What is serotonin primarily recognized as?

Serotonin is primarily recognized as a type of neurotransmitter. It plays a crucial role in transmitting signals between nerve cells in the brain, impacting a variety of functions such as mood, sleep, and appetite. This classification as a neurotransmitter indicates its role in facilitating communication within the nervous system.

While serotonin does indeed have implications for mood regulation and can be associated with hormonal functions, its primary identity is that of a neurotransmitter. This is what differentiates it from the other options, which may highlight specific characteristics or functions of serotonin but do not capture its primary role in neurochemistry.