Researchers from the University of Oxford examined 19,889 women who were admitted to hospital for gallbladder operations over a six-year period.
They found that HRT users were 1.64 times more likely to be admitted for gallbladder disease than non-users.
The rate of gallbladder operations was twice as high among women taking HRT pills compared with women using the patches.
Two out of every 100 women taking oral HRT required gall-bladder removal.
The researchers propose that women who use HRT patches have a lower risk of developing gallbladder disease than women using the pills by allowing lower doses of oestrogen to be absorbed through the skin and into the bloodstream without being broken down by the liver.
The researchers conclude that over a five-year period, if 140 women currently taking HRT pills change to patches then this would mean one fewer gallbladder removal operation.
BMJ Online 2008
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