The other thing that is really important is that the use of Utrogestan is now common yet it was not used in the vast majority of research papers. There was some research recently in the press where they number of women using Utrogestan in the trial was 58 compared to hundreds of 1000s on the old types of progestin.
This is true, but Utrogestan doesn’t feature largely in recent studies because it is relatively new. Essentially, the first generation of women using this type HRT are the guinea pigs. So risk is unknown until enough women have been taking it long enough to track whether there is any increased risk of breast/ovarian cancer and if so, whether it is less, more or the same. It is designed to be less risk, but only time will provide the proof.
This is not uncommon. Super sized tampons were sold and used by women for a few decades...and studying them using it is what revealed the risk for TSS. And then tampon size was regulated down to avoid vast majority of the TSS risk in response.
High dose contraceptive pills caused blood clots and stroke deaths in women....learnt by studying the first adopters and seeing what happened to their health. So now we have lower dose contraception called “mini pill” when first introduced, but now all pills are technically mini pills.
HRT is no different. They are adjusting it based on studies of real women using it to make is safer and safer. But each generation is the guinea pig for the next generation. Not saying this is good or bad, it is just reality, we are lucky that HRT is safer than it was, but also our experiences will help make it even safer for our daughters.
So yes, as with many things in life they are a moving target of (usually) continuous improvement.