for intercourse, and it's usually not something mechanical during intercourse that causes the change.
Likewise the lack of enough estrogen during puberty or maybe even the change that occurs after menopause can be a cause for pain.
Not Fully Estrogenized:
In some women, the hymen doesn’t become
fully estrogenized or elasticized during puberty. One healthcare provider
who does premarital exams told us that she sometimes prescribes estrogen
cream for her abstinent patients who are getting married whose hymens
haven’t become very elasticized yet. So if you haven’t had intercourse and
are concerned, this would be a good question to ask a gynecologist—Does
your hymen appear to have been adequately
estrogenized for intercourse?
(As for the effect of hormonal birth control on the hymen, no one knows.
No research has been done.)
In the newborn the hymen is vascular and the epithelium is thick.
In the prepubertal female, the lack of estrogen renders the
hymenal tissue thin and friable.
Therefore, there is no distensibility prior to puberty.
At puberty, it becomes thick and
redundant with a tendency of folding out
...
At menopause, the epithelium becomes thin in response to estrogen depriva-
tion
http://www.thehealthj.com/december_2012/hymen_facts_and_conceptions.pdf
Vaginal atrophy, also called atrophic vaginitis, is thinning, drying and inflammation of the vaginal walls due to your body having less estrogen. Vaginal atrophy occurs most often after menopause, but it can also develop during breast-feeding or at any other time your body's estrogen production declines.
For many women, vaginal atrophy makes intercourse painful — and if intercourse hurts, your interest in sex will naturally decrease. In addition, healthy genital function is closely connected with healthy urinary system function.
http://www.mayoclinic.org/diseases-conditions/vaginal-atrophy/basics/definition/con-20025768
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