Quite often endometriosis patients are told to have their ovaries removed or put their activity on hold with hormonal medication as a way of treating the disease. As demonstrated by some studies, endometriosis lesions have the potential to produce their own oestrogen, as such removal of ovaries or temporary menopause will have little or no impact on the endometriosis itself.
What is oestrogen?
Various laboratory studies have shown that endometriosis is an oestrogen dependent disease. In females, the highest quantity of oestrogens is produced in ovaries. It is also produced in small amounts in other organs such as liver, heart and brain. The oestrogen is divided in three categories: E1 known as estrone, E2 known as estradiol and E3 known as estriol.
Out of all 3 oestrogen types the E2 is the most potent and it is active during the fertility period. E1 is more potent after the menopause and it is synthesised in adipose tissue from adrenal dehydroepiandrosterone, whilst E3 has a role in pregnancy, it’s produced by placenta during pregnancy, and it is the least potent one.
What is aromatase?
The conversion of androstenedione and testosterone E1 and E2 is done by the aromatase. Aromatase is expressed in places such as the brain, gonads, blood vessels, adipose tissue, liver, bone, skin, and endometrium. In fertile women the oestrogen biosynthesis takes place in the ovary, while in postmenopausal women it takes in extraglandular tissues such as adipose tissue and skin.
The role of aromatase expression in endometriosis
One of the first studies that have demonstrated the presence of aromatase expression in endometriosis implants was published in 1996.
To demonstrate the presence of aromatase in endometriosis implants, the scholars have conducted a study analysing and comparing biopsy samples from:
- endometriosis implants from pelvic peritoneum (posterior cul-de-sac, bladder, and anterior cul-de-sac);
- endometrial tissue in patients with histologically documented pelvic endometriosis;
- pelvic peritoneal distal and normal endometrial tissues from women without endometriosis;
Based on the results, P450arom transcripts were detected in all endometriosis implants.The highest presence of P450arom was detected in endometriosis implants that involved the full thickness of the anterior abdominal wall. Also, in the core of the endometriosis implants, the P450arom transcript level was 4-fold higher than that in the surrounding adipose tissue. The authors concluded that the possibility of oestrogen production in endometriosis implants might promote their growth.
Other studies have also demonstrated a higher expression of aromatase in endometriosis implants. Zeitoun KM et al. concluded that molecular aberrations can impact the oestrogen biosynthesis leading to an increased local concentration of E2. The aberrant expressed aromatase in the endometriotic stromal cells converts C19, steroids to oestrogens.
Moreover, a immunohistochemical analysis found that the local estrogen production by aberrantly elevated aromatase takes place only in endometriosis and adenomyosis, and not in the normal endometrium.
In conclusion, removal of ovaries to stop the production of oestrogen as a way of treating endometriosis is not an efficient method, especially if endometriosis lesions are not removed. Endometriosis produces its own oestrogen and as long as the disease is left beyond it will continue to cause symptoms and impact organs.