The Endocrine System 101

So far, scientists have identified over 50 hormones in the human body. But what are hormones, where do they come from, and what do they do?

Hormones are the chemical messengers of the body, regulating both physiology and behavior. They are created in endocrine glands, which are specialized groups of cells present within the brain and the body. Once produced in the glands, they are secreted into the bloodstream and travel through the body, binding to specific receptors, and triggering certain processes. These chemical signifiers affect and manage hundreds of bodily processes, often through a chain reaction of several different hormones. Hormones are not just within humans, or mammals, or even just animals. Hormones are found regulating functions within fungi and plants as well. Life comprises a system of atoms experiencing the effects of chemical reactions.

The endocrine system works on a feedback loop, much like the thermostat in your home, to regulate the amount of each hormone in your body. These amounts can fluctuate over the course of an hour, a day, or a lifetime, depending on the hormone’s specific function. 

Working together, the endocrine system regulates:

• Growth and physical development 

• Metabolism, digestion, and energy levels

• Reproduction and sexual function 

• Sleep and the circadian rhythm

• Behavior, stress, pain tolerance, and mood

• Homeostasis of blood pressure, blood sugar, body temperature, and fluid/electrolyte balance

For example, our sleep-wake cycle is regulated by cortisol (made from the adrenals) and melatonin (made from the pineal gland). 

Your body uses hormones for two types of communication. The first type is communication between two endocrine glands: One gland releases a hormone, which stimulates another gland to change the levels of hormones that it’s releasing. An example of this is the communication between your pituitary gland and thyroid. Your pituitary gland releases thyroid-stimulating hormone (TSH), which triggers your thyroid gland to release its hormones, which then affect various aspects of your body.

The second type of communication is between an endocrine gland and a target organ. An example of this is when your pancreas releases insulin, which then acts on your muscles and liver to help process glucose.

The endocrine system comprises the hypothalamus, pituitary and pineal glands located within the brain, the thyroid, thymus, and adrenal glands, as well as the pancreas and sexual organs, the testes and ovaries. The image below indicates where these glands and organs are located. The hypothalamus is the neural control center of the endocrine system and sits right above the pituitary gland in our brain.  

Below is a further look into the function of each major gland and organ in the endocrine system. 

• The hypothalamus links the endocrine system and the nervous system. The hypothalamus gathers information from the brain and sends it to the pituitary to release hormones.

• The pituitary gland is often called the “master gland” because the hormones it creates regulate many other endocrine glands. It also secretes endorphins that act on the nervous system and reduce feelings of pain.

• The pineal gland is light sensitive, creates melatonin and regulates the wake-sleep cycle.

• The thyroid controls that rate at which cells turn food into energy and controls the levels of calcium in our body

• The thymus creates T-cells that control immune function

• The adrenal glands make corticosteroids that control salt and water balance in the body, as well as immune and sexual function. It also makes adrenaline, which affects blood pressure and heart rate

• The pancreas makes insulin and glucagon to control blood sugar levels

• The gonads make our sex hormones. Testes in male bodies create testosterone and sperm. Ovaries in female bodies make eggs and secrete estrogen, progesterone, and a small amount of testosterone. 

The specific hormones created by each gland/organ can be found at the end of this post. Once hormones have served their function, they are destroyed by either the liver or their target organ/tissue, and then are removed by the kidneys.

Laboratory tests can measure hormone levels through blood, urine, or saliva. Even small changes in hormone levels can have large impacts on our minds and bodies, so it is important to seek a medicine professional if dealing with hormone imbalance.

Endocrine-Disrupting Chemicals (EDCs) are substances found in our air, water, soil, food, personal care products, and manufactured products that interfere with the proper functioning of the endocrine system. EDC’s function in four main ways:

• Hormone mimics: trick the body into thinking a hormone is present when it is not

• Hormone blockers: stop natural hormones from doing their job

• Hormone level drivers: affect the levels of hormones in our blood by changing how hormones are made, broken down, or stored within the body

• Body sensitivity EDCs: change how sensitive our bodies are to different hormone levels 

You can find more information about EDCs at https://www.endocrine.org/patient-engagement/endocrine-library/edcs

In future posts we will discuss more about endocrine disruptors and specific hormone functions. Please leave any questions or comments below!

Spread Joy. Be light. Choose Kindness.

Leah