Can being underweight and having a history of irregular menstrual cycles cause abnormal uterine bleeding?

Underweight Status and Irregular Cycles as Causes of Abnormal Uterine Bleeding

Yes, being underweight and having a history of irregular menstrual cycles can cause abnormal uterine bleeding (AUB), primarily through hypothalamic dysfunction and anovulation. 1

Relationship Between Low Body Weight and Menstrual Dysfunction

• Low body weight can lead to hypothalamic amenorrhea (also called hypogonadotropic hypogonadism), which affects approximately 12% of women with temporal lobe epilepsy compared to only 1.5% of the general population 1
• Hypothalamic amenorrhea is associated with disturbed secretion of pituitary gonadotropins and low luteinizing hormone levels, causing amenorrhea or oligomenorrhea 1
• Rapid or significant fat mass reduction, even over as short as a 1-month period, can compromise menstrual function 1
• Low energy availability alters levels of metabolic hormones and substrates (insulin, cortisol, growth hormone, thyroid hormones, glucose, fatty acids, and ketones), which disrupts normal menstrual cycles 1

Irregular Cycles and Abnormal Uterine Bleeding

• Irregular cycles are often a sign of anovulation, which is a common cause of abnormal uterine bleeding 2, 3
• Anovulatory bleeding is typically characterized by irregular, unpredictable bleeding that can be heavy and prolonged 4
• Chronic anovulation can lead to prolonged unopposed estrogen stimulation of the endometrium, increasing the risk of endometrial hyperplasia and cancer 3
• Menstrual irregularity is defined as cycles <23 days (polymenorrhea), >35 days (oligomenorrhea), or no bleeding for >6 months (amenorrhea) 1

Diagnostic Considerations

• When evaluating abnormal uterine bleeding in underweight women with irregular cycles, consider:
  • Hormonal measurements including LH, FSH, prolactin, estradiol, and thyroid function tests 1
  • Assessment of energy availability and nutritional status 1
  • Evaluation for other causes of anovulation such as polycystic ovary syndrome, thyroid dysfunction, and hyperprolactinemia 3
  • Pelvic ultrasonography to rule out structural causes of abnormal bleeding 1, 2
  • Endometrial biopsy for women 35 years or older with recurrent anovulation or younger women with risk factors for endometrial cancer 3

Treatment Approaches

• For underweight women, addressing the underlying energy deficiency is crucial:

  • Increasing caloric intake to improve energy availability 1
  • Weight gain to achieve healthy body mass index 1
  • Reducing excessive exercise if present 1

• Medical management of abnormal bleeding:

  • Progestin-only contraception or combined hormonal contraception can regulate menstrual cycles 1, 2
  • Oral progesterone (400 mg daily at bedtime for 10 days) can be used to treat secondary amenorrhea 5
  • Nonsteroidal anti-inflammatory drugs can help reduce bleeding in ovulatory patterns 3
  • Tranexamic acid may be considered for heavy bleeding episodes 3, 6

• If medical treatment fails or is contraindicated, surgical options may include endometrial ablation or hysterectomy 1, 2

Important Caveats

• Abnormal uterine bleeding in adolescents with low body weight should prompt consideration of eating disorders 1
• Coagulation disorders, particularly von Willebrand disease, should be ruled out in cases of heavy menstrual bleeding, especially if present since menarche 7, 8
• Pregnancy complications must always be excluded in women of reproductive age with abnormal uterine bleeding 8
• Endometrial sampling is necessary in patients with risk factors for endometrial cancer 2
• Prolonged anovulation increases the risk of endometrial hyperplasia and cancer due to unopposed estrogen stimulation 3