Hormonal Imbalance
Incidence
This article on the effect of hormones on constipation, or how hormones may be the causes of constipation, is mostly directed at women. It has been reported that around 40% of women in their second trimester of pregnancy experience constipation, and 20% in their third. The population, on average, reports 10-20% incidence of constipation.
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There are two theories which ascribe the causes of constipation to particular biological features of women. In the first theory, hormonal changes change something in the gastrointestinal tract causing more difficulty in passage of stool. In the second theory, mechanical changes of the gastrointestinal tract due to a gestating embryo lead to difficulties in evacuation. However, it seems that if the incidence of constipation is higher in women in the 2nd trimester, when the fetus is smaller, the hormonal theory has slightly more credence.
The latest research
To explore this idea, researchers have looked at variables are that are
potentially causes of constipation as to whether they are strongly correlated
with constipation in women in a non-pregnant state. For example, it has been
noted that before puberty, constipation is more common in boys but after puberty,
the increased incidence is found in girls.
In the same vein, researchers have looked at how hormones released during the
menstrual cycle have an impact on gastrointestinal transit times and can
serve as the causes of constipation. The subjects were imaged with
advanced medical equipment to show how food moves through the
colon. However, these studies revealed very little difference in passage time
between women at different phases of the menstrual cycle. Such studies,
unfortunately cannot be replicated in pregnant women because the imaging methods
require ingestion of slightly radioactive substances that are harmless to
adults but possibly damaging to the fetus.
Sex hormones
Because the effects of hormones may be too subtle in non-constipated women, studies have also turned to look at whether women with severe constipation have abnormally high levels of sex hormones. Sex hormones have been implicated as causes of constipation. Several sex hormones were followed throughout the menstrual cycle for two groups of women, normal and those afflicted with severe primary constipation. In this study, it was confirmed that while women with constipation have reduced steroid hormones. However, the researchers of the felt that the results could have been an artifact of how the hormones are broken down and may have instead been the effect rather than the causes of the constipation.
Inconclusive
Finally, some researchers have found that statistically women with constipation
are more likely to have undergone gynecological surgery. To explain this,
one scientist suggested that the same hormones are causes of constipation for gynecological
problems could be driving constipation. But further study revealed no links.
Most recent studies are also inconclusive.
In summary, although there are some tantalizing bits of evidence that levels of
homrones affect constipation, no study has confirmed the link. The only evidence
for hormonally driven constipation are the two observations that women suffer more from constipation,
and women in pregnancy experience a marked increase in constipation in their second
trimester.
Sources:
Cullen and O'Donoghue, Constipation and Pregnancy, Best Practice & Research Clinical Gastroenterology, 2007, 21(5), 807-818 Muller-Lissner et al, Myths and Misconceptions about Constipation, American Journal of Gastroenterology, 2005, 100:232-242