Hello, because tamoxifen has a good effect, but its selectivity is low and it is easy to produce side effects. Many drugs are like this. The effect of treating a certain disease is good, but some drugs have side effects because of their low selectivity. When taking drugs, we should first choose drugs with small side effects and effective ones, but if the drug effect has not improved obviously, we can only choose drugs with side effects. This is the process of taking medicine, and some side effects are inevitable, so we can only treat them symptomatic!