What is Serotonin? Part I

Orthopaedic & Spine Center
Dr. Jenny Andrus

Jenny L. F. Andrus, MD

You may have heard or read about serotonin and its role in the regulation of depression and mood in the human brain. However, this miracle neurotransmitter and hormone plays an important role in quite a few brain functions and bodily functions.  When it is well balanced, we typically feel good.  If not, then things can go a bit haywire.  In this series of articles, I will discuss serotonin, what it is, how it works, what it does in the body and what we know about it to date.  I will also discuss how serotonin is of interest to physicians who treat pain because of the role it plays in modulating our emotions, understanding, mood, and sensation.

In an earlier article, I discussed how there were three types of neurotransmitters: modulatory, excitatory, and inhibitory, all of which were important in communicating between nerves, cells, hormones, and glands.  Serotonin is a modulatory neurotransmitter in that it helps to regulate, or “tweak” other neurotransmitters up or down as is needed, depending on whatever situation we find ourselves and what our brain needs our body to do.

Surprisingly, about 90% of the serotonin in our body is produced by cells in our intestinal tract and only 10% is manufactured in the brain.  Serotonin is comprised of components such as L-tryptophan – the essential amino acid you get from eating Thanksgiving turkey or drinking milk.  Essential amino acids can only be gotten from foods we consume.  The L-tryptophan must interact with two enzymes to form 5-Hydroxytrytophan, which then can be converted into serotonin.

Serotonin plays a key role in these bodily functions:

  • Regulation of body temperature
  • Influences memory and learning
  • Mood
  • Cognition
  • Sleep
  • Sexual Desire
  • Bone Health
  • Nausea
  • Wound Healing
  • Digestion
  • Suppresses hunger
  • Aids in blood clotting

As you can see, serotonin is a busy neurotransmitter with all those functions going on!  In my next article, I’ll discuss these functions in more detail and the role they can play in chronic pain.  Later, I’ll discuss the latest research on serotonin and how it may impact pain treatments in the future.