At first glance Primobolan seems like it would be a great option to boost the effects of TRT while also helping control estrogen. However, its use can be very detrimental to your lipids and liver health, even in low doses. It is for these reasons that its use is illicit in the US (DEA Schedule 1) and all other countries except Spain and Turkey. Even in those countries it is not to be used for longer than 3 months at a time.
There are safer ways of managing estrogen (adjusting dose and/or frequency, AI’s, etc) so using Primobolan long term to control estrogen or to boost libido is not recommended.