<Not hormone. Brain states.>
The during sleep the brain largely disables the ability to make muscle and limb movements in order to protect us. It also transitions from a wakeful state to a dreaming state and vice versa. Normally this transition happens quite rapidly.
When the transition is not rapid, the brain mixes up the real world, dreams, and perhaps 'sleep paralysis' state. This mixed state gets perceived as 'wakeful dreaming', where dreams and real world get mixed. Sleep paralysis is where we awaken but are unable to move or speak. Reports of alien abductions, alien probing, secubus etc. are also products of these wakeful/dreaming states.
These experiences are quite common among the normal healthy population. They have no association nor reflection on mental illness. Once you know what they are, this knowledge should make them less frightening.
There is excellent information on the web. Key words are: Sleep Paralysis, Hypnopompic / Hypnogogic hallucination.
(note: allthough they are called 'hallucinations they have no relation to psychotic states and psychiatrists are not concerned about them)