Is it possible that a child produce too much blood serotonin, does it affect physical growth of children?

Serotonin and growth. serotonin is a neurotransmitter found in the CNS, and in other tissues as gastrointestinal tract, relation with growth hormone and growth hormone releasing hormone has long been studied, the complex interaction would ultimately affect growth, a clear simple answer to a rather complex question in simple terms cannot be given on this platform.