Endometriosis is not a sexually transmitted disease (STD). This common, chronic gynecological condition affects approximately 10% of women and individuals assigned female at birth during their reproductive years worldwide. The disorder involves the growth of tissue similar to the lining of the uterus, known as the endometrium, in locations outside of the uterine cavity. Its causes are not fully understood, but its presence has no connection to sexual activity or infectious agents.
Why Endometriosis is Not a Sexually Transmitted Infection
Sexually transmitted infections (STIs) are diseases caused by specific infectious agents, such as bacteria, viruses, or parasites, which are passed primarily through sexual contact. Examples include chlamydia, gonorrhea, and human papillomavirus (HPV). Endometriosis, in contrast, is a tissue disorder classified as a non-communicable, chronic inflammatory condition. It is not caused by any pathogen transferred during intercourse. Its development is an internal biological process, involving hormonal, genetic, and immunological factors, and it has been diagnosed in individuals who are not sexually active.
Understanding Endometriosis
Endometriosis is characterized by the presence of endometrial-like tissue implanted outside the uterine cavity. This misplaced tissue, often called lesions or implants, responds to the hormonal cycle by thickening and attempting to shed monthly, just like the uterine lining. Since the blood and tissue have no exit route, this process causes internal bleeding, inflammation, and the formation of scar tissue and adhesions.
Lesions are most commonly found in the pelvic region, including the ovaries, fallopian tubes, the outer surface of the uterus, and the ligaments supporting the uterus. Less common sites include the bladder, bowel, or distant locations like the diaphragm or lungs. The inflammation and scarring caused by this cyclical process lead to the condition’s most recognized symptoms.
The most frequent complaints include chronic pelvic pain, painful and heavy menstrual periods (dysmenorrhea), and pain during or after sexual intercourse (dyspareunia). Endometriosis is also a significant cause of infertility, affecting an estimated 30% to 40% of women who experience difficulty conceiving.
Current Theories on How Endometriosis Develops
The exact cause of endometriosis remains unknown, but several theories attempt to explain how the tissue becomes misplaced and thrives outside the uterus. The most widely accepted hypothesis is Retrograde Menstruation. This theory suggests that during the menstrual cycle, some menstrual blood containing endometrial cells flows backward through the fallopian tubes into the pelvic cavity, where the cells implant and grow.
However, retrograde menstruation occurs in most menstruating individuals, yet only a fraction develops the condition, indicating that other factors must be involved. Another theory, Coelomic Metaplasia, proposes that cells lining the pelvic cavity transform into endometrial-like tissue. This theory helps explain rare cases of the condition in individuals without menstrual cycles.
Other contributing factors include immune system dysfunction and genetic predisposition. The immune system may fail to recognize and destroy the misplaced cells, allowing the lesions to establish themselves. Familial studies show that women with a first-degree relative who has endometriosis have a significantly increased risk of developing the condition.
Diagnosis and Management
Diagnosis begins with a thorough review of the patient’s symptoms and medical history, followed by a pelvic examination. Imaging techniques, such as transvaginal ultrasound or magnetic resonance imaging (MRI), can help identify larger lesions, such as ovarian cysts called endometriomas, or deep infiltrating disease. However, these imaging methods cannot reliably detect all types of endometrial implants.
Definitive diagnosis traditionally requires laparoscopy, a minimally invasive surgical procedure. This allows a surgeon to visually inspect the pelvic organs and take tissue samples for biopsy. Many guidelines now support starting treatment based on clinical suspicion and symptoms without immediate surgical confirmation to reduce diagnostic delays.
Management strategies focus on relieving pain and slowing the growth of the lesions. First-line medical treatments involve pain relievers and hormonal therapies. Hormonal options, including combined oral contraceptives, progestins, or GnRH agonists, work by suppressing the menstrual cycle and shrinking the hormone-responsive tissue. Surgical management involves excising or ablating implants and adhesions, which may be necessary when medical therapy fails or when the disease causes significant organ damage or infertility.