Serotonin is produced naturally in the brain.

        Prozac inhibits the re-uptake of serotonin in the synaptic gap. This
means that there is more serotonin remaining longer in the synaptic
gap.
        Prozac is prescribed, as indicated, for Adult Attention Deficit Hyper
Activity (ADHD). For the Adult ADHD, this means that they do not find it
so hard to concentrate on reading, are able to enjoy relaxing moments
longer, nor feel that there are a million things that they have to do
right now!
        There is no chemical interaction between thyroxin and Prozac. Remember,
when you take a thyroid supplement, you are normalizing the function of
the thyroid.
        As for Prozac, it's action and reaction depends on the individual and
must be prescribed by a physician, who will monitor your well being.
        I hope that I haven't been to brief.
Brenda Nichols, M.A.
        I hope that I have helped you to understand a little about Prozac. One
does not effect the other nor is there a chemical interaction.