Endometriosis in Men: Rare but Possible
Both in scholarly literature and within popular magazines and online forums, instances of men grappling with endometriosis are recurrently discussed. However, it is noteworthy that endometriosis is often regarded as a “mysterious female disease” and a “misunderstood female condition” .
Moreover, the term “endometriosis” and the description of the ailment as “cells akin to the lining of the uterus” may inadvertently reinforce the notion that only individuals possessing a uterus can experience this condition. This begs the question: How is it possible for men to also be afflicted by endometriosis?
Background: Understanding Endometriosis?
Endometriosis is a medical condition characterized by the growth of tissue formations resembling the uterine lining outside the confines of the uterine cavity. These growths, known as endometriosis lesions, can manifest within the pelvic region, extend throughout the abdominal cavity, and even emerge on unexpected sites such as the diaphragm, lungs, or brain. Within Germany, approximately 1.7 million women grapple with this ailment. Notably, around 10% of women in their childbearing years experience the effects of endometriosis, rendering it the second most prevalent gynecological disorder .
In essence, these cellular accumulations initially proliferate and subsequently disintegrate and bleed if conception does not transpire. However, the inability to expel this blood from the body, a scenario unlike the uterine endometrium, can lead to the development of cysts, inflammation, or scar tissue.
- What endometriosis is and the various theories about its development.
- How common endometriosis is in men.
- The possible explanations for the occurrence of endometriosis in men.
- How endometriosis in men can be treated.
- Why women should also inform themselves about the topic of endometriosis in men.
Causes: The Theories Behind Endometriosis Development
Despite the significant number of affected women, the exact causes of endometriosis remain uncertain. Currently, the consensus is that a combination of triggering factors contributes to the development and manifestation of the condition. However, none of the existing theories can comprehensively elucidate the complexity of endometriosis development.
Transplantation or Implantation Theory 
This theory suggests endometriosis arises from retrograde menstruation, where menstrual blood containing endometrial cells enters the abdominal cavity via the fallopian tubes. However, given that a large percentage of women experience retrograde menstruation, this theory fails to account for the full extent of endometriosis cases. It also does not explain lesions in unusual locations, such as the lungs, and brain, in women without a uterus, and even men. Therefore, the search for other mechanisms of origin continues.
Coelom Metaplasia Theory 
This theory proposes endometriosis develops from cells lining coelomic cavities during embryonic stages. It could clarify lesions occurring beyond the urogenital tract, but it does not align with the prevalence of endometriosis solely among women.
Induction Theory 
Building upon Coelom Metaplasia, this theory suggests endometriosis lesions originate from undifferentiated cells (stem cells). However, animal studies offer only partial validation for this hypothesis.
Embryonic Residue Theory
This theory asserts endometriosis originates from Müllerian ducts, embryonic precursors of sex organs. While it explains endometriosis in men, it does not account for lesions outside the urogenital tract.
Theory of Tissue Injury and Repair 
The uterus’ peristalsis causes micro-injuries and ensuing tissue inflammation, stimulating repair. Estrogen released during the process sustains peristalsis, potentially leading to the invasive growth of endometrial cells beyond the uterine cavity.
Lymphatic and Vascular Dissemination
This theory posits that blood and lymphatic pathways transport endometrial cells to distant parts of the body. However, it does not address why men can also experience endometriosis.
None of the existing theories comprehensively explain the multifaceted nature of endometriosis. Further research is crucial to unravel this complexity. Hormones, particularly estrogen, are undoubtedly pivotal in endometriosis development and manifestation.
Endometriosis in Men: Is it a Possibility?
There exists a viewpoint in the literature that interprets “endometriosis” narrowly, suggesting that the term should not apply to men due to its association with the uterine lining or “endometrium” .
Certainly, endometriosis lesions can manifest in males as well as females who lack a uterus. Furthermore, given the ongoing uncertainties surrounding the underlying causes of endometriosis, attempting to oversimplify its definition would be misleading. This becomes evident when considering that the occurrence of endometriosis in individuals without a uterus offers valuable insights into the intricate developmental mechanisms in women. This knowledge has the potential to refine the treatment strategies for endometriosis.
This rationale underlies the experts’ adoption of the term “uterine lining-like cells” when referring to endometriosis. This updated terminology underscores the broader scope of the condition’s occurrence, beyond anatomical distinctions, and underscores the significance of its diverse presentations.
Classifying Documented Cases: Various Scenarios
The documented cases of endometriosis in men are relatively scarce. This could stem from the fact that the ailment predominantly affects women or from an overall lack of awareness surrounding its potential occurrence in men, leading to delayed or missed diagnoses. Just as diagnosing women can sometimes take over 12 years, the same delay might be even more pronounced among men .
These documented cases can be grouped into distinct scenarios :
Men Undergoing Hormone Therapy:
A couple of cases involved men who were receiving estrogen treatment for other conditions, subsequently experiencing symptoms attributed to endometriosis. Conversely, another instance featured anti-estrogen therapy followed by an endometriosis diagnosis
Elevated Estrogen due to Liver Cirrhosis:
Liver cirrhosis, often resulting from alcohol misuse, can lead to hormonal imbalances, including increased estrogen levels . This, in turn, might contribute to the development of endometriosis in men.
Obesity, a risk factor for endometriosis in men, is believed to raise estrogen levels . Given estrogen’s pivotal role in endometriosis development, this could explain why severely obese men experience this condition. A documented case highlights a 54-year-old man with endometriosis focus in the bladder.
Intersex Individuals with Both Male and Female Reproductive Organs
Intersex individuals encompass those whose genetic sex does not align with their biological sex, or those with ambiguous genitalia or the presence of both female and male reproductive organs. In the latter scenario, an individual might outwardly present as fully male but possess both a functional uterus and ovaries . An instance is documented involving a 21-year-old male who, while encountering lower abdominal discomfort linked to premenstrual dysphoric syndrome (PMDS) symptoms, was identified through an MRI scan to possess a uterus and ovaries alongside external male genitalia.
Transgender Men after Gender Reassignment
Transgender men are individuals who were assigned female at birth but identify and live as men. This identity may involve hormone therapy, surgery, or both to align their external appearance with their gender identity. Although their outward appearance may resemble cisgender men, it is essential to note that some transgender men retain their uterus and ovaries, even after gender-affirming surgeries.
Symptoms: What are the Symptoms of Endometriosis in Men?
Managing endometriosis in men is challenging due to the limited number of documented cases. Consequently, a comprehensive list of symptoms associated with endometriosis in men remains elusive.
Nevertheless, the following symptoms have been observed:
- Localized pain at the sites affected by endometriosis lesions.
- Abdominal pain.
- Presence of blood in the urine, with or without pain.
- Experience of discomfort before and during what would correspond to “menstruation” (in intersex men).
Treatment Approaches: How is Endometriosis Treated in Men?
Treatment strategies employed in documented cases to alleviate or address the symptoms of endometriosis encompass the following components:
- Surgical removal of the endometriosis lesions.
- Hormonal therapy or cessation of hormonal supplementation.
- Surgical excision of the uterus and ovaries in the case of intersex men.
- Weight reduction for individuals with severe obesity.
Debunking Myths Surrounding Men and Endometriosis
- Endometriosis only affects those with a uterus: Tissue sample studies have unequivocally shown that endometriosis lesions can develop in men. Additionally, women who have undergone a hysterectomy are not exempt from developing endometriosis. The condition’s name should not limit its definition, as it was coined at a time when diagnostic capabilities were more limited.
- Endometriosis is exclusively a women’s issue: This notion is flawed. The understanding that endometriosis can also affect men is crucial for gaining valuable insights into the condition’s development. Such insights have the potential to benefit affected women significantly, as a comprehensive understanding of endometriosis extends to all genders.
While endometriosis is primarily associated with gynecological issues, there are documented cases of men affected by the condition. The hormone estrogen seems to significantly influence the development and manifestation of endometriosis, even in males. Integrating insights from these cases into research could lead to a deeper understanding of the condition’s causes, potentially enabling more effective causal treatments instead of solely symptom relief.
- Andreas D. Ebert; Endometriose, Ein Wegweiser für die Praxis; De Gruyter
- Gynäkologie und Geburtshilfe, Springer Verlag, 2006