Endometriosis is a common gynecological condition that affects millions of individuals of reproductive age globally. This chronic disease is characterized by the presence of tissue similar to the lining of the uterus, called the endometrium, growing outside the uterine cavity. These misplaced growths, often referred to as lesions, most frequently occur on the ovaries, fallopian tubes, and the tissues lining the pelvis. Because the condition is often misunderstood, confusion often arises regarding its origins and transmission. This article offers clarity on the nature of endometriosis, addressing a common misconception and detailing the currently accepted biological hypotheses for its development.
Clarifying the Transmission Myth
Endometriosis is absolutely not a sexually transmitted disease (STD) or a sexually transmitted infection (STI). The condition is a tissue disorder, meaning it involves the growth of a person’s own cells in an atypical location, and is not communicable.
A sexually transmitted disease is caused by a transmissible pathogen, such as a bacterium, virus, or parasite, that spreads primarily through sexual activity. Endometriosis, however, is a non-communicable, complex condition that develops internally and is currently linked to genetic, hormonal, and immunological factors within the individual.
The confusion may stem from the fact that certain STIs, like those that cause Pelvic Inflammatory Disease, can cause overlapping symptoms such as chronic pelvic pain or pain during intercourse. However, the underlying mechanisms of the two conditions are fundamentally different. Endometriosis cannot be “caught” from a partner, and a person’s sexual history or activity has no bearing on its development.
Leading Theories of Development
Since endometriosis is not caused by an infection, research focuses on several biological theories to explain how endometrial-like tissue appears outside the uterus.
The oldest and most widely recognized hypothesis is the theory of Retrograde Menstruation. This theory suggests that during menstruation, some menstrual blood containing viable endometrial cells flows backward through the fallopian tubes and into the pelvic cavity. These displaced cells then attach to the outer surfaces of organs, such as the ovaries and peritoneum, where they implant and begin to grow. While this backward flow occurs in a large proportion of menstruating individuals, only a fraction develop endometriosis, suggesting a person’s immune system or genetic makeup must also permit the cells to survive and proliferate.
Another prominent hypothesis is the Coelomic Metaplasia theory, which proposes that cells lining the pelvic organs possess the ability to transform into endometrial-like cells. Hormonal or inflammatory signals could potentially stimulate these cells to undergo metaplasia, which is the transformation of one mature cell type into another. This theory helps account for rare cases of endometriosis found in individuals who have not yet started menstruating or in locations outside the pelvic region.
More contemporary research also includes the Induction and Stem Cell Theories. Stem cell theory suggests that certain stem cells, potentially originating from the endometrium or bone marrow, are transported to ectopic sites where they differentiate into endometrial-like tissue. Furthermore, an individual’s genetic profile and a dysfunctional immune response are increasingly recognized as factors that may allow the initial implantation and subsequent growth of these lesions.
Recognizing Symptoms and Diagnosis
The symptoms of endometriosis can vary widely among affected individuals, ranging from entirely absent to severely debilitating. The most frequent complaint is pelvic pain, which often includes painful, sometimes disabling, menstrual cramps known as dysmenorrhea. This pain may begin before and extend beyond the menstrual flow, often worsening over time.
Other common manifestations include chronic pelvic pain that persists throughout the month, and pain during sexual intercourse, medically termed dyspareunia. Individuals may also experience painful bowel movements (dyschezia) or painful urination (dysuria), particularly during their menstrual period. Endometriosis is also a frequent finding in individuals experiencing infertility.
Due to the nonspecific nature of the symptoms, diagnosis can often be significantly delayed. A healthcare provider will initially evaluate symptoms and conduct a physical examination, often utilizing imaging techniques like transvaginal ultrasound or MRI to look for signs such as ovarian cysts or deep lesions.
However, the current standard for definitive diagnosis remains a minimally invasive surgical procedure called laparoscopy. During this procedure, a surgeon can visually inspect the pelvic organs and often obtain a tissue sample to confirm the presence of endometrial-like tissue outside the uterus.