If the side effects from Finasteride (or Dutasteride) is caused by elevated estrogen levels, then sure, taking exogenous testosterone could help. But by taking testosterone, you will also create more DHT in the body (some of exogenous testosterone will convert to DHT, you are not blocking all the enzymes. So what's the point in taking Fin/Dut to lower DHT if you are going to increase it again by going on gear? By taking exogenous testosterone you are fast-tracking your hairloss.