AUB-L – When is the leiomyoma the culprit?

Blog Post by Malcolm G. Munro MD, FACOG, FRCS(c), Professor, Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Director of Gynecologic Services, Kaiser Permanante, Los Angeles Medical Center, Los Angeles, CA, USA

I frequently am approached by surgically ambitious residents (registrars) with a pitch that goes something like this:

“I have a 47 year old patient with menometrorrhagia from a 13 week size symptomatic fibroid uterus who wants a hysterectomy. When can we do it?”

Typically the patient hasn’t been adequately investigated as the assumption is that the leiomyomas (fibroids), detected with some combination of manual examination and ultrasound are indeed the cause of the abnormal bleeding – this, coupled with an irrational exuberance for surgery, results in a patient who “wants” a hysterectomy. So what is wrong with this story?

In the United States, at least, by the age of 50, leiomyomas are present in almost 70 per cent of Caucasians and more than 80 per cent of women of African ancestry. (1) Since most of these women don’t have any symptoms, an astute observer should conclude that most “fibroids” are asymptomatic. So when the symptom of abnormal uterine bleeding (AUB) occurs in a woman who can be demonstrated to have leiomyomas, the clinician should be challenged to distinguish AUB that is caused by the myomas from that which occurs for other reasons. Those familiar with the varied causes of AUB in the reproductive years, detailed in FIGOs new classification system, will recognize that there are a large number of potential entities, both structural, and those unrelated to visible pathology, that could coexist with asymptomatic leiomyomas and be the actual cause of the abnormal bleeding.(2) So, you might ask, if that is the case, which leiomyomas contribute to AUB and which do not?

To answer this, we should look to the FIGO system, which has a subclassification for leiomyomas. When a woman presents with AUB and is found to have one or more submucous leiomyomas (Types 0, 1, & 2), she is categorized as having AUB-Lsm; if the endometrial cavity is normal, meaning that none of the leiomyomas distort the cavity by deviating the endometrium (Types 3-8), she is categorized as having AUB-Lo (“o” standing for other leiomyomas or those outside the endometrial cavity). While we need more well-designed studies, the present hypothesis is that the leiomyoma likely must directly contact the endometrium for the lesion to contribute to the AUB; in other words, the leiomyoma must be submucous in location, a circumstance that can be noted in the FIGO system as “AUB-Lsm”.

What is the evidence for such a relationship? Until recently, most of the evidence was indirect, with studies showing that removal of submucous leiomyomas resulted in the predictable improvement in the symptom of heavy menstrual bleeding. However, more recently, we are beginning to assemble the molecular puzzle, as it is apparent that leiomyomas manufacture factors such as TGF-Beta3 that can impact the endometrium, if it is nearby, by interfering with the action of the unlikely substance bone morphogenetic protein (BMP), that adversely impacts some of the mechanisms involved in local control of menstrual bleeding.(3) It takes little imagination to see that if the leiomyoma is remote from the endometrium, such an impact would be reduced or eliminated altogether.

So when we interview the resident’s patient with a structured history, we frequently find that indeed the patient has the irregular bleeding typically associated with an ovulatory disorder (AUB-O) and, despite the presence of Type 4 and 5 leiomyomas, evaluation with office hysteroscopy, contrast sonography or MRI, demonstrates a normal endometrial cavity. In such instances, the endocrine etiology of the problem is amenable to a host of medical interventions including combination oral contraceptives and cyclical or continuous progestins – and, such patients may even have a discernable and treatable cause of the anovulation, ranging from hypothyroidism, obesity or personal stress. Alternatively, the hysteroscopy or contrast sonography might identify a polyp or smaller Type 0 or 1 lesion that can be removed easily, often in the office. So the patient’s options are frequently are far more numerous than hysterectomy, and often safer and relatively painless. So just because you find leiomyomas in a woman with AUB, doesn’t mean that the two are related – taking the time to critically evaluate all the potential contributors to the symptom of AUB may relieve your patient from the unlikely notion of “wanting” a hysterectomy.

More about AUB-L can be found in the book Abnormal Uterine Bleeding, from Cambridge Medical Press.(4)

1. Day Baird D, Dunson DB, Hill MC, Cousins D, Schectman JM. High cumulative incidence of uterine leiomyoma in black and white women: ultrasound evidence. Am J Obstet Gynecol. 2003;188:100-7.
2. Munro MG, Critchley HO, Broder MS, Fraser IS. FIGO classification system (PALM-COEIN) for causes of abnormal uterine bleeding in nongravid women of reproductive age. Int J Gynaecol Obstet. 2011;113:3-13.
3. Sinclair DC, Mastroyannis A, Taylor HS. Leiomyoma simultaneously impair endometrial BMP-2-mediated decidualization and anticoagulant expression through secretion of TGF-beta3. The Journal of clinical endocrinology and metabolism. 2011;96:412-21.
4. Munro MG. Abnormal Uterine Bleeding. Cambridge: Cambridge University Press; 2010.

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