The Effect of a Ketogenic Diet on Thyroid Hormone

ThyroidDuring my most recent cholesterol blood work, I also checked my thyroid hormone levels in an effort to figure out why my cholesterol has gotten so high while I’ve been in nutritional ketosis.

One of the possible explanations was that:

Chronic low carb -> Hypothyroidism (low T3) -> Decreased expression of LDL receptors in the liver -> Higher serum cholesterol

Background – Here is an oversimplified explanation of thyroid physiology

  • Thyroid Stimulating Hormone (TSH) – This is the hormone your brain sends out telling your thyroid gland to produce more thyroid hormone.  If there is too little thyroid hormone, your brain will send out more TSH, and if there is too much thyroid hormone, it will release less TSH.
  • Free T4 – This is the form of thyroid hormone sent out by the thyroid gland to regulate metabolism in the rest of the body.
  • Free T3 – A more potent form of thyroid hormone.  Tissues that receive T4 will convert it to T3 which is about 4x more potent than T4.  The reason T4 is sent out instead of T3 by the thyroid gland is because T3 only has a half life of 2.5 days where has T4 has a half life of 6.5 days.  One of the effects of T3 is:  stimulates the breakdown of cholesterol and increases the number of LDL receptors, thereby increasing the rate of lipolysis.
  • Reverse T3 (rT3) – Tissues that receive T4 can also convert it to rT3, an inactive form of T3.  This occurs in certain conditions in which your body tries to conserve energy by slowing down metabolism such as fasting, low carbohydrate intake, physical or emotional stress, illnesses, surgery etc.  Thus, under these conditions, not only will you have less overall T3 floating around, but rT3 can block T3 receptors so that the T3 you have left are even less effective.

Results From 3/11/13

  • TSH: 4.350 uIU/mL (0.450 – 4.500) — 1.33 (11/16/12) 
  • Free T4: 1.09 ng/dL (0.82 – 1.77)
  • Free T3: 2.1 pg/mL (2.0 – 4.4)
  • rT3: 18.5 ng/dL (9.2 – 24.1)

A cursory glance shows that all my numbers are within the normal range meaning that my thyroid function is normal, but on closer examination, you see that my TSH is at the very upper limit of the normal range, and both my Free T4 and Free T3 are on the lower limit of the normal range (especially Free T3).

I also came across this insightful article by Dr. Sara Gottfried, supported by this report, stating that the revised normal range for TSH is 0.3 – 3.0 mIU/L.  Using this new reference range, I would be considered hypothyroid. There’s also data out there showing that there really isn’t exactly a normal range for rT3, and that the most accurate way to interpret rT3 levels is as a ratio relative to how much Free T3 is available.

Since labs give results in all types of units, the folks at put together a handy dandy calculator that takes all that into account for you, where all you need to do is input your numbers and select the values, and it will automatically calculate your Free T3/rT3 ratio.  A normal ratio, should be greater than 20.

My Free T3/rT3 ratio is 10.8.

What does all this mean?

Even though I didn’t have a full thyroid panel done in 11/2012, my TSH was 1.33, which  is in the normal range under both the previous and new guidelines.

After three months of nutritional ketosis my TSH, free T3, and free T4 indicate that I’m hypothyroid, or at the very least subclinically hypothyroid (depending on which reference range is used).  This is also supported by my low Free T3/rT3 ratio.

Over the course of this n=1 experiment I haven’t really noticed any symptoms of hypothyroidism:

  • Fatigue – Only when I didn’t get enough sleep.
  • Increased sensitivity to cold – Nope.
  • Constipation – Nope.
  • Dry skin – No dryer than normal.
  • Unexplained weight gain – Maybe?  This may explain my stalls in weightloss
  • Puffy face – Nope.
  • Hoarseness – Nope.
  • Muscle weakness – Nope.
  • Elevated blood cholesterol level – YES!!!!
  • Muscle aches, tenderness and stiffness – Only after Crossfit and intense BJJ sessions.
  • Pain, stiffness or swelling in your joints – Only when I don’t tap out in time during BJJ!
  • Heavier than normal or irregular menstrual periods – I don’t have the parts to do this…
  • Thinning hair – Not really, but I generally keep my hair short, so it would be hard to tell.
  • Slowed heart rate – Resting heart rate is in the 50’s-60s.
  • Depression – Nope.
  • Impaired memory – Nope.

The entire reason I tested my thyroid levels was to explore possible explanations as to why my cholesterol is so high, and these results make me think that it truly has to do with my thyroid levels.

What is probably going on is the very low level of carbs I’m eating while being in nutritional ketosis is turning off my body’s production and utilization of thyroid hormone in order to preserve energy, and my high cholesterol is just a side effect of this.

Here’s a good article discussing this phenomenon. This also probably explains why my weight loss hasn’t really gone anywhere, since being hypothyroid slows down my metabolism making it harder to lose weight. Stay tuned for part 2 to see how I try to address these issues.


27 Responses to The Effect of a Ketogenic Diet on Thyroid Hormone

  1. Nadia Peters says:

    Very interesting… My cholesterol levels also soared ever since I started very low carb. I do not have a weight issue, and had ‘normal’ LDL, HDL and TG’s before going Low Carb. I started it because, having been Low Fat High Carb for over 25 yrs, I started showing symptoms of metabollic syndrome (despite no weight problem, on the contrary, rather underweight), i.e. low energy, fatigue especially after meals. My energy levels are fantastic on low carb, and I feel really good. Except for the skyrocketing of my LDL cholesterol …. as well as … leg muscle cramps at night, and very tender knee joints….I will have my thyroid checked after reading your post!

  2. Dale Seng says:

    Nadia Peters, You may wish to consider magnesium supplementation for the cramps. Volek and Phinney recommend Slow-Mag, Mag-64 or Mag-Delay for 20 days. Your cramps should go away in 14 days, but keep taking it for 20.

  3. Jim Jozwiak says:

    I had to get carbs lower than I expected in order to make the ketogenic diet work right.
    21 grams on non-fiber carbohydrate works the best for me.
    I had to use nutrition software to find exactly where the right number was.

    • BJJ Caveman says:

      Did you notice any difference with the amount of protein you consumed? Some people report that protein makes an even bigger difference for them!

  4. […] with nutritional ketosis regarding my cholesterol (Part 1, Part 2, Part 3), thyroid hormone (Part 1), and skin rash, I decided to take a break from nutritional ketosis to see what would […]

  5. Richard says:

    Very interesting. I wonder if a weekly carb refeed would serve to give the thyroid a kick back into action?

    • BJJ Caveman says:

      That is the thought behind Tim Ferriss weekly cheat days on the Slow Carb Diet.

      It’s definitely something to look into. A lot of body builders who eat ketogenic diets utilize weekly re-feeds precisely for this reason. It lets the body know that there is enough energy around and that it doesn’t need to shut down thyroid hormone production to slow down the metabolism to go into ‘energy conservation mode.’

  6. […] down since we have less glycogen, other hormones are affected such as our thyroid hormone levels (Parts 1, 2), and our cholesterol can either stay the same, go down, or go way up (Parts 1, 2, 3, 4), among […]

  7. kevin says:

    Ok I know your not a doctor but I used to have hyperthyroidism now Im probably hypo so doing the Keto diet might not be a good idea? My last lab to many years ago My cholesterol was high but my TSH REFLEX FT4 was
    Component Standard Range Your Value Flag
    TSH 0.4 – 4.7 mcIU/mL 3.5 I would say im a good 30lbs heavier since then I work out 3-5 times a week, protein shakes I will say maybe too much fruit? Im going to have a full panel done soon

    • BJJ Caveman says:

      I would probably wait until your next thyroid panel before proceeding. If you are hypothyroid or even borderline hypothyroid, I’d just be more vigilant while attempting a ketogenic diet. Here are a few things I would do:

      1. Pay close attention to how you feel… if you are more sensitive to cold, more fatigued etc.
      2. Supplement with Potassium Iodide
      3. Do followup labs in a month or so to make sure thyroid numbers aren’t getting worse.
      4. Consider periodically carb re-feeds. While this will push you out of ketosis, if you are fully ketoadapted, it shouldn’t take more than a few days to get back in.

      Hope this helps.

  8. […] can read about my thoughts on my prior thyroid numbers here: Part 1, Part […]

  9. […] the course of my experiment I developed a bout of hypothyroidism which is apparently common in the very low carb community, and is the body’s way of […]

  10. […] The Effect of a Ketogenic Diet on Thyroid Hormone (3,029) […]

  11. […] The Effect of a Ketogenic Diet on Thyroid Hormone (3,687) […]

  12. […] The Effect of a Ketogenic Diet on Thyroid Hormone […]

  13. […] The Effect of a Ketogenic Diet on Thyroid Hormone […]

  14. […] is a brief summary I wrote in the early life of this blog regarding thyroid […]

  15. gary l says:

    Those who live in ketosis may perhaps simulate a paleo lifestyle. Virtually all thyroid data is from averages of individuals who live on a grain-loaded and sugar-coated diet which does not resemble the conditions we humans evolved under. If our society in general had a more healthy diet based on protein and saturated fats then the average thyroid numbers probably would shift considerably towards the values you exhibit. Perhaps the problem is not with your thyroid values, but rather with the thyroids in a general population with elevated blood sugar, insulin resistance and obesity which leads to overproduction of thyroid hormones thus falsely altering the overall average hormone values.

    • BJJ Caveman says:

      This is a great point, and is also part of my thinking as to my wacky cholesterol numbers.

      It’s interesting to see though that adding just 1 day of carbs back in for the week (with cyclic keto) pretty much normalizes the values (with the exception of RT3).

  16. Cheryl says:

    well, I just got my lab report and stumbled upon your info and glad I did! As my doctor is freaking out and is in the process of sending me off to a specialist as my thyroid level is TSH level is a whopping 58.3! normal range on report says it should be between .27-4.2! My cholesterol reading is through the roof. I’ve been on it since beginning of march and my carb intake was no more than 30g a day.

  17. Jim says:

    Great insight Caveman.

  18. Bruce Sands says:

    Hi When I was in deep ketosis my triglycerides shot up to 500 and my cholesterol went over 300. I got rid of saturated fat, and stayed in ketosis with mono and poly fat, and my triglycerides went down to 70 and my cholesterol to 170. There is apparently some research that shows about 1/4 to 1/3 of people doing low carb can’t do saturated fat. There is some information on this at the Lecturpad website, Dr Thomas Dayspring has done a lot of writing about LC diets, and has noticed this.

  19. […] in controlling my thyroid disease, which otherwise would likely get worse on my LCHF. Here is an explanation on the connection between T3 levels and low […]

  20. […] The Effect of a Ketogenic Diet on Thyroid Hormone […]

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