Causes of Heavy Periods / Menstrual Flow

Menstrual flow is the result of the complex interplay of many factors that arise from the central nervous system, the pituitary gland, the ovary, the uterine muscle, and its lining. Regulation of menstrual flow is also dependent on a normally functioning clotting system. The specific evaluation of a problem for a particular woman will often depend on the duration of the problem, the age of the woman, her specific medical history, her physical exam, and her ultrasound examination. Occasionally, the cause of a particular menstrual abnormality is complex and arises from abnormalities of pituitary, adrenal and ovarian function.

Diagram of an Endometrial Polyp

The causes of various menstrual disorders can be summarized as follows:

A. Hormonal Causes

  • Pituitary gland problems
  • Thyroid gland abnormalities
  • Adrenal gland abnormalities
  • Ovarian dysfunction

B. Clotting Abnormalities

Clotting abnormalities may be responsible for 5% of cases of abnormally heavy menstrual bleeding. Women with clotting abnormalities generally have a history of easy bruisability or excess bleeding from relatively minor cuts and scrapes. Additional abnormalities might include:

C. Anatomic Problems

About 25% of women with heavy menstrual periods have one of the anatomic reasons listed below. In our practice, the most common anatomic reason for heavy menstrual bleeding is uterine fibroids, which account for the majority of “anatomic problems” that cause abnormally heavy menstrual bleeding. A summary of “anatomic problems” include:

  • Uterine Fibroids (these benign tumors originate from the uterine muscle)
  • Polyps (these originate from the uterine lining)
  • Adenomyosis (lining tissue of the uterus is found within the muscle of the uterus)
  • Decreased uterine contractile strength
  • Endometrial cancer
  • A uterus with a large surface area

There are several important things to remember about “anatomic problems” that cause abnormally heavy periods. First, uterine cancer accounts for less than 1% of these. Although cancer is among the causes of abnormal uterine bleeding it is rare in women under the age of 50 and, if caught early, is a very curable disease. Second, once your health care provider has determined that you don’t have cancer the treatment is generally one of choice rather than necessity.

Though this may be obvious to your physician or nurse practitioner it bears repeating that the majority of women in their 30’s and 40’s who have periods that are heavy because of anatomic reasons, do not have cancer. For most women it is at least comforting to know that however inconvenient or disabling their symptoms may be, it is the rare woman with heavy periods that has uterine cancer.


Diagram of Multiple Leiomyomas

The uterus contains two types of tissue—an inner lining (endometrium) that sheds each month with your period and the muscular portion (myometrium).Both of these tissue types can develop growths. When the lining tissue develops growth, they’re called polyps. When the overgrowth of muscle tissue causes tumors, they are referred to as myomas (or fibroids). Fibroids mostly produce two types of symptoms: abnormal uterine bleeding and infertility (although other symptoms occur less frequently). Many women with fibroids don’t have symptoms and the majority of them can simply choose to live with these benign tumors. Fibroids, as you can see from the drawing, can grow anywhere in the uterus. In general, the closer a fibroid is to the center of the uterus (the inner cavity) the more troublesome they become—causing heavy menstrual bleeding and infertility (or miscarriages).


Diagram of Endometrial Polyps

Endometrial polyps, though not as common as fibroids, are a significant cause of heavy menstrual bleeding. In addition, they are often the cause of post-menopausal bleeding (bleeding which occurs one or more years after menopause) as well as intermenstrual bleeding (bleeding that occurs between menstrual cycles). On ultrasound they may sometimes be confused with fibroids.

What’s the difference between fibroids and polyps?

Remember that the uterus contains 2 types of tissue—muscle tissue and tissue which lines the inside of the uterine cavity. Both of these tissue types can cause benign “tumors”. Fibroids originate from muscle tissue while polyps (also called ‘endometrial polyps’) originate from lining (endometrial) tissue.

Do endometrial polyps cause cancer?

Although endometrial polyps are generally benign they can be associated with malignancy—particularly in older, postmenopausal women. The only way to know for sure is to remove them and send to a pathologist for testing. This is routinely done.

D. Medications & Supplements That Cause Menstrual Disorders

There are a variety of medications that can cause menstrual disorders. These include:

E. The “Apparently” Normal Uterus

The vast majority of women we see with abnormal uterine bleeding have what appears to be a “normal looking” uterus—which is to say that there’s no evidence of fibroids, polyps, hyperplasia or cancer. Additionally, these women turn out to have normal thyroid functions, normal clotting abilities and no evident “hormonal” problem. So why do these women bleed heavily?

This is a complex and compelling issue. Medical logic tells us that if there’s a problem, we need to find the cause in order to treat it. In theory that would be intellectually and scientifically rewarding but life and medicine are imperfect. It turns out that often the diagnostic procedure may be more uncomfortable than the problem or the treatment.

Here are two examples:

Diagram of a uterus with Adenomyosis

There are a substantial number of women who have a uterine abnormality called adenomyosis. Adenomyosis is a disease in which there are pockets of uterine-lining tissue (endometrium) buried within the muscular wall (myometrium) of the uterus.

These are normal glands in an abnormal place. Adenomyosis is a specific type of endometriosis. Unfortunately, it is difficult to diagnose without surgery. In fact, the diagnosis of adenomyosis is often made after hysterectomy. Today we have other methods to diagnose adenomyosis but they still involve at least some surgical biopsies. The point is that there are other ways to treat women with suspected adenomyosis and avoid biopsies altogether. Some of these methods are as simple as a low-dose oral contraceptive or a hormone containing intrauterine device (IUD). Therefore, in situations where the diagnosis is more invasive than the treatment it’s wise to treat rather than biopsy—it’s less invasive, risky and costly.

A second example is one that is rarely written about—the uterus that doesn’t function normally. We know that after childbirth, some women bleed heavily and even hemorrhage because of the failure of their uterus to properly contract. Immediately following childbirth, the uterus is often massaged in order to stimulate its contraction. In many cases medications are administered that have similar effects. Apparently, strong uterine contractions are necessary to limit blood loss after childbirth. One can also postulate that some women experience heavy periods as a result of their uterus’ inability to adequate contract. In this example, the uterine may look normal (even microscopically) but doesn’t function normally. There’s no way to test for this problem yet it too can be treated with minimally invasive approaches. Some recently published work even suggests that the “aging” uterus may contain small arteries that lose their ability to contract and therefore control bleeding.

F. Miscellaneous Causes of Abnormal Bleeding

There are other uncommon and even rare causes of abnormal uterine bleeding. Some of these include:

  • Cervical cancer
  • Uterine infections
  • Severe liver or kidney disease
  • Rare ovarian tumors
  • Unsuspected pregnancy
  • Miscarriage
  • Acute emotional stress
  • Obesity

G. Polycystic Ovarian Syndrome (PCOS)

Polycystic ovarian syndrome (PCOS) is one of the most common endocrine (hormonal) abnormalities of women in their reproductive years (ages 13 – 45) and affects 6 – 15% of women worldwide.

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