The body uses chemical messengers to communicate between the various tissues in order to meet the energy needs of the body, facilitate development and address the demands of the environment. Most people are familiar with this concept through their understanding of endocrine hormones, such as testosterone, growth hormone or insulin. There are many other messenger chemicals present in the body…some familiar, some strange and exotic sounding. Neurotransmitters travel from nerve to nerve in the brain or the body. Similarly, many cells release paracrine and autocrine hormones that are rarely spoken of outside of science journals or research labs.

Endocrine hormones travel through the bloodstream to affect tissues distant from where they were produced. Paracrine and autocrine hormones stimulate receptors on cells located nearby, even stimulating the same cell in the case of autocrine hormones. A major class of hormones that seems to encompass properties of all three types of hormones is the cytokines. The number of known cytokines is fairly large and continues to grow as new discoveries are reported. One that is most well studied is called interleukin 6 or IL6.

Many cytokines are called interleukins because they are used by the immune system to stimulate inflammatory cells called leukocytes. However, as is being (slowly) understood by clinical scientists, most hormones are not tissue-specific. In other words, hormones do not affect just one tissue— for example, testosterone does not affect just skeletal muscle, but also the sex glands, skin, fat cells, blood cells, brain, heart, etc. This is also the case with IL6. However, IL6 differs from testosterone in one important way. Whereas testosterone is produced (primarily) only in the testes, IL6 is produced in a variety of tissues and cells.1