Hormones are not the whole story

Over the years, there have been a number of blogs written by San Diego Zoo Global researchers discussing the study of hormones (i.e., the field of endocrinology) and how measuring hormones can tell us a lot about wildlife; both in nature and in our care. This is because hormones, in some way or another, are involved in the regulation or control of nearly all biological processes.

A single species can produce hundreds, if not thousands, of different hormones and most of them remain largely unstudied in wildlife species.

As mentioned above, hormones do many things. They are critical players in the control of growth and metabolism. Species that begin life in one form, such as a tadpole and change into another, like a frog or a toad, owe this ability to undergo metamorphosis to hormones.

Hormones are essential to reproduction and the types and levels of hormones produced differ between males and females. What specific hormones do in different species can also vary. For example, in many mammals the hormone cortisol is released when an animal experiences stress. This kick starts the biological processes needed to generate enough energy to help the animal avoid the stressful situation and allow everything to return to normal.

Cortisol also controls the stress response in fish. Yet, in fish that migrate between fresh and salt water, cortisol also helps them maintain proper salt and mineral balances in their bodies as they move between these two very different environments.

As students, we are first introduced to the concept of hormones, quite fittingly, in middle school or early high school. Each of us were likely introduced to hormones in the same way. We were all told something like this…“Hormones are chemical messengers produced in one part of the body and travel through the bloodstream to other parts of the body where they have an effect. Once they arrive, hormones bind proteins called receptors. This relationship is like a lock and a key. A single type of hormone (the key) can only bind its specific receptor (the lock). This ensures that specific hormones have very specific functions”.

This correctly highlights a critical aspect of hormone function. Without their biological accomplices, hormone receptors, hormones are not capable of doing much at all.

However, as is the often the case in biology, there are exceptions to the rule. In the case of hormone receptors, it turns out some of them can bind a whole lot more than their specific hormones, and as it turns out, this can cause problems.

It wasn’t until my sophomore year in college that I learned that there are many, many chemicals in the environment that can also interact with hormone receptors. When they do, the usually tightly controlled actions of hormones can be disrupted and the biological consequences can be profound.

In the Endocrine Lab of the Reproductive Sciences group, we specialize in studying how environmental chemicals interact with hormone receptors and interfere with reproduction. This blog is the first in a series, where we will highlight specific projects in our lab and how, by studying hormone receptors and how they interact with environmental chemicals, we are using the knowledge gained to save species.