What is “amenorrhea” and why should I care about it?

“Secondary” amenorrhea occurs when the menstrual cycle either stops completely or is so slow and erratic that no more than two identifiable periods occur per year.  “Primary” amenorrhea occurs when there is no identifiable onset of menses by age 15.  Amenorrhea is just the more extreme manifestation of menstrual disorders that can occur.  A normal menstrual cycle occurs every 23 to 32 days.  Menstrual cycles can be drawn out considerably longer than this.

Cycles between 33 days and 4 months in length are labeled as “oligomenorrhea.” Cycles that are shorter than 21-22 days reflect a deficiency in the hormone progesterone, and are characterized as exhibiting a “short luteal phase.”  Women with menstrual cycle dysfunction often are not ovulating (no egg is released from the ovary in conjunction with the menstrual cycle).  Lack of ovulation is associated with low estrogen levels.  Low estrogen levels are associated with increased bone loss at a time when a young woman should be accumulating bone mass.  When low nutritional intake contributes to this problem, proper bone formation is also affected negatively.  This increases the risk for development of osteoporosis later in life.  Women with prolonged amenorrhea consistently are shown to have low bone mineral density relative to peers with normal periods. Athletes with amenorrhea also have a greater risk to develop stress fractures (microscopic overuse injuries of the bone).

What are the causes of amenorrhea?

Menstrual dysfunction can be caused by many factors, and young women with no menstrual periods by age 16, or who were formally cycling but have missed 5-6 consecutive periods, should see their physician and undergo a workup to try to determine a cause.  Some of the more common causes of secondary amenorrhea include:

•   Pregnancy

•   Ovarian failure

•   Polycystic ovarian syndrome

•   High levels of prolactin – a hormone that is released by the pituitary

•   Overactive thyroid

•   Disordered eating

As part of the initial workup, your physician will likely check several blood tests, looking for evidence that points to some of the problems on the above list.  You will also be asked questions about your dietary habits and exercise routine.  It is important to be as accurate as possible when answering these questions as they help your physician put together an accurate picture of what is going on with you.

I’ve heard that exercise can cause amenorrhea. Is that true?

Technically, no.  Athletic amenorrhea is actually caused by a calorie imbalance that occurs when there is not enough of a total calorie reserve left over for general body functions after calories burned by activity are accounted for.  We call this calorie “bank account” “energy availability,” and when energy availability is too low, the body has to start prioritizing which organ systems will get the available calories.  Usually the reproductive system is one of the first systems to be compromised.  We know that exercise itself does not cause the menstrual irregularity, since studies have shown that you can make menstrual periods go away by increasing exercise and holding diet constant, and then bring them back again by leaving the exercise level at the new higher level and simply increasing the daily dietary intake.  Thus, exercise is only an issue inasmuch as it uses calories that may be needed for other things.

I eat a pretty good diet. I don’t think I’m out of calorie balance.

This is fairly common among women who exercise regularly.  When you deny yourself calories by not eating for a long period of time, the body’s hunger reflexes are jump-started and you get the urge to eat.  When you burn calories through exercise though, there is no similar bodily reflex that signals the need to replace them.  Thus, even with good intentions and no sense of problems, you can easily get into calorie imbalances if you are not consciously replacing what you are burning off.

The problem magnifies when eating habits are truly disordered.  Patients with eating disorders have a high rate of amenorrhea, both due to their nutritional imbalance and to their low body weight, which is a separate risk.  The combination of disordered eating, menstrual dysfunction, and bone mineral density problems is known as the “Female Triad,” and is one of the reasons that sports physicians screen active women for an indication of these problems.

What is the level of energy availability that I should be striving for?

Studies have shown that women maintain menstrual regularity at energy availability levels of 30 calories per kilogram of lean body mass.  This means that a 130-pound female who is at 20% body fat needs about 1400 calories left over after all activity-related calorie usage has been accounted for.  Running 5 miles per day at a pace of 7 miles/hour burns roughly 500 calories, bringing the minimum daily calorie intake in this example to about 2000 calories/day.  Other activity interspersed throughout the day will add to the total.  Regular skipping of meals or restriction of food portions or fat calories can easily result in energy availabilities under the threshold.  An online calculator that estimates calorie burn by activity can be found at:

http://health.discovery.com/tools/calculators/activity/activity.html

How can I tell if my bone density has been affected?

Depending on the duration of the problem and your age, your doctor may want to obtain a study called a DEXA scan.  DEXA scans measure the density of your bones, and the density of your bones relates to risk of things like stress fractures during sports, or development of osteoporosis later in life.

Typically, girls have accumulated over 90% of their total bone density by age 20.  50% of your total bone mineral density is accumulated between puberty and age 18, and there is an approximately two-year window between age 12 and 14 when 25% of your total bone mineral density is obtained.  Once a woman is 25, most of her bone density is set.  This means that going forward, especially after age 30, there is a constant rate of bone loss each year that is fixed.  If the levels that were acquired in childhood are adequate, bone mineral density should stay above the threshold where osteoporosis occurs, even at an advanced age.  If the levels that were acquired in childhood are suboptimal, there will likely be a point at which bone mineral density drops below a safe threshold, and osteoporotic fractures can occur.  The goal of proper management of your amenorrhea is to avoid getting to this point. Keeping in mind that the most rapid period of bone acquisition occurs before the age of 14, menstrual problems that are noted at earlier ages should be addressed more urgently, since medical intervention may have more of an impact.

The DEXA scan needs to be interpreted differently for young women who have not yet achieved their peak bone density than for elderly women who are undergoing screening for osteoporosis.  The variables looked at on the test are also a bit different.  Only a limited number of centers have the proper equipment for this, but it is important that the test is done at a center where the technicians and interpreting physicians are used to working with the pediatric age group. After the test is done, your doctor will tell you where your bone density falls relative to where it should be for your age.  The results will help determine how you should be managed.