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I stayed in a girls' hostel last year and I realized that me & my girl gang's menstrual cycle got synced. :D We would be PMS-ing together (or were going to be) & have the same dates as each others. Although it was a fun time, we shared our 'period probs', would understand each other better, help each other if something was troubling us, but this question remained with me. I tried looking for an answer but got too complex answers. Could anybody please help me with this query? :)

asked Oct 05 '13 at 07:24

April_Blossom's gravatar image


Synching of menstrual cycles

The observation that good friends especially sharing academic courses and living in hostels together, often get synchronized cycles is well known to gynae-endocrinologists. The phenomenon has got a lot to do with the hypothalamus which is a part of the brain that deals with emotions and co-ordinates various physical and emotional inputs. It in turn influences the anterior pituitary gland which in turn controls ovaries and thus menstrual cycles. The reason why a lactating woman ejects milk even if she hears her baby cry on the telephone, is due to the hypothalamus acting on the pituitary gland.

The synchronization of menstrual cycles in girl sharing the same courses, lectures and living conditions and probably the same groups of friends and enemies and the frenemies are expected to have a similar input in their hypothalamii which in turn will influence the pattern of release of FSH and LH which come from the anterior pituitary and which influence ovary to develop follicles and influence ovulation. If the ovulation is synchronized, it stands to reason that their menstrual cycles will be synchronized because 14 days after ovulation, cometh your period if you are not pregnant.

Further Explanation

The observation of synchronized cycles also points us towards our evolutionary progress and differences from the broad class of mammals to which we belong.

Only human beings and a few higher primates experience the phenomenon of menstrual cycles. Mammals (e.g. dogs, dolphins, elephants) which share the breast feeding behavior with human beings but do not have the phenomenon of menstrual cycles like the more evolved human beings. Different species vary the way their pituitary and ovaries and uteri work together -however to give a simple example dogs (bitches) have "estrus cycles" or period of "heat". At a particular times in the year the bitches will be on "heat" which is their estrus cycle. Their hormones change so do their vaginal secretions which in turn makes male dogs take interest in them. Dog owners will know this phenomenon and behavioral changes in their pets –dogs or bitches. The arrangement is quite suitable for these lower species as it optimizes the reproductive cycle with the availability of food. Technically the estrus cycle of all bitches is "synchronized" and that’s got largely to do with the season which decides availability of food. The pineal gland is largely responsible for this pattern in animals. This gland is however "vestigeal" (useless) in human beings and it's role ill explained.

So in some ways synching of cycles is not mystery though its mechanism is not completely explained. It’s also humbling to be reminded of our evolutionary origin.


answered Feb 09 '14 at 00:16

Dr%20Bhide's gravatar image

Dr Bhide

I have also experienced synchronising of cycles with a close female friend when living together. This is most likely due to pheromones (body chemicals released through the skin and in sweat). Pheromones signal to others our states of health, emotion, sexual arousal (often you can smell them when your partner is aroused) and genetic compatibility. Close family members pheromones will be unpleasant, most likely, and a compatible partner's personal scent will often be arousing.

There is probably a biological reason for synchronising cycles (a benefit to the group if all females within it are fertile at the same time), as well as the social advantages you mentioned in your question. It is very interesting when it happens to you!


answered Oct 11 '13 at 10:14

Mischa's gravatar image


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Asked: Oct 05 '13 at 07:24

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Last updated: Dec 13 '15 at 04:21

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