The blood tests are a very good way of finding out how well your are absorbing your HRT and it is useful to know what level of oestrogen you need to reach in order to fire on all cylinders. It is also good to know how oestrogen interacts with other things like thyroid function and cholesterol. For example, when I was using oral HRT/patches, I didn't feel anything like as good as I should and looking back at my blood test results, I can see that my oestrogen levels were way too low and my thyroid function (all of them) and cholesterol levels were not as good as they are now on a higher level of oestrogen.
If you are using testosterone, again, it is good to know that you are taking the right amount and seeing how well you absorb it.
I guess this is why Professor Studd wants his patients to have them.