There seems to be some concern about the keto diet and thyroid function (due to recent research suggesting a connection between the two). But does the keto diet actually impact your thyroid function in a negative way?

Read on to learn all about thyroid hormones, why there are so crucial for weight loss, and what you can do to ensure your thyroid function stays healthy while on the keto diet.

What is the Thyroid Gland?

The thyroid gland is a modestly sized gland made up of two lobes that sit at the base of the front neck (just below the larynx/Adam’s apple) and run along the trachea. The two lobes of the thyroid gland are connected by the isthmus (a small band of thyroid tissue).

During the neonatal phases of child development, the thyroid is actually situated at the back of the tongue and slowly migrates towards the front neck prior to birth.

In exceptionally rare instances, the thyroid doesn’t migrate away from the tongue, or it migrates all the way down to the sternum.

How Does the Thyroid Gland Work?

The primary role of the thyroid gland is to utilize iodine – an essential mineral that you must obtain through diet and supplementation – to synthesize thyroid hormones: thyroxine (T4) and triiodothyronine (T3).

Thyroid tissue contains the only cells in your body that are capable of absorbing iodine. Within thyroid cells, L-tyrosine (an amino acid) and iodine are used to create T4 and T3.

Your thyroid gland is regulated by a tiny gland that sits at the base of your brain, known as the pituitary gland. The pituitary gland is like a control center for stimulating the production of a multitude of hormones in your body.

In healthy humans, when T4 and T3 drop too low, the pituitary gland secretes thyroid-stimulating hormone (TSH), which then signals to the thyroid gland that the body needs more thyroid hormones.

Inversely, if your body produces a large amount of T3 and T4 (or you take T3/T4 medication), your pituitary will pick up on this and reduce TSH production. (This is known as a negative-feedback loop, and is how much of the human endocrine system works.)

In many ways, your pituitary gland is like an internal thermostat, and the thyroid gland is like the heater/furnace. But the system gets even more intricate…

The pituitary gland is under control of the hypothalamus – another gland in the brain that produces TSH-releasing hormone (TRH).

As you likely derived, TRH signals the pituitary gland to produce TSH. As such, you can think of the hypothalamus like a person who actually changes the thermostat.

In reality, though, you can’t physically control your hypothalamus on a whim like you can an actual thermostat; but, you can eat certain foods and nutrients that might help encourage healthy thyroid production (which we will touch on soon).

What Thyroid Hormones Do Physiologically

Thyroid hormones are like fire logs being tossed into a furnace, as they are a major regulator of metabolic rate, body temperature, and affect nearly every cell in the human body.

A healthy thyroid gland produces about four times as much T4 as it does T3, but physiologically, T3 is about 20-fold more potent than T4 and is thus considered the “active” thyroid hormone (most T3 in your blood derives from T4).

Your body also makes T2 and T1, but they are merely byproducts and precursors of T3/T4 and appear to serve little biological value.

Naturally, if your feeling cold (despite warm weather) or vice versa, your thyroid may be producing too little T4/T3 (hypothyroidism) or too much T4/T3(hyperthyroidism).

What Is Metabolism?

Remember, thyroid hormones are a primary controller of your metabolism. But what exactly is metabolism on a physiological level? It seems like so many people view metabolism as a sort of speed-determining catch-all term that describes how much energy you burn.

In truth, that’s only a small part of what constitutes metabolism. 

Every life form on Earth is made up of one (or many) cells. Yes, this means that microscopic organisms like yeast and bacteria are living, as well as plants.

Humans and other higher mammals are a bit more intricate than lower life forms because of encephalization and having an enormous number of cells (100s of trillions in humans).

In cellular biology, molecular reactions are continuously taking place and either using or giving off energy (heat/calories) in the process.

These metabolic reactions are classified as either catabolic or anabolic; catabolic reactions release energy by breaking down complex substrates, whereas anabolic reactions consume energy to synthesize cellular components and molecules. 

For instance, we talk a lot about glycolysis here on BioKeto – which is the break down of glucose to form energy. Glycolysis is an example of a catabolic metabolic pathway in humans. Muscle protein synthesis, on the other hand, is an anabolic pathway.

Hence, metabolism is essentially the summation of every molecular reaction that happens in cells, and these reactions are necessary for life.

Simply put:

metabolism refers to the highly intricate system of molecular reactions occurring in cells that are essential for existence, and these reactions have a necessary energetic input and output (which is precisely why you need to eat and drink in order to survive).

Thyroid Hormones and Metabolism

Research demonstrates that thyroid hormones (especially T3) have both a catabolic and anabolic effect on protein metabolism throughout the human body.

This is a physiological fact that is actually readily perceptible among the population, as individuals with hyperthyroidism tend to be scrawny and have a hard time building muscle; individuals with hypothyroidism tend to gain body fat easier. 

Naturally, when people who have hypothyroidism start taking medication to increase their thyroid, their body temperature normalizes and they have an easier time losing weight.

Individuals with hyperthyroidism may be prescribed drugs that block thyroid hormone production, in which case they have an easier time putting on muscle/weight.

Does the Keto Diet Inhibit Thyroid Function?

A recent (2017) study investigating the impact of the keto diet and thyroid function found a small (but statistically significant) decline in thyroid-stimulating hormone (TSH) levels in children who were on the keto diet to treat epilepsy.

Naturally, the researchers concluded that the keto diet decreases thyroid function in children with epilepsy.

Now, there are a few things to consider before we assume there’s a connection between the keto diet and thyroid function. Firstly, this study was relatively small and the changes in TSH were small in the grand scheme of things.

Moreover, there’s existing research that suggests that the keto diet can actually increase thyroid hormone production due to the availability of more free fatty acids.

It’s also been shown that excessive thyroid hormone production doesn’t have any impact on ketogenesis in the liver.

Best Foods for Keto Diet and Thyroid Function

L-tyrosine, iodine, and selenium are the most crucial minerals/nutrients for healthy thyroid function. Iodine is an integral component of thyroid hormone structure, along with L-tyrosine. Selenium acts on various enzymes to control the synthesis of thyroid hormones.

As such, for keto diet and thyroid function, you’ll want to ensure you eat a few servings of any of these low-carb foods/ingredients every day:

  • Pink Himalayan sea salt
  • Kelp
  • Wakame
  • Dried seaweed
  • Cod
  • Shrimp
  • Whole eggs
  • Tuna
  • Green Beans
  • Watercress
  • Brazil nuts
  • Ground beef
  • Salmon
  • Cheese

These foods are all rich in iodine and/or selenium, along with many of them containing plenty of L-tyrosine. Eating a few servings of these select keto foods each day will help support your thyroid function naturally.

It’s also necessary to mention that you should routine have your TSH, T4, and T3 (thyroid panel) checked by your primary care physician.

If you are experiencing symptoms of hypothyroidism or hyperthyroidism, it’s best to have a doctor guide you (you should also let them know you’re on the keto diet).

Keto Diet and Thyroid Summary

The main takeaways from this article are that the keto diet doesn’t inherently seem to disrupt thyroid function in healthy people. It may slightly decrease TSH in children with epilepsy, but more data is necessary in that regard.

Also, remember that thyroid hormones are essential regulators of your metabolism. Thyroid hormones also tend to have both anabolic and catabolic effects in regards to protein metabolism. 

Remember to include both iodine- and selenium-rich foods in your keto diet for optimal thyroid function. You should be getting plenty of these micronutrients by eating a couple servings of the foods mentioned in this article each day.