At what age can endometriosis typically start in females of reproductive age?

At What Age Does Endometriosis Start?

Endometriosis is diagnosed during the reproductive years, with symptoms typically beginning in adolescence—often at or shortly after menarche—though formal diagnosis is frequently delayed until adulthood. 1, 2

Age of Symptom Onset vs. Diagnosis

The distinction between when endometriosis begins versus when it is diagnosed is critical:

• Symptom onset: Approximately 50% of adolescents with endometriosis report pain starting at menarche itself, compared to only 33% of adults diagnosed later 3
• Age at diagnosis: The median age at diagnosis is 63 years for endometrial cancer (not endometriosis), but for endometriosis specifically, diagnosis typically occurs during reproductive years, with 4% of endometrial cancer patients diagnosed before age 40 1
• Diagnostic delay: Symptoms begin an average of 2 years before diagnosis in adolescents and 5 years before diagnosis in adults, with most women consulting 3 or more clinicians prior to diagnosis 2, 3

Epidemiology by Age Group

Endometriosis affects up to 10% of reproductive-aged women globally (9 million women in the US), and approximately 47% of adolescents presenting with pelvic pain have endometriosis 1, 2, 4:

• The disease is definitively diagnosed during reproductive years, with the annual incidence being 12.5 per 10,000 person-years among women aged 15-49 years 5
• Only 4% of women with endometriosis are younger than 40 years old at the time of formal diagnosis 1
• The prevalence during reproductive years ranges from 1% to 4%, depending on disease duration 5

Clinical Presentation in Adolescents vs. Adults

Adolescents present with distinct symptom patterns that should raise clinical suspicion:

Pain Characteristics in Adolescents

• Earlier menarche and longer menstrual periods compared to adults 4
• More severe dysmenorrhea that lasts longer and has higher pain scores 4
• Pain onset at menarche in 50% of cases (vs. 33% in adults) 3
• Chronic pelvic pain (CPP) is more common and often described as "confined" and "oppressive" rather than "widespread" 4

Atypical Symptoms More Common in Adolescents

• Nausea accompanying pain (69% in adolescents vs. 53% in adults) 3, 4
• Headaches are significantly more frequent 4
• Noncyclic pelvic pain is prevalent, with 50% reporting relief after bowel movements 3
• Higher analgesic use compared to adults 4

Risk Factors Associated with Earlier Onset

Key risk factors that predispose to endometriosis include 2, 6:

• Younger age at menarche
• Shorter menstrual cycle length
• Lower body mass index
• Nulliparity
• Congenital obstructive müllerian anomalies (such as obstructed hemivagina)

Critical Clinical Pitfalls

Do not dismiss adolescent pelvic pain as "normal menstrual cramps"—90% of individuals with endometriosis report moderate-to-severe pelvic pain that interferes with work/school, daily activities, exercise, and sleep 2, 3. The average 2-5 year diagnostic delay and consultation with 3+ clinicians before diagnosis represents a significant failure in recognizing this disease early 2, 3.

Do not wait for surgical confirmation before initiating empiric treatment—current guidelines support clinical diagnosis based on symptoms, physical examination, and imaging (transvaginal ultrasound or MRI), with laparoscopy reserved for definitive treatment rather than diagnosis 7, 2.

Do not assume imaging or physical examination must be abnormal—normal findings do not exclude endometriosis, as superficial peritoneal disease is poorly detected by all imaging modalities 7, 2.

Implications for Screening and Prevention

For women with Lynch Syndrome (hereditary nonpolyposis colorectal cancer), surveillance for endometrial cancer (not endometriosis) should begin at age 35 years with annual gynecological examination, transvaginal ultrasound, and aspiration biopsy 1. However, this recommendation pertains to endometrial cancer screening in high-risk populations, not routine endometriosis screening.

For stroke prevention, screening for a history of endometriosis is reasonable in adults, as endometriosis increases stroke risk by 34% (HR 1.34,95% CI 1.10-1.62), with vascular risk factor evaluation and modification recommended 1.