Thyroid Part 1: Why are hormones Important

Why Are Hormones Important? 

We have all heard the debate; one side says that calories do not matter, it is all about hormones. The other preaches that only calories and macros matter and that you can eat as many pop tarts as you like and still achieve your health and fitness goals. So which is right? As usual, the answer falls somewhere in the middle and helping someone to achieve optimal health and body composition as efficiently as possible requires a working knowledge of both.

So, where do hormones fall on this continuum? While we cannot deny the law of thermodynamics when fat loss is concerned, many people do not understand the myriad of factors that influence the process. Inflammation, biogenetics, digestive health, chronic stressors, nutrient deficiencies and, you guessed it, hormones all play a role in this complex picture. While many people think that these two perspectives are diametrically opposed, in truth, our endocrine system (the system that controls the regulation of our hormones) is central to energy expenditure.

Hormones produced by the endocrine system have all sorts of roles within the body that allow us to function better, both inside and out. Whether this means we can attack the day full of energy, better manage cravings and hunger or achieve metabolic flexibility, these messengers hold a lot of power over how we look and feel.

Metabolic flexibility is “the ability to respond or adapt to conditional changes in metabolic demand”. Optimising the environment of our central nervous system and the endocrine system allows us to efficiently utilise fuel from food by switching between stored glucose and fatty acids, depending on our environmental demands. 

One hormone that has a significant influence is thyroid hormones. A common complaint by overweight individuals is that they have sluggish or “underactive” thyroid but how often is this true? While many use this buzzword as a means to explain or justify a lack of progress, the thyroid plays a role in many other areas in the body, including temperature regulation and energy production. So, how can we tell if we have a client with low thyroid output and what can we do about it? Understanding the key signs and knowing pitfalls you should avoid are two keys to achieving better results and ensuring that our clients are healthier and happier in the long term.

The Endocrine System

Before we look into the thyroid specifically, it is essential to understand the endocrine system as a whole. 

The body has two systems that gather information around the body and in turn, take action to maintain homeostasis. They can also communicate with each other to provide the response that the body needs. 

These systems are:

  1. The nervous system: It uses incredibly quick messages sent via your nerves. An obvious example is your body’s lightning-fast response to pain if you touch something hot.
  2. The endocrine system: This secretes hormones that travel through the bloodstream. It is slower than the nervous system but has widespread effects that can function for longer.

There are at least 50 different types of hormones at work at any one time within your body. They control most of your body’s daily subconscious operations, including reproduction, metabolism, growth and development and immunity, among others, to maintain homeostasis. 

The endocrine organs are situated all over the body and include:

  • The pineal gland,
  • The hypothalamus,
  • The pituitary gland,
  • The thyroid gland,
  • The parathyroid gland,
  • The thymus gland,
  • The adrenal gland,
  • The pancreas,
  • The gonads,
  • The placenta (in women).

A gland is any structure in the body that makes and secretes hormones. The glands indicated in red also fulfil functions other than hormone production. The hypothalamus indicated in blue has secondary functions for the brain. 

The pituitary gland is the master gland in the body. It secretes many hormones that trigger other glands, such as the thyroid gland, parathyroid gland, adrenal and pineal glands, to make their hormones.

How Do Hormones Work?

A hormone can only trigger a reaction in specific cells that have a specific corresponding receptor. These are known as called target cells and function similarly to a key in a lock.

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Most hormones are composed of amino acids (such as peptides or proteins) or lipids (such as cholesterol) meaning they can either be water-soluble or lipid-soluble. This is important because cell membranes are made of lipids. For a water-soluble hormone to enter a cell, it requires a receptor on the outside of the cell, such as GLUT4, which allows insulin to enter. 

In contrast, fat-soluble receptors are situated on the inside of the cell. The hormone alters the cell’s activity by increasing or decreasing some of its functions to maintain homeostasis and provide a consistent internal environment.

In addition, some hormones create what is known as a hormonal cascade. This is when certain hormones regulate the production of other hormones. If there is a disturbance to this chain of these processes, it can trigger various issues over time.

The Hypothalamic-Pituitary Axis

The location where the nervous and endocrine systems meet is an area in the brain called the hypothalamic-pituitary (or HPA) axis. The HPA axis is one of the core components of the brain, coordinating adaptive responses to stressors. It is one piece of the limbic system, a part of the brain that controls memory and emotional responses.

It communicates with the Enteric Nervous System (ENS), which controls digestion, as well as the immune system. These components form a bidirectional communication network that includes the central nervous system (CNS), the brain, spinal cord, autonomic nervous system (ANS) alongside the ENS and HPA axis. The autonomic nervous system, with its sympathetic and parasympathetic branches, carries messages from the intestinal barrier (lumen) and transmits them via the ENS, spinal cord and the vagus nerve that connects the brain and the gut4. 

The HPA axis is also where the nervous system and the endocrine system communicate and decide whether to prioritise fight-or-flight (the sympathetic nervous system) responses or rest-and-digest (parasympathetic nervous system) responses based on our environment. One of the hormones triggered by a fight or flight is cortisol.

Various factors can cause one or more of the hormones secreted by the endocrine system to become unbalanced. These can be described with the following prefixes:

  • “Hyper-“ – referring to the overproduction of a particular hormone.
  • “Hypo-“ – referring to the underproduction of a particular hormone.