Do some temperaments have specific neurotransmitters and/or hormones that are more "active"?
According to a study by Dr. Helen Fisher et. al., YES!

This could be neurotransmitter, hormone review; research review; brain scan review or fit into personality unit

Students take 4-temperament quiz to discover one of four temperaments

Fisher Temperament Inventory and Tie Breakers. Each question received a score of 0–3 for Strongly Disagree, Disagree, Agree and Strongly Agree.

Dr. Helen Fisher et. al performed fmri on TWO GROUPS - each looked at pictures of familiar person who was neutral AND pictures of loved one
Group #1: Long-term love group (self-reported happy marriage with average of 21 years)
Group #2 Newlywed group (either engaged/pre-married couples or newlywed partnerships w/ average of approximately 4 years)

external image journal.pone.0078734.g001&representation=PNG_M

A-D. Dopamine-rich substantia nigra region activation (arrows), shown in an axial image, was correlated with Curious/Energetic scores

E.–H. The ventrolateral prefrontal cortex activation (arrows), shown in a coronal image, was correlated with Cautious/Social Norm Compliant scores. Dr. Fisher predicted this might be correlated with serotonin-rich brainstem, but it was not, as had been concluded in other studies.

I.–L. The dorsolateral prefrontal cortex activation (arrows, BA10), shown in a sagittal image, was correlated with Analytical/Tough-minded scores.
There was also activity in the occipital cortex, which mediates basic visual functions. These results are consistent with the prediction that this temperament dimension is influenced by testosterone...

M.–P. The inferior frontal gyrus activation (arrows), shown in a coronal image, was correlated with Empathic/Expressive scores. The
fusiform gyrus is associated with mirror neurons and empathy. Empathy is regularly associated with estrogen activity.