# Menstruation and the Moon

**URL:** <https://boards.straightdope.com/t/menstruation-and-the-moon/38132>\
**Category:** Factual Questions\
**Created:** [October 24, 2000, 4:57pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132 "2000-10-24T16:57:18Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![JeffB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeffb/32/188_2.png) [@JeffB](https://boards.straightdope.com/u/JeffB)\
**Post date:** [October 24, 2000, 4:57pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/1 "2000-10-24T16:57:18Z")

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On NPR last night (during _All Things Considered_, I think), a writer was being interviewed. (I didn’t catch her name or what she wrote – I’m just full of details.) She said that the menstrual cycle for women who sleep outside will adjust to coincide with the lunar cycle, with the women being most fertile during the full moon (more or less). She also mentioned a connection with the pituitary gland. I didn’t hear the whole interview, so I may have missed some vital bits of information.

I saw a couple of previous threads about the connection between menstruation and the moon, but they didn’t address this. So I have two questions:

1. Are there reliable studies that show that women who sleep outside on a regular basis will have their menstrual cycles tuned to the moon’s cycle?

2. How does this happen? Is the pituitary gland involved?

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**Author:** ![scratch1300](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@scratch1300](https://boards.straightdope.com/u/scratch1300)\
**Post date:** [October 24, 2000, 5:02pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/2 "2000-10-24T17:02:38Z")

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Sounds bogus. Other placental mammals have different menstrual cycles, some longer, some shorter. And most animals sleep outside. Why don’t _they_ coincide with the moon, menstrually speaking?

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**Author:** ![LazarusLong42](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@LazarusLong42](https://boards.straightdope.com/u/LazarusLong42)\
**Post date:** [October 24, 2000, 5:27pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/3 "2000-10-24T17:27:53Z")

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1. No.

2. No. But there is some evidence that the pineal gland (near, but behind, the pituitary) does play a role in this. It may be able to sense the day/light cycle, and thus would be partially responsible for maintaining the menstrual cycle by clocking out 24 hours, and knowing when 28 days is over. There are also genes to regulate the 24-hour cycle, at least in fruit flies.

LL

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**Author:** ![aseymayo](https://avatars.discourse-cdn.com/v4/letter/a/a88e57/32.png) [@aseymayo](https://boards.straightdope.com/u/aseymayo)\
**Post date:** [October 24, 2000, 5:37pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/4 "2000-10-24T17:37:40Z")

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It doesn’t sound too likely to me. What is meant by “outside” exactly? Outside on the ground, or outside in a tent? A hut? A lean-to? If the great outdoors has such an effect, wouldn’t it happen if I just slept with the windows open?

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**Author:** ![Odieman](https://avatars.discourse-cdn.com/v4/letter/o/a87d85/32.png) [@Odieman](https://boards.straightdope.com/u/Odieman)\
**Post date:** [October 24, 2000, 6:47pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/5 "2000-10-24T18:47:38Z")

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Let’s look at what [url="[http://www.straightdope.com/columns/990924.html](http://www.straightdope.com/columns/990924.html)"Cecil has to say on the subject.  
Keith

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**Author:** ![Odieman](https://avatars.discourse-cdn.com/v4/letter/o/a87d85/32.png) [@Odieman](https://boards.straightdope.com/u/Odieman)\
**Post date:** [October 24, 2000, 6:48pm UTC](https://boards.straightdope.com/t/menstruation-and-the-moon/38132/6 "2000-10-24T18:48:59Z")

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[http://www.straightdope.com/columns/990924.html](http://www.straightdope.com/columns/990924.html)

Here’s the link above 😉  
Damn VB code.  
keith