Researchers from the University of Texas, studied 24,000 postmenopausal women over five years.
They found those who took hormones had a 21 per cent higher risk of getting kidney stones compared to those who took a dummy pill.
The risks were similar for women taking Prempro, pills containing estrogen plus progestin – or Premarin, estrogen-only pills.
Recent data suggest that overall, about six per cent of postmenopausal women develop kidney stones.
The kidneys remove waste products from the blood and transfer them into the ureter. Occasionally this waste can form into crystals that collect together into stone-like lumps.
They can grow to the size of golf balls and cause severe pain. If the stones block the urinary system they can cause infection and kidney damage.
Large stones are sometimes treated with noninvasive shock wave therapy or surgery.
Study leader Dr Naim Maalouf said women considering HRT to ease hot flushes and other symptoms such as mood swings should ‘look at the bigger picture,’ weighing those benefits against the risks for kidney stones.
He added that HRT has also been linked with far more serious health problems such as breast cancer and heart attacks.
The U.S government recommends that hormone replacement pills only be used to relieve menopause symptoms, in low doses for the shortest possible time.
Victoria Davis, a spokeswoman for Pfizer Inc – which took over Premarin and Prempro maker Wyeth Pharmaceuticals last year – noted that the government research was not designed to examine kidney stone risk.
The studies analysed by the researchers were designed to examine hormones’ effects on various ailments, but not specifically kidney stones. However, women were asked periodically if they’d been diagnosed with kidney stones during the multi-year studies.
The latest study appears in the Archives of Internal Medicine.
Daily Mail