The Impact of Insulin on Thyroid Health: Why it Matters and What You Need to Know

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A man's hand holding a functional health blood glucose meter.

Insulin and thyroid are two essential hormones in the body that work closely together. The thyroid gland produces hormones that regulate metabolism, and the pancreas produces insulin, which regulates blood glucose.

When thyroid function is low, glucose uptake by cells decreases, causing high levels of glucose in the blood. This results in hyperglycemia and a sluggish insulin response to elevated glucose. This vicious cycle continues as the pancreas produces more insulin to compensate for the high glucose levels, leading to insulin resistance. People with hypothyroidism may also experience a decreased rate of glucose absorption in the gut and slower clearance of glucose and insulin from the blood.

While conventional medicine focuses on treating thyroid imbalances with medication, many patients continue to feel unwell. This underserved population may have insulin resistance or pre-insulin resistance, a stage before the clinical diagnosis. Practitioners should measure insulin and postprandial glucose in patients showing signs of thyroid imbalance, as these are early indicators of insulin resistance.

If you are someone who has been on thyroid medication, or you are suffering from thyroid symptoms and have been told everything is fine, this can be extremely frustrating. Symptoms like dry skin, dry hair, hair falling out, low body temperature, increased susceptibility to infections, high cholesterol, depression, and inability to lose weight may not necessarily be linked to the thyroid gland only. In fact, there may be a significant link between insulin resistance and thyroid function.

Unfortunately, this is often overlooked in mainstream medicine, leaving many people without the proper health plan they need to restore normal metabolic function.

Most western trained, allopathic doctors miss important data that can help speed up the healing process. In this article, we will explore the impact of insulin on thyroid health and why it is crucial to have your insulin levels tested.

Lab Testing for Thyroid and Insulin Imbalances

Thyroid blood tests are usually the first step in evaluating thyroid dysfunction. Unfortunately, the usual approach is to only test for TSH, Thyroid Stimulating Hormone.

In a study published in the Journal of Clinical Endocrinology and Metabolism, it was found that all participants had symptoms of thyroid dysfunction despite having “normal” Free T4 and TSH concentrations. The study emphasized the significance of glucose tolerance, insulin sensitivity, and endothelial function in relation to the thyroid in a relatively sizable population.

This particular study was the first one that actually looked at blood sugar control and endothelial function in relationship with thyroid health in a relatively large population. This shows that relying solely on TSH levels is not enough to evaluate for hypothyroidism.

6 Often Overlooked Ways Insulin impacts Thyroid Function

The way the body uses glucose for energy is one of the many metabolic processes that are controlled by thyroid hormones, and insulin resistance can result from an imbalance in thyroid hormone levels. Therefore, high levels of insulin have a major impact on thyroid function.

  1. Insulin triggers increased TSH, so elevations may not necessarily be related to the response of the thyroid gland.

  2. Insulin impacts the thyroid receptor function, so it doesn't allow the thyroid hormone to get into the cell's nucleus to perform its duties.

  3. Elevated insulin can cause a decrease in DHEA, which is produced by the adrenal glands and can inhibit thyroid function if it is too low.

  4. Insulin resistance stimulates cortisol, and cortisol impacts the T4 to T3 conversion and the sensitivity of the cell receptors.

  5. Insulin resistance triggers inflammation, and inflammation affects thyroid receptor function. Inflammation can lead to cytokines that get produced not just by high levels of cortisol, but by inflammation in the body which can impact thyroid receptor function.

  6. Insulin damages the mitochondria, and we need the mitochondria to be producing plenty of ATP for proper thyroid function.

There may be other interactions between insulin and thyroid as well, but these are the ones that are well documented, and are important to examine in people who have been to the doctor with a list of hypothyroid symptoms and are told that they are fine.

Sadly, the interaction between thyroid hormone and other hormones is often overlooked, and doctors do not typically test for high levels of insulin unless the patient is diabetic.

It’s clear from the science that testing insulin levels early in life, even when someone is 18-20 years old or getting their first health insurance exam may be a good idea, because we are not looking for low levels of insulin but for too high levels. Classically, people are in a hyperinsulinemia state for up to 30 years before the development of type two diabetes, so it is important to identify this early on.

Redefining Normal

The definition of “normal” within mainstream medicine and the tests that are used to define whether someone is hypothyroid are often not enough. 92% of the population is estimated to be in the realm of metabolically unwell, which means their insulin levels are too high, their blood sugar levels are too high, and they are experiencing the dangers and the damages that occur all before they become diagnosed as diabetic. It is important to address this population, as it is the one that can benefit from interventions that address insulin resistance.

Case Study: Reversing Thyroid Dysfunction and Insulin Resistance

Let’s look at an actual case and the amazing results one woman had in reversing Hashimoto’s after being on thyroid medication for over 52 years.

This woman, we’ll call her Sally, joined our Sweet Spot Solution program due to concerns over her glucose levels, which were starting to increase. It’s important to note that her insulin levels had not yet been tested.

She was identified as being in the pre-diabetic stage and was advised to return in six months for further assessment and potential medication for diabetes. However, the patient was not satisfied with this approach and sought help from our insulin resistance balancing program.

Following the recommendations in the Sweet Spot Solution Program resulted in normalization of her fasting glucose levels and reversal of her pre-diabetic stage. She had also been taking thyroid medication for 52 years due to a diagnosis of Hashimoto's thyroiditis.

Within four months of restoring optimal fasting blood sugar, her thyroid function normalized, and she was advised by her endocrinologist to stop her thyroid medication, and several other medications as she no longer needed them. The root cause of her thyroid dysfunction was identified as insulin resistance.

Conclusions About How Insulin Impacts Thyroid Function

Thyroid health and insulin are closely linked, and addressing insulin resistance is crucial for the management of thyroid-related symptoms. Even when lab tests appear normal, practitioners should look for signs of pre-insulin resistance, including postprandial glucose levels.

Thyroid dysfunction can cause a decrease in glucose uptake by cells and a slower clearance of glucose and insulin from the blood, leading to hyperglycemia and elevated insulin levels. Both hyper and hypothyroidism can lead to insulin resistance.

If you’re a health practitioner, whether functional or conventional, it’s important for you to understand the critical link between thyroid health and insulin. Do the research to help your patients.

Insulin resistance has a significant impact on thyroid function, and relying solely on TSH levels is never enough to diagnose hypothyroidism. It is crucial to test insulin, and if you detect high levels, that you address the issue before it leads to severe thyroid dysfunction. By addressing insulin resistance, you can significantly improve thyroid health and overall well-being.

If you’re a conventionally trained medical doctor, you may be thinking, “I never learned this in medical school”, so do your own research.

This is critical, and when you learn the power of helping people to get their blood sugar under control, to get them to normalize metabolic function before they become diabetic, you’ll see major improvements in people with abnormal thyroid function, and you'll be the hero in their life.

So step out there, educate people about the role of insulin in their thyroid problems. Educate them about the diet and the lifestyle and everything that they can do to turn it around. Check out my podcast episodes on thyroid for more information. There's also a series on metabolic disturbance and insulin resistance.

For a deeper dive into helping people to restore thyroid function naturally, and for more access, go to

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