• Dr Peter Chew

Too “Fit” To have Menses

She jogged. She ran. She worked out in the gym every day, 7 days a week.


H, a 28-year-old lawyer was an exercise buff since she was a teenager. She was also an avid runner, taking part in marathons the last 2 years.


“Doc, I am so fit physically, why has my menstruation eluded me the past 5 months?” she asked.


On further questioning, H had regular menses every month until a year ago while preparing for a marathon. She suddenly noticed that her menstrual flow was getting scanty and the cycle length was getting longer, occurring every 35 to 50 days. But she did not pay any attention as she thought it was normal. She was slightly concerned when she missed her menses for 5 months.  She was baffled as to why the menses had ceased and would like to know whether this could have any impact on her reproductive health.


H was having a medical condition called exercise associated amenorrhea (EAA) which occurs in 3 to 4 percent of women who exercise too intensely.


This condition arises when the energy expended from exercise far exceeds the caloric intake from food, a result of intense training. To conserve the available energy for other more important physiological processes, the body shuts down the function of less essential ones like those in the ovary. The brain centre (hypothalamus) which controls the ovary alters the way it releases the hormones. As a result, the ovary stops ovulation. This leads to reduced production of the female hormone(oestrogen) resulting in the cessation of menstruation.


Besides amenorrhea, EAA can lead to a reduction of bone mineral density as oestrogen is important in the metabolism of calcium. Bone fractures may occur more easily. Research studies have shown that this loss of bone mineral density may be permanent and may not be reversed once it occurs. Though the damage may be mitigated with hormone replacement treatment, the lost minerals cannot be replaced, resulting in irreversible long-term damage to bone health.


I told H that in order for her menses to resume, the following steps had to be taken:

1. She had to cut down the frequency and duration of her exercise.

2. She had to increase her caloric intake and maintain a certain amount of body fat and protein. Studies have shown that at least 16 percent body fat or more is necessary for normal menstruation.

3. She had to consume 1500 mg of calcium a day to maintain her current calcium needs. This was to reduce her likelihood of stress fractures and osteoporosis later in life.


H understood the seriousness of EAA. She started to make lifestyle changes. She began to put on weight and her menses had resumed, albeit still slightly irregular, 6 months after the consult.

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