Does the liver discard Tryptophan that the human body does not need?

[Erina]

How well is the human body's process understood if imbibing L-Tryptophan (in synthetic supplement form) that the liver will process only what the body requires to convert to 5-Hydroxytryptophan for use as serotonin?

If skipping this step and directly introducing 5-Hydroxytryptophan into the body, it surely has no chance to regulate how much it needs?