothalamic Amenorrhea (FHA)

Common in the “Female Athlete Triad” (Low energy availability, Amenorrhea, Osteoporosis). Management:

  • Multidisciplinary: Nutritionist, Psychologist, Physician.
  • Bone Health: Calcium/Vitamin D.
  • Note: COCPs do not restore bone density in FHA; weight gain and nutritional rehabilitation are required.

Primary Ovarian Insufficiency (POI)

Management:

  • Hormone Replacement Therapy (HRT): Essential until the natural age of menopause (~50-51) to protect bone and cardiovascular health.

Key Points to Remember for MCCQE1

High-Yield Summary

  • Most common cause of secondary amenorrhea: Pregnancy.
  • Most common cause of primary amenorrhea with normal secondary sexual characteristics: Müllerian Agenesis.
  • Turner Syndrome (45,X): High FSH, streak ovaries, primary amenorrhea.
  • Sheehan’s Syndrome: History of postpartum hemorrhage + failure to lactate + amenorrhea.
  • Prolactinoma: Treat with Dopamine Agonists (Cabergoline or Bromocriptine). Surgery is second-line.
  • Unopposed Estrogen: In PCOS, chronic anovulation leads to unopposed estrogen, increasing the risk of Endometrial Cancer.

Common Abbreviations

AIS   : Androgen Insensitivity Syndrome
COCP  : Combined Oral Contraceptive Pill
D&C   : Dilation and Curettage
FHA   : Functional Hypothalamic Amenorrhea
FSH   : Follicle-Stimulating Hormone
GnRH  : Gonadotropin-Releasing Hormone
hCG   : Human Chorionic Gonadotropin
MRKH  : Mayer-Rokitansky-Küster-Hauser (syndrome)
PCOS  : Polycystic Ovary Syndrome
POI   : Primary Ovarian Insufficiency
SOGC  : Society of Obstetricians and Gynaecologists of Canada
TSH   : Thyroid Stimulating Hormone

Sample Question

Clinical Scenario

A 17-year-old female presents to your family medicine clinic with a concern of primary amenorrhea. She has never had a menstrual period. She reports no cyclic abdominal pain. Her past medical history is unremarkable. On physical examination, her height is at the 60th percentile, and her BMI is 22 kg/m². Breast development is Tanner stage 4. Axillary and pubic hair are scant to absent. A blind-ending vaginal pouch is noted on the pelvic exam, and no cervix is palpable.

Question

Which one of the following is the most likely diagnosis?

  • A. Turner syndrome
  • B. Polycystic ovary syndrome
  • C. Müllerian agenesis (Mayer-Rokitansky-Küster-Hauser syndrome)
  • D. Androgen insensitivity syndrome
  • E. Prolactinoma

Explanation

The correct answer is:

  • D. Androgen insensitivity syndrome

Detailed Explanation: This patient presents with primary amenorrhea, normal breast development (indicating the presence of estrogen), but absent uterus (blind vaginal pouch, no cervix). The differential diagnosis for primary amenorrhea with breast development but absent uterus is primarily between Müllerian Agenesis (MRKH) and Androgen Insensitivity Syndrome (AIS).

  • Androgen Insensitivity Syndrome (AIS): These individuals have a 46,XY karyotype. The testes produce testosterone (converted to estrogen peripherally, causing breast development) and Anti-Müllerian Hormone (AMH), which causes regression of the Müllerian structures (uterus, fallopian tubes). However, due to defective androgen receptors, they do not develop male external genitalia or sexual hair (pubic/axillary hair is androgen-dependent). The key finding here is the scant/absent pubic hair.
  • Müllerian Agenesis (Option C): These patients are 46,XX. They have normal ovaries producing estrogen and androgens. Therefore, they have normal breast development AND normal pubic hair.
  • Turner Syndrome (Option A): Typically presents with short stature, webbed neck, and lack of breast development (due to streak ovaries/low estrogen) unless mosaicism is present.
  • PCOS (Option B): Typically presents with secondary amenorrhea/oligomenorrhea and signs of hyperandrogenism (hirsutism), not absent uterus or primary amenorrhea with absent pubic hair.
  • Prolactinoma (Option E): Would cause amenorrhea via HPO axis suppression but does not affect anatomical development of the uterus or vagina.

References

  1. Society of Obstetricians and Gynaecologists of Canada (SOGC). (2018). Ovulation Induction in PCOS. Clinical Practice Guideline No. 362. https://sogc.org 
  2. Society of Obstetricians and Gynaecologists of Canada (SOGC). (2019). Canadian Consensus on Female Nutrition: Adolescence, Reproduction, Menopause, and Beyond.
  3. Medical Council of Canada. (2023). MCCQE Part I Objectives: Menstrual Cycle Irregularities.
  4. Gordon, C. M., et al. (2017). Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism.
  5. Toronto Notes. (2023). Gynecology: Amenorrhea. Toronto: Toronto Notes for Medical Students, Inc.
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