How Does Keto Affect Hypothyroidism?

How Does Keto Affect Hypothyroidism?
By: Eric Cameron, APRN, FNP-C

This week's Medical Monday will be discussing the relationship between the utilization of the ketogenic diet and thyroid function.  Specifically, we will look at the claim that the ketogenic diet, when utilized long-term, will result in hypothyroidism.  For those who have looked at the research surrounding this claim, you will likely already know that the data cited for this claim is strictly associative and shows no causative relationship.  That being the case, we will try to unpack this data and determine if there is any merit to the claim or whether the data has simply been misunderstood.  Forewarning, Endocrinology is a rather complicated subject with a vast number of external and internal influencing factors.  All of these factors make it exceptionally difficult to pinpoint exact causes for changes in endocrinological function and can all be considered "confounding variables" when discussing research surrounding the endocrine system.  With that said, we will do our based to account for these issues during this discussion. 


Before we start dissecting the data surrounding this claim, let's begin by discussing what hypothyroidism is and how the diagnosis is made from the perspective of the clinician.  Hypothyroidism is the dysfunction of the thyroid most commonly characterized by an elevated TSH (thyroid stimulating hormone), low T3, and sometimes low T4.  These two hormones are the active thyroid hormone components with T3 coming from T4.  The TSH levels become elevated when the pituitary glands is triggered by a negative feedback loop system.  This is typically triggered when the actual active thyroid hormone (T3) is too low.  When this happens, the pituitary gland tells the thyroid to create more T4 by releasing TSH.  For those who don't work in medicine, that means that the pituitary gland itself is actually making the TSH, not the thyroid.  Once secreted, the thyroid should respond by creating more T4 which should eventually be turned into the active thyroid hormone T3.  There are a number of factors that can influence this pathway but we will primarily focus on dietary influence. 

While explaining this diagnosis and how it is made, it is important to talk about another syndrome known as sub-clinical hypothyroidism.  This diagnosis is essentially the same; however, patients may have hormone levels that technically fall within the range of "normal" but may be on the very low end of this.  With that being the case, these individuals may still be quite symptomatic and suffering the same symptoms that someone with a clear case of hypothyroidism may suffer.  There is actually a fair amount of evidence that these individuals also benefit from thyroid hormone supplementation, but this is a discussion that should take place between the healthcare provider and the patient rather that just putting the patient on this supplementation straight off.  Other sources for their symptoms may also need to be excluded first. 

So what kind of symptoms do individuals typically have when suffer from hypothyroidism or sub-clinical hypothyroidism?  The most common symptoms often include a generalized slowing of metabolic processes which can lead to fatigue, slow movement, slow speech, cold intolerance, constipation, weight gain, delayed relaxation of deep tendon reflexes, and bradycardia (slow heart rates).  It can also result in the accumulation of matrix glycosaminoglycans in the interstitial spaces of many tissues in the body (sorry for the overly sciency vocabulary here).  This can lead to course hair and skin, puffy face, enlarged tongue, and a horse voice.  These symptoms are more easily recognized in younger individuals as they are less likely to be confuse with age related changes.  

Some other common symptoms you can expect to see include the following:

Skin - cool and pale due to decreased blood flow.  Thinning of the skin as well as hyperkeratosis leading to dry rough skin.  Sweating may be decrease, hair may become more course and brittle, and nails often become more brittle.  Some patient also experience non-pitting edema (known as myxedema) and may suffer from hypopigmentation in the skin known as vitiligo.  In more severe cases, alopecia is seen which is the loss of hair. 

Eyes - some patients experience edema (swelling) around the eyes, though this is more commonly seen after he treatment of Grave's disease. 

Hematologic (blood) - different forms of anemia have been seen in patients suffering from hypothyroidism with 10% suffering from pernicious anemia secondary to chronic autoimmune thyroiditis. This may require medical intervention which will be dictated by the type and severity of anemia. 

Cardiovascular - decreased cardiac output mediated by reduction and heart rate and contractility. This may contribute to reduced exercise capacity and shortness of breath during exercise. Those with existing heart failure and angina may also experience a worsening of these symptoms when hypothyroidism develops or is not well controlled.  Patients may also be at an increased risk for pericardial effusion, hypertension, hypercholesterolemia, and hyperhomocysteinemia which plays a role in certain types of anemia.

Respiratory - fatigue, shortness of breath, rhinitis (runny nose), and decreased exercise capacity have been observed in a number of patients with hypothyroidism thought to be related to respiratory weakness and reduced pulmonary response to hypoxia (lack of oxygen) and hypercapnia (too much CO2).  Sleep apnea also occurs in some patients with hypothyroidism. 

Gastric disorders - constipation is the most common symptom for GI but patients may also experienced decreased taste sensation, anemias due to decreased absorption in the gut, increased risk fo celiac disease, nonalcoholic fatty liver disease, and weight gain. 

Reproductive abnormalities - women can experience irregular menses, lack of menses, or frequent and severe menses and may experience issues with fertility. Men also may experience low levels of testosterone leading to decreased fertility, hypogonadism, decreased libido, decreased energy levels, weight gain, and other issues that coincide with low testosterone levels in men. 

Neurological dysfunction - this can result in movement disorders such as Parkinson's disease, peripheral neuropathies such as carpel tunnel syndrome and polyneuropathy, and increases risk for other issues such as vision loss, hearing loss, Myasthenia Gravis, and chronic headaches.  Some research supports that hypothyroidism may also play a role in the development of Alzheimer's disease.  These are only a few of the neurological issues associate with hypothyroidism. 

Musculoskeletal - weakness, cramping, and myalgia (muscle pains) are common.  From an objective standpoint, patients have also been observed to have elevated serum creatine kinase (CK) and have made complain of joint aches/pains/stiffness that seem to correlate well with elevated CK and elevated TSH levels. 

Metabolic abnormalities - Hyponatremia (low sodium), elevated creatinine (poor renal function), poor lipid clearance resulting in elevated cholesterol levels, and weight gain have been observed often in hypothyroid patients. 

Drug clearance - patients may have a decrease clearance of certain drugs including anti epileptic (anti seizure) drugs, hypnotics, anticoagulants (blood thinners), and opioids. 

Well that is a lot of possible side effects from one little organ!  But with all of that in mind, what role does the ketogenic diet play???  If people claim that the ketogenic diet causes hypothyroidism, why the heck would we risk developing all of these issues?  The answer is simple... because the ketogenic diet has NOT been shown to cause hypothyroidism and has also not been shown to decrease control over hypothyroidism.  So where do these claims come from?  Most likely from a misunderstanding or misrepresentation of the data in the research looking at this topic.  

The common finding that leads to researchers believing the ketogenic diet and other low-carb diets result in hypothyroidism is the fact that a small number of patients have been observed to have a decrease in serum concentrations of T3 after starting the ketogenic diet.  While this is part of the clinical diagnosis, it is not the whole thing.  These patients are also reported to be asymptomatic (meaning without symptoms of hypothyroidism), typically have normal TSH and T4 levels, and have a normal metabolism.  Their metabolic rates (one of the key characteristics of hypothyroidism) is NOT depressed when in ketosis.  In fact, research has shown the exact opposite.  Because of this, researchers within the ketogenic community believe that this response is very similar to the insulin response we see in our diabetic patients who have become keto-adapted.  While the levels of insulin may be decreased (which is a good thing), their response to the action of insulin is increased resulting in a reversal of their insulin resistance.  If the same holds true for thyroid hormone, it would make perfect sense as to why the TSH is normal despite the T3 being mildly depressed.  If you become more sensitive to the action of T3, the body will not initiate the negative feedback loop telling the pituitary gland to secrete more TSH and encourage secretion of T4 to become T3.  

This exact hypothesis has actually been discussed by ketogenic researches Jeff Volek - pHD, and Steven Phinney - pHD, MD, through their blog platform on Virta Health.  They have both researched this topic during their research on the utilization of the ketogenic diet and have spoken quite favorably on the use of this diet in patients with and without pre-existing hypothyroidism.  Again, in the limited research that tries to suggest this being an issue, many of the participants are not actually ketogenic and, for those that are, they are not observed to be symptomatic with these subtle changes in their T3 levels while in ketosis. 

To further the argument against keto resulting in hypothyroidism, there is only ONE study that claims there is a causative type association between the diet and thyroid function.  In this study, 120 drug-resistant epileptic patients (children) followed a ketogenic diet for 1 year.  Of those 120 children, 16.7% were diagnosed with hypothyroidism and placed on a thyroid supplementing drug.  They based their conclusion of keto causing hypothroidism on this data an failed to include the thyrotoxic effect of previously administered anti-epileptic medications which were the most likely culprits for these children developing hypothyroidism.  They even noted that some of the children on the ketogenic diet had normalized thyroid function on the diet which was previously abnormal due to anti-epileptic medication induced thyroid impairment. Hmm... sounds like a significant finding to just gloss over.  The other study that is commonly sited looks at a "risk relationship" and only evaluated 28 children with epilepsy on a ketgenic diet for nearly 2 years and a change in T4 and TSH levels were observed.  However, no functional changes were observed and patients remained asymptomatic despite this finding.  They categorized this as a "risk factor" for developing hypothyroidism. 

So what does this all mean for the individual with hypothyroidism looking to do keto?  And what does it mean for those who do not have hypothyroidism but may have first-degree relatives with this disorder or who are just worried about developing hypothyroidism.  Well, there is no more information to support that keto causes hypothyroidism than general calorie restriction.  In fact, if the above mentioned theory proves to be true, it may actually improve hypothyroidism.  So what it means is that you need to watch for clinical signs of hypothyroidism, work closely with your healthcare provider to manage your medications, and stay strict in maintaining this way of life.  All things you should be working to do anyways.  The ketogenic lifestyle has so many incredible benefits beyond weight loss and may truly improve your quality of life.  Don't let a couple of poorly interpreted/relayed studies scare you away from those benefits.  Talk to your healthcare provider and see if this may be the right approach for you! 

So thats all on how the ketogenic diet and hypothyroidism relate to one another.  I hope you've found this subject insightful and I hope it helps the next time you go to discuss this issue with a friend, colleague, or your healthcare provider.  

If there are any other topics you'd like me to discuss surrounding the ketogenic lifestyle and health, please feel free to shoot me a message on my Instagram or follow me on Facebook under and message me there! 

Remember, this blog does not constitute medical advice and I am not your medical provider.  So when making any dietary changes, include your healthcare provider so it can be does safely and sustainably!

Kassey CameronComment