Help on reaction dopamine with sodium hydroxide

Why 1 mol of dopamine can react with 3 mols of sodium hydroxide to form a salt?


It has 2 OH groups per formula that could react with NaOH to give a salt. The NH2 group being basic would not react. I can only think that it is 1 mole dopamine to 2 moles NaOH. Cannot see how 3 moles would be needed