Weighing in at around 20-30 gms, that butterfly-shaped gland in your neck is small enough that you probably don’t even know that it’s there. Yet, this little gland wields a mighty influence over every organ in your body. 

Metabolism is the body’s ability to convert food into energy. Thyroid hormone plays a significant role in this. You felt its effects even before you were born - thyroid hormone regulates metabolic processes essential for normal growth and development of a fetus. And this continues on throughout our life, waxing and waning through the different stages of aging. 

Thyroid hormones (T4 and T3) produce their actions by first attaching to specific thyroid hormone receptors on the surface of our cells, like a plug into a socket. These receptors are scattered throughout our body, in every organ, thus allowing for widespread action by the thyroid hormones. 

The effect of thyroid hormones are particularly well known in these aspects:

  1. Body weight and basal body temperature: Thyroid hormones increase the conversion of food into energy and increased energy expenditure. The increased oxygen consumption from metabolism also drives an increase in body temperature (thermogenesis). Hence, when a person has hyperthyroidism or high thyroid levels, they can lose weight despite an increased appetite. They may also feel hotter than usual or have increased sweating from the increase in basal body temperature. 
  2. Cardiovascular system: The effect of thyroid hormone is like blowing air onto a smoldering fire. It increases heart rate as well as makes the heart beat more forcefully (increasing the output of blood from the heart). At the same time, it also makes our blood vessels dilate to allow for increased blood flow to our organs. Revving up that engine! Too much of this is not a good thing, though, as high thyroid levels can also trigger palpitations and arrhythmias from putting a strain on the heart. 
  3. Carbohydrate metabolism: The role of thyroid hormones here is to make more fuel available to burn. By that, I mean the breakdown of food stores in the liver to make more glucose freely available to convert into energy. It also enhances the action of insulin, pulling glucose into cells for metabolism. Hypothyroidism is often associated with brain fog or a sluggish mental state which may be partly because the brain needs a steady supply of glucose to function optimally. However, too much thyroid hormone, such as Graves’ disease or hyperthyroidism can be associated with metabolic derangements, including elevated blood sugar. 
  4. Lipid metabolism: Thyroid hormones stimulate breakdown of fat molecules (lipolysis), again to provide substrate for burning energy like a fuel. A lack of thyroid hormone can cause a build up of fat cells, for example, high cholesterol levels in hypothyroidism which improve after treatment with thyroid medications such as Levothyroxine. 
  5. Adrenal support: Although your adrenals primarily make cortisol or stress hormone, which is necessary to survive, the thyroid hormone plays a role in influencing adrenal function during times of illness, fasting or starvation. During such times, thyroid hormones adapt in order to conserve the body’s energy and burn less glucose than usual, also protecting the body from further wear and tear during a vulnerable time. Nutritional feedback plays a role in the thyroid hormones influencing your adrenal glands’ output of stress hormone and lowering it to conserve energy. 

Too much or too little of anything is not a good thing. Thyroid hormones need to be perfectly balanced for all the organ systems in our body to function as they are supposed to. That’s why I often compare thyroid hormones to oil in the engine. Not too obvious at first glance but impacting overall function in so many ways!

What are some questions you have around the Thyroid / metabolism connection?

Yours in good health, 

Dr. Ashita Gupta