What could cause irregular bleeding all month long?

DEAR DOCTOR K:

My periods used to be pretty regular. But for the past few months, I’ve been spotting all month long. Why is this happening?

DEAR READER:

There are many possible explanations. Fortunately, few of them can turn into serious problems. Before talking about the causes of abnormal bleeding from the uterus, it’s worth reviewing the menstrual cycle.

Normally, the cycle is triggered by signals from sex hormones. Hormones made in the brain travel to the ovaries, leading to the production of other hormones by the ovaries: estrogen and progesterone. But sometimes the cycle’s hormonal signals get thrown off. Irregular bleeding, including alternating periods that are heavy and light, spotting, or shorter and longer cycles, can result.

In the first half of the menstrual cycle, levels of the female hormone estrogen start to rise. Among its many functions, estrogen stimulates the making of the inner lining of the uterus. This endometrial lining is the blood-enriched layer of tissue that grows inside the uterus every month to prepare for a possible pregnancy. While the lining is growing, an egg in one of the ovaries starts to mature. Midway through the monthly cycle, the egg leaves the ovary. This is called ovulation.

The egg travels from the ovary down a tube (the oviduct) to the uterus. If the egg is fertilized, it lands in the uterine lining, where it begins to grow. If the egg is not fertilized, hormone levels drop. As a result, the thickened lining of the uterus is shed during the menstrual period. This prepares the uterus to form a new and fresh inner lining a month later.

Irregular bleeding can happen for a number of reasons. In teenagers, for example, following the start of menstruation, cycles may take a few months or years to become normal. That’s often because hormone levels aren’t yet sufficient to keep the endometrial lining growing. As a result, parts of the blood-enriched lining separate from the uterus, then get passed from the uterus to the vagina. Then the pieces of lining get passed out of the vagina, which is when spotting is noticed.

Other factors that can change bleeding patterns include:

  • Hormonal abnormalities (thyroid problems, for example);
  • Medications (most commonly, birth control pills and blood thinners like warfarin);
  • Excessive exercise or weight loss;
  • Obesity;
  • Stress or illness.

Just as at the beginning of the menstrual cycle, sex hormone levels start to peter out and get irregular as a woman approaches menopause. Spotting becomes more common than earlier in life.

There are many effective treatments to help regulate periods and control irregular bleeding. If irregular bleeding is caused by another medical condition, treating that condition should restore normal cycles. Otherwise, treatment is based on the cause and the amount of bleeding.

When deciding on treatment, your doctor will take into account whether you want to have children or not. If you don’t, birth control pills that combine the hormones estrogen and progesterone can decrease the amount of bleeding. If you do, your doctor may prescribe medication to help your ovaries ovulate more regularly.