The essential information you need to know if you have been diagnosed with an underactive thyroid

Have been diagnosed with an underactive thyroid, you are taking your thyroid hormone medication, and you are still feeling terrible?  Perhaps you are wondering if there is more you can do to start feeling even 1 percent better?  

I want to tell you, yes, there is a lot more you can do.  Solving the challenge of why your thyroid is underactive can be complex and challenging, but not impossible.  You can feel great again.  You can have energy again.  You can lose that stubborn weight you have picked up because of your underactive thyroid.

It is doable.  Simple, but not always easy.  

And it starts with having a fundamental understanding of the basics of thyroid health.  This page is that information.  The essential information you must know if you struggle with hypothyroidism.

Let’s get started. 


Hypothyroidism is a medical condition when you don’t have enough thyroid hormones in your blood for your body to function normally.  [1]

Hypothyroidism is also referred to as an underactive thyroid. 

Many people (and doctors) refer to hypothyroidism as an underactive thyroid gland, meaning that the thyroid glad is not producing enough thyroid hormones for what your body needs.  This is a little too simplistic.

You can experience hypothyroidism for many reasons.  These may include:

  • Thyroid removal (partial or whole)
  • Treatment for hyperthyroidism (overactive thyroid)
  • Iodine deficiency
  • Autoimmune thyroid disease, including Hashimoto’s
  • Hormone imbalance
  • Pregnancy
  • Certain medications and treatments (such as radiation)
  • Stress (yes, stress may contribute to hypothyroidism)
  • Disorder of the pituitary or hypothalamus glands

Symptoms of an underactive thyroid

Every cell in your body needs thyroid hormones to function.  If your cells don’t get the right number of thyroid hormones, it can impact just about every cell and system in your body.  

There are more than 100 symptoms of hypothyroidism.  Here are the most common symptoms of hypothyroidism:

  • Unexplained weight gain
  • Struggling or unable to lose weight
  • Slower metabolism
  • Fluid retention (edema) – excess accumulation of salt and water
  • Chronic fatigue
  • Long recovery/rest time after exercise
  • Aches and pains all over the body
  • Facial puffiness (aka moon face)
  • Inability to think clearly
  • Struggling to concentrate
  • Constipation
  • Heartburn
  • Bloating
  • Low or no libido
  • Menstrual disturbance – irregular or missed periods
  • Sensitivity to cold
  • Cold hands and feet
  • Hair loss
  • Dry hair
  • Brittle nails
  • Acne
  • Tinnitus
  • Insomnia
  • Waking up feeling tired
  • Depression
  • Mood changes
  • High cholesterol
  • High blood pressure
  • Dizziness
  • Frequent infections

Thyroid Anatomy

The thyroid gland lies in the center of your neck, in front of the windpipe (trachea).  It has a left and right lobe and looks like the shape of a butterfly.

The thyroid is a gland.  The main function is to produce thyroid hormones and calcitonin. 

The thyroid gland consists of thyroid follicles, which are responsible for hormone production. Within these follicles, there are:

  • Protein, called thyroid globulin (abbreviated TG), which is needed to make thyroid hormones,
  • Enzymes, called thyroid peroxidase (abbreviated TPO), that helps with making thyroid hormones.

The thyroid gland also needs iodine, a mineral that we need to obtain through our diets, to make thyroid hormones. 

Thyroid Hormones

The thyroid gland produces mainly two thyroid hormones:

  • T4 hormones are called this way because it consists of four iodine molecules,
  • T3 hormones are called this way because it consists of three iodine molecules.

The thyroid gland produces mainly T4 hormones, and a tiny number of T3 hormones.  

The T4 hormones are inactive, meaning that our cells cannot use them.  You can almost think about it as a storage hormone.   

The T3 hormones are the active hormones that our cells can use, for things like energy production and other metabolic functions.  Just about every single cell needs T3 hormones!
Our bodies do an amazing job of converting T4 hormones into T3 hormones.  This conversion process happens mainly in a few places in our bodies:
  • The thyroid gland,
  • The liver,
  • The kidneys, 
  • and the gut.
This is why a healthy body is so important, so that the hormones can be converted from the inactive T4 hormones to the active T3 hormones.  If you have problems with your thyroid gland (like Hashimoto’s or part or whole of your thyroid gland has been removed), or liver is sluggish or you have gut issues (like leaky gut), you can have T4 to T3 conversion issues (therefore, you have enough T4, but not enough T3). 
Thyroid Hormone Transport
The thyroid hormones must also be transported throughout your body.  The thyroid hormones catch a ride on a protein in your blood called TBG (thyroid-binding globulin).  
When the thyroid hormones are attached to TBG, it is called “bound”, and the cells cannot convert these hormones or use these hormones.  Only when the thyroid hormones are not attached to the TBG, they are called “free”, and can the cells use it.
The level of TBG in your blood must be just right.  Too many TBG, and the thyroid hormones are bound and not made available, and you could experience hypothyroid symptoms.  Then, if you have too little TBG, the thyroid hormones cannot catch a ride to be transported, and you again can experience hypothyroid symptoms!  
There are several things that can impact the level of TBG in your blood, including too high estrogen, too high testosterone levels, sluggish liver (where TBG is produced) [2], certain medications and illnesses.  

The Feedback Loop

How does the thyroid gland know how many thyroid hormones it must produce?  This is where the feedback loop comes in.

The hypothalamus monitors the T4 levels in the blood.  

  • If the T4 levels are too low, it sends a messenger hormone (called TRH – thyroid-releasing hormone) to the pituitary gland to tell the pituitary gland that the thyroid hormone production should be increased. 
  • The pituitary gland then sends another messenger hormone (TSH – thyroid stimulating hormone) to the thyroid gland instructing the thyroid gland to make more thyroid hormones. 

While this is a very simplistic explanation of how the feedback loop works, it is important to understand how it works.

Off course, the opposite can also occur: if your T4 levels are too high, then your TRH and TSH levels will be low, to tell your thyroid gland to make fewer thyroid hormones.  This is actually called Grave’s Disease (when you have a low TSH and high thyroid hormone levels). 

Read more about hypohthyroidism


  1. https://www.thyroid.org/hypothyroidism/
  2. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/thyroxine-binding-globulin