Oral contraceptives and hormone replacement therapy (HRT) may be associated with a heightened risk of developing inflammatory bowel disease, new studies suggest.
In two large cohorts, researchers found an association between oral contraceptives and Crohn's disease, but not ulcerative colitis. And a related study of postmenopausal women found an association between HRT and ulcerative colitis, but not Crohn's disease.
Researchers presented their results at the Digestive Disease Week conference in San Diego, California.
Oestrogen may be the culprit
Dr Hamed Khalili, who led the studies at Massachusetts General Hospital in Boston, said that doctors "should carefully consider contraceptive options among women with a strong family history of Crohn's disease."
As for HRT, Dr Khalili added, "As there are other cogent reasons for women to minimise use of hormone therapy, we believe our data have more mechanistic than clinical implications. Specifically, our results provide novel insights into unique biological pathways related to oestrogen that may mediate the pathogenesis of ulcerative colitis."
Dr Khalili's team drew its conclusions from data on 117 935 participants in the Nurses Health Study I from 1976 to 2008, and another cohort of 114 794 women in the Nurses Health Study II from 1989 to 2005.
Contraceptive risk for Crohn's disease?
The combined studies yielded 5 323 303 person years of follow-up, during which there were 309 new cases of Crohn's disease and 362 new cases of ulcerative colitis.
After multivariate adjustment, current users of contraceptives appeared to have the highest risk for Crohn's disease (hazard ratio: 2.66). But past users also had elevated risk (HR: 1.40).
The researchers found no significant association with ulcerative colitis, however.
To look at the effect of HRT on IBD risk, Dr Khalili's team studied 108,589 postmenopausal US women who enrolled in 1976 in the Nurses Health Study at a median age of 54, with no history of IBD. Through 2008, the researchers had a total of 1 891 153 person years of follow up, during which the women developed 138 incident cases of Crohn's disease and 138 cases of ulcerative colitis.
Multivariate analysis showed a heightened risk of ulcerative colitis among current hormone users (HR: 1.74), and a lower but still elevated risk among past users (HR: 1.68).
There was no association with Crohn's disease, however. Also, the type of hormone therapy used did not appear to affect the IBD risk.
Relevance of oestrogen receptor signalling
Dr Jerrold Turner at the University of Chicago, who was not involved in the research, said that "given that in the general population (there seems to be) a slight increase in risk, if you're already a person with a higher risk because of family history, it's not a bad idea. It's not that unreasonable."
On the other hand, he said, it's important to note there's no data in the study to support the idea that women with a family history of Crohn's disease should reconsider using oral contraceptives.
These are investigational studies and the relative risks are pretty small, Dr Turner points out. "The most important thing is that there's a potential relevance of oestrogen receptor signalling - signalling via oestrogen - to the development of inflammatory bowel disease. This is an area of further study and this gives us a toehold as a starting point," Dr Turner said.
(Reuters Health, Rob Goodier, May 2012)
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