Researchers finally cottoned on in 2002 - and years after the fact - that HRT was dangerous, and that its risks outweighed any benefits.
These risks were most famously highlighted in the Women's Health Initiative Study, which discovered that HRT increased the likelihood of heart problems by 29 per cent, stroke by 41 per cent, and breast cancer by 26 per cent. The researchers were so alarmed by their findings that they stopped the study early.
As a result, HRT drug sales plummeted, and companies such as Pfizer and Wyeth, which both manufacture leading HRT brands, suffered. Sales of Wyeth's Premarin family of HRT drugs fell sharply from around $1.25 billion in 2003 to $880 million a year later.
Now, for whatever reason, the same research team recently decided to take a fresh look at its own data - and decided that HRT is good for you. Yes, they'd got it wrong, silly them. Actually, HRT decreases the risk of heart disease by 24 per cent, and it didn't increase the risk of stroke at all.
HRT advocates like Dr John Stevenson were incensed. He said the original findings meant that women were deprived of a great drug, and so went on to suffer heart attacks and other illnesses that "they didn't deserve". Obviously, those who did deserve one got what was coming.
So, cause for much celebrating in the boardrooms of Pfizer and Wyeth - well, for a week anyway.
Then, to spoil the party, a new study, rush released by The Lancet on the web, has found that HRT is bad for you after all, just as the original Women's Health Study had found. The Million Women Study has discovered that the drug causes ovarian cancer, and that at least a thousand women in the UK alone have died from the disease as a direct result of using the therapy.
Overall, HRT increases the risk of ovarian cancer by 20 per cent, the researchers found, and a woman who takes HRT has a 63 per cent greater risk of developing either ovarian, breast or endometrial cancer.
This tallies with the earlier finding that HRT has been directly responsible for the deaths of 30,000 women in the UK, and around 200,000 in the USA, since the early 1990s.
(Sources: Journal of the American Medical Association, 2007; 297: 1465-77 (revised Women's Health study); The Lancet, 19 April 2007, published online (Million Women study)).
E-news broadcast 20 April 2007 No.352 [Subscribe]