When do uterine fibroids cause iron deficiency anemia?

Uterine Fibroids and Iron Deficiency Anemia

Uterine fibroids cause iron deficiency anemia primarily through menorrhagia (heavy menstrual bleeding), which is the most frequent symptom of fibroids and often results in significant blood loss exceeding 80 mL/month. 1

Mechanism of Anemia in Fibroid Patients

• Menorrhagia (heavy menstrual bleeding) is the most common symptom of uterine fibroids that leads to iron deficiency anemia 1
• Fibroids, particularly submucosal fibroids that distort the uterine cavity, can cause abnormal uterine bleeding patterns and increased menstrual blood loss 2
• Heavy menstrual blood loss (≥80 mL/month) is a significant risk factor for iron deficiency anemia, affecting approximately 10% of women in the United States 1
• Chronic blood loss from fibroid-related bleeding depletes iron stores faster than they can be replenished through dietary intake alone 2

Risk Factors for Developing Iron Deficiency Anemia with Fibroids

• Location of fibroids: Submucosal fibroids (those that protrude into the uterine cavity) are most likely to cause heavy bleeding and subsequent anemia 2
• Size and number of fibroids: Multiple or large fibroids increase the risk of heavy menstrual bleeding 3
• Race: Black women have a higher prevalence of fibroids (>80% by age 50) and are more likely to develop clinically significant disease at an earlier age 1
• Inadequate dietary iron intake: Only one-fourth of women of childbearing age meet the recommended dietary allowance for iron through diet 1
• Previous diagnosis of iron deficiency anemia increases risk for recurrent anemia 1

Clinical Presentation and Severity

• Iron deficiency anemia due to fibroids can range from mild to life-threatening:
  • Mild cases may present with fatigue, weakness, and decreased exercise tolerance 2
  • Severe cases can present with hemoglobin levels as low as 1.1-3.0 g/dL, requiring urgent intervention 4, 3
• Patients may delay seeking treatment despite prolonged heavy bleeding, leading to severe, potentially life-threatening anemia 3
• Some patients remain ambulatory and hemodynamically stable despite critically low hemoglobin levels, masking the severity of their condition 4

Diagnostic Approach

• Evaluate for iron deficiency anemia in any woman with uterine fibroids who reports heavy or prolonged menstrual bleeding 1
• Laboratory assessment should include complete blood count with hemoglobin, hematocrit, and mean corpuscular volume (MCV) 2
• Iron studies (serum ferritin, iron, total iron binding capacity) help confirm iron deficiency as the cause of anemia 2
• Imaging studies (transvaginal ultrasound, saline infusion sonohysterography, or MRI) can determine fibroid location, size, and relationship to the endometrial cavity 1

Management Approaches

• Treatment should address both the anemia and the underlying fibroid-related bleeding 2

• For anemia correction:

  • Oral iron supplementation for mild to moderate anemia 2
  • Intravenous iron for severe anemia, poor oral absorption, or when rapid correction is needed 5, 6
  • Blood transfusion may be necessary for hemodynamically unstable patients or those with extremely low hemoglobin levels 4

• For controlling fibroid-related bleeding:

  • Hormonal therapies:
    • Levonorgestrel intrauterine system (IUD) provides excellent menstrual suppression 7
    • Combined oral contraceptives decrease menstrual blood loss 7
    • GnRH agonists or antagonists can reduce fibroid volume and induce amenorrhea 1
    • Selective progesterone receptor modulators (SPRMs) like ulipristal acetate can control bleeding and shrink fibroids 1
  • Surgical interventions:
    • Hysteroscopic myomectomy for submucosal fibroids 3
    • Abdominal myomectomy for multiple or larger fibroids 1
    • Hysterectomy as definitive treatment for women who have completed childbearing 4

Prevention Strategies

• Early identification and treatment of heavy menstrual bleeding in women with fibroids 5
• Iron supplementation for at-risk women, particularly those with known fibroids and heavy menstrual bleeding 5
• Use of hormonal contraceptives to reduce menstrual blood loss in women with fibroids 7
• Regular monitoring of hemoglobin levels in women with symptomatic fibroids 2

Common Pitfalls and Caveats

• Underestimating the severity of anemia in ambulatory patients who appear clinically stable despite critically low hemoglobin levels 4, 3
• Failing to address both the anemia and the underlying cause (fibroids) in the management plan 2
• Delaying definitive treatment in women with recurrent or severe anemia due to fibroids 3
• Overlooking patient education about the relationship between fibroids, heavy bleeding, and anemia, which may lead to delayed care-seeking 3
• Not considering IV iron as an alternative to blood transfusion in stable patients with severe iron deficiency anemia 5