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The Cold Connection to Hashimoto's Thyroiditis

Updated: Jun 12

Brown fat modulates thyroid function


  • Although most medical doctor's believe that Hashimoto's thyroiditis is a life-long, degenerative autoimmune disease, some people have reversed their Hashimoto's by adopting a practice of ice baths and ketogenic diet.

  • The mechanisms of thyroid modulation via cold water immersion therapy act through activation of brown fat (brown adipose tissue, BAT).

  • When activated by cold, BAT produces thyroid hormone that modulates thyroid function and regulates metabolism.

  • Without regular cold stimulation, brown fat disappears in the adult human body, and the thyroid can become dysregulated.

  • Restoration of brown fat via ice bath or cold plunge can restore proper thyroid function.

Hashimoto's reversal: Miracle, or science?

Most medical doctors will tell their Hashimoto's thyroiditis patients that they suffer from a chronic, degenerative, permanent autoimmune disorder that will require a lifetime of prescription medications that will fail to cure the underlying disease.

But not Dr. Courtney Hunt.

She was a Hashimoto's patient herself, until she reversed her condition with a ketogenic diet and cold plunging.

Dr. Hunt has discontinued her thyroid medications, and her health is better than ever.

By any medical measure, she is cured.

Her story, and others like hers, begs for further, scientific investigation, particularly with regard to cold water immersion therapy.

Can cold exposure reverse Hashimoto's?

The connection between hypothyroidism and deliberate cold exposure has long been a topic interest in the medical community. For example, it is well understood that patients with hypo- (under active) thyroidism suffer from cold intolerance, and it makes sense. The thyroid is something like a thermostat for the body. When we are exposed to cold, the thyroid signals our brown fat cells to begin metabolizing the energy stored in our white fat, to produce heat to keep us warm.

The process is called thermogenesis.

The problem is that in highly industrialized countries like the United States and Western Europe, technologies like central heating, a trend towards urbanization and office jobs, and a preference for thermal comfort have resulted in a population that is so rarely exposed to cold that most adults have lost nearly all brown fat -- so there's nothing left for the thyroid to signal. In fact, brown fat is so rare in adult humans living in highly industrialized setting that until the 1970's medical scientists thought brown fat was just baby fat that adults eventually grew out of. In fact, regular exposure to cold in adulthood will recruit new brown fat cells, increasing our capacity for thermogenesis.

Without brown fat, most of us experience discomfort when we're cold, partly because our bodies use the only other metabolic pathway available to keep us warm.

We shiver.

Shivering is an involuntary tremor in our muscles that is fueled by glucose from the bloodstream. Energy extracted from blood glucose is released as heat within our muscles, which may help prevent hypothermia for a short time. It's the body's emergency back up response to cold exposure when brown fat thermogenesis is unavailable.

For most modern adults, and especially those with an underactive thyroid (i.e., hypothyroidism), brown fat thermogenesis is never available, so cold exposure results in the body signaling an emergency and initiating shivering.

That's why the conventional medical advice for cold sensitivity due to hypothyroidism is to "keep your home warm," and "avoid unnecessary exposure to cold weather (Wentz, 2015). Although this is a prescription for avoiding discomfort, it may be exactly the wrong thing to do to cure Hashimoto's.

By doing the opposite of the traditional medical advice and intentionally plunging herself into a freezing ice bath several times a week, Adrienne signaled her body to recruit new brown fat cells, and cured her Hashimoto's.

Existing studies of the relationship between thyroid activity and brown fat have already established the role of thyroid hormones in activating brown fat thermogenesis. For example, the Annals of Medicine (Contreras 2014) reports that brown fat "displays a high expression of thyroid hormone receptors. In fact, thyroid hormones work synergistic with norepinephrine and are required to generate a full thermogenic response." A subsequent study (Broeders et al. 2016) showed "that higher levels of thyroid hormone are associated with a higher level of cold-activated BAT."

As a consequence of this understanding, several pharmaceutical companies have undertake to develop drugs that initiate brown fat thermogenesis for weight loss, without cold exposure. For example, a recent scientific article published in the journal Molecular Endocrinology suggests that activating brown fat metabolism is an effective mechanism for weight loss But rather than recommending regular cold exposure, the article suggests that synthetic drugs (called "pharmacological interventions") might provide the metabolic benefits without the thermal discomfort (Ahima 2016).

However, my view is that there is no need to develop a drug to do what the human body is already perfectly capable of doing for itself.

Until very recently, no one was studying the feedback effects that additional brown fat might have on the thyroid. Hypothetically, the thyroid doesn't just signal brown fat -- brown fat could also be signaling back to the thyroid. That is, because the thyroid stimulates under active brown fat activity, couldn't brown fat also stimulate an under active thyroid?

Lapa et al. (2015) reported findings related to that question in the Annals of Medicine. Evaluating thyroid cancer patients after total thyroidectomy, their study determined that patients with active brown fat tissue had significantly higher levels of thyroid-stimulating hormone in their bloodstreams than a control group without active brown fat. In other words, even after total removal of the thyroid gland, those patients with active brown fat were still producing hormonal signals intended to stimulate thyroid activity.

But of the 126 patients in their study only 6 were found to have active brown fat.

The only way to recruit and maintain brown fat is regular cold exposure, and it's likely that cold plunge practices were critical to Hashimoto's reversals that Dr. Hunt experienced.

What this suggests is that hypothyroidism, like obesity, type 2 diabetes, and a host of other ailments may be just a suite of maladies exclusive to western, educated, industrialized, rich, and democratic (WEIRD, Henrich et al. 2010) countries characterized by technological comfort, ultra-processed diets, and a lack of cold exposure.


About the Author

Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.

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Martin Siebert
Martin Siebert
Dec 20, 2022

Adrienne Jezick, today I quantified some values to understand/observe my cold shower after WHM breath and I took measurements temps (armpits) after icy shower, for 8...10°C (water). Indoors 18...20°C (Summer time), with 4 min cold shower I did 12 min horse stence= 32.7°C. (I'm scaried with 32°C).

With Tingling in the legs and a weird cold feelings, but not shivering. I did more 5min H.S. after measurement. I did some stretching Ex...and I take little hot coffee. Every 30 minutes...I measured: 34.1°C...34.7°C...and at the end with 35.5°C I'm normal (low thyroid).

Physicians here only give medicine and ask to stay away from the cold.How far am I going right or overdoing it? I already practice WHM for more than 5…


Since we wrote this article, a group of scientists from Singapore published a study in the prestigious journal Scientific Reports that investigates the possibility that activation of brown fat will signal the thyorid..

What did they find?

Two hours of mild cold exposure (~14.5 °C, about 58 °F using a cold vest) resulted in reliable increases in thyroid hormones (Sun et al. 2020) that enhance metabolic energy expenditure and thermogenesis.

The findings, which they claim "have never been previously been reported anywhere thus far in the extant literature," support "the hypothesis that the positive feedback loop bridging between the thyroid gland and brown fat is not trivial, but reveals an intriguing aspect of homeostatic regulation that probably plays a definite role…


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