Thyroid Hormones (FT4, FT3): What's Optimal? 

very interesting, as always. The thyroid system appears to me as one of the most complex in the body. While the textbook descriptions are kind of simplified, I think there is a whole bunch of regulations not yet described. For instance, immune system and energy producing system are cross linked in multiple ways, hence i would expect that certain activities in the immune system also affect the thyroid system.... what do you think? About Selenium: there is also a lot in sardines, according to cronometer, which is my main source of it .( the units for the T3 conversion are likely be the other way round)

Really interesting video - and thanks for shedding some light into the thyroid hormone system. Seeing the importance of this fT3/fT4 ratio, I wonder even more why doctors typically only prescribe levothyroxin, which is equivalent to fT4. This means your body needs to convert quite a lot of fT4. There are alternatives which give the body also some fT3, and are better tolerated by some people (e.g., natural Desiccated thyroid from cows or pigs) In any case, curious to see how Selenium will influence this. I think you are aware that Brazil nuts have a relatively high natural radiation within them (for kids and during pregnancy not recommended) - I would assume even in your dose you should be ok

I really appreciate your work and I'd like to say we're in the same boat. I started doing the same last semester I've been eating Brazil nuts for the past 22 years now, always 3 to 4 nuts a day until 2 years ago when I cut it down to just 1. I strongly suggest you buy them shelled and keep them in the freezer and at least 8 hours before consuming them, crack 2 or 3 open, put them into a glass of water and squeeze a few drops of ACV, lemon or lime to kill any possibly existing fungus as well as to draw phytic acid, which is a nutrient robber. Wash them off with filtered water right before eating them and with them take 15mg of chelated zinc.

CR almost certainly is contributing to the April 2024 test. There's pretty extensive literature on weight loss subjects that shows the ratio reduces. Most of those studies are around a ~10% reduction, which wouldn't explain a 40% decrease in your case.

Excellent review. I am an active middle age guy. My ft3/ft4 got as low as 0.19 (active mid 40's) before I started liothyronine. PCP and I first tried levothyroxine with no effect on FT3 and a worsening of RT3. Now slowly titrating FT3. Working on getting it more optimized. Interested to see what you dig up on Uric Acid something else I am working on optimizing.

I forgot to say I also took lugol from 2015 to last week when I decided to go off iodine to see how it reacts. While It may sound counterintuitive, it's a reasonable course of action to lower your anti TPO's, which in my case went from 28 to 41 in just 4 months.

Sharing some info I got from Concensus AI: (I have not fully verified, nor formated, just a quick copy and paste) Selenium: Selenium deficiency is associated with a higher FT4/FT3 ratio, indicating impaired conversion of T4 to T3. Supplementation of selenium can normalize this ratio by increasing FT3 levels and decreasing FT4 levels. [2][3] Zinc: Higher serum zinc levels are positively associated with the FT3/FT4 ratio, suggesting that adequate zinc levels support the conversion of T4 to T3. [2] Dietary Intake: Frequent consumption of foods with a high glycemic index is positively associated with both FT3 and FT4 levels, while foods rich in saturated fatty acids and high protein concentration show a negative association with these thyroid hormones. [1] Nutrient intake, particularly in the context of obesity, can influence thyroid hormone levels, with decreased nutrient intake being linked to lower FT3 levels. [4] Omega-3 Fatty Acids (EPA): EPA (eicosapentaenoic acid) is positively related to the FT3/FT4 ratio, indicating that omega-3 fatty acids may enhance the conversion of T4 to T3. [6] Creatinine: In hemodialysis patients, a higher serum creatinine level, which is a marker of muscle mass, is positively correlated with the FT3/FT4 ratio. This suggests that muscle mass may play a role in the local conversion of T4 to T3. [7] 1 - "The effect of food groups and nutrients on thyroid hormone levels in healthy individuals.","Frequent consumption of high glycemic index foods positively affects thyroid hormone levels, while foods rich in saturated fatty acids and high protein concentration negatively affect thyroid hormone levels.","Dubravka Brdar, I. Gunjača, Nikolina Pleić, V. Torlak, Petra Knežević, A. Punda, O. Polašek, C. Hayward, T. Zemunik",2021 2 - "Blood micronutrient and thyroid hormone concentrations in the oldest-old.","In extreme aging, blood levels of specific micronutrients are associated with serum iodothyronine levels, while younger subjects show no significant association.","G. Ravaglia, P. Forti, F. Maioli, B. Nesi, L. Pratelli, L. Savarino, D. Cucinotta, G. Cavalli",2000,94,"Several micronutrients are involved in thyroid hormone metabolism, but it is unclear whether their marginal deficits may contribute to the alterations in thyroid function observed in extreme aging. The relationships among blood concentrations of thyroid hormones and selenium, zinc, retinol, and alpha-tocopherol were studied in 44 healthy Northern Italian oldest-old subjects (age range, 90-107 yr), 3 - Thyroid function in patients with selenium deficiency exhibits high free T4 to T3 ratio","Patients with selenium deficiency may have abnormal thyroid hormone levels, including high free T4 and FT4/FT3 ratio, which can be improved by supplementation.","Ryohei Kobayashi, M. Hasegawa, C. Kawaguchi, N. Ishikawa, K. Tomiwa, M. Shima, K. Nogami",2021 4 - Serum concentrations of total T4, T3, reverse T3 and free T4, T3 in moderately obese patients.","Obesity is linked to a decrease in serum total and free T3 concentrations, with nutrient intake being the most significant factor responsible for this decrease.","P. Chomard, G. Vernhès, N. Autissier, G. Debry",1985 5 - FT3/FT4 ratio is correlated with all-cause mortality, cardiovascular mortality, and cardiovascular disease risk: NHANES 2007-2012","Higher FT3/FT4 ratio is associated with decreased all-cause mortality, cardiovascular mortality, and CVD risk, while higher FT4 and FT3/FT4 ratio are associated with increased cardiovascular mortality and CVD risk.","Xueyan Lang, Yilan Li, Dandan Zhang, Yuheng Zhang, Nilian Wu, Yao Zhang",2022, 6 - Relationship between thyroid hormone parameters and exposure to a mixture of organochlorine pesticides, mercury and nutrients in the cord blood of newborns.","Prenatal exposure to p,p'-DDE, HCB, and EPA in a mixture may affect newborn thyroid function in independent and interactive ways, but the overall effects of the mixture on thyroid hormone parameters were not significant.","Ju Wang, Lu-Lu Cao, Zhen-yan Gao, Hong Zhang, Junxia Liu, Susu Wang, Hui Pan, Chong-huai Yan",2021 7 - "Association of Reduced Free T3 to Free T4 Ratio with Lower Serum Creatinine in Japanese Hemodialysis Patients","Lower muscle mass may contribute to the development of low T3 syndrome in hemodialysis patients, as it is independently and positively associated with the serum FT3/FT4 ratio.","M. Inaba, K. Mori, Y. Tsujimoto, S. Yamada, Y. Yamazaki, M. Emoto, T. Shoji",2021 8 - "High free triiodothyronine and free-triiodothyronine-to-free-thyroxine ratio levels are associated with metabolic syndrome in a euthyroid population.","Elevated levels of FT3 and FT3/FT4 ratio are associated with metabolic syndrome in a euthyroid population.","Diego Urrunaga-Pastor, Mirella Guarnizo-Poma, Enrique Moncada-Mapelli, Luis G Aguirre, Herbert Lázaro-Alcántara, Socorro Paico-Palacios, Betzi Pantoja-Torres, Vicente A Benites-Zapata",2017,

Should the ratio be between pmol to pmol? Btw, I'm hypothyroid too, dose 107mcg per day. Ft3 will increase with caloric intake. Weight loss crushes ft3. Mine fell from 3.5 pg/ml to 2.8 during weight loss. This might recover when I start eating more to maintain. It is clear why T3 falls during weight loss. Metabolism slows down to fight the weight loss. T3 is directly responsible for the metabolic adaptation in BMR and NEAT reduction seen during weight loss. T3 also falls much more on a low carb/keto diet when the body thinks it's starving even compared to isocaloric but higher carb diet. Finally, T3 is also low for ICU patients going to die soon. It's a marker of poor health. It's called non thyroidal illness syndrome.

Gotta love ya, Mike. You've been down in the science data shaft now for nine years wearing your miner's hat--with your coal spade and a canary sifting through the detritus for longevity gems to share with your herd. I wonder how tedious your method gets for you when it comes to weighing all your food and subjecting yourself to strict eating windows and boxing contender weight-lifting regimens. What do you do for fun? Teaching your paid clients your longevity method must be a tough sell if they try to do what you do. As a Health Coach, I find it hard to get people to make any kind of profound change to their diets. And ask them to incorporate exercise? It's why I haven't started charging yet. Getting people to make healthy changes only works for those who are all in and seriously want to improve. As a fellow home vegetable grower, I would like to recommend two super nutritious veggies I reluctantly tried to see if they'd flourish indoors. I bought 4 ounces of radicchio and Chinese celery seeds from True Leaf, and wow, these two nutrient-dense beauties have taken off in a big way. You should check out the Chinese celery and radicchio nutrition profile. You told me that you do not have longevity in your DNA. But just doing what you are doing should give you added healthy years, I'd think. On a different note, though, I'd like to share with you one of my favorite quips from Bernardo Kastrup: "The more transcendent you become, the less you will care about surviving." As a fellow philosopher, you may have come across his work. I will share with you a recent video that I find riveting. It deals with the science of consciousness and the theory that there is a much deeper meaning to life-or what we currently perceive 'life' to be. This interview video discusses thoughts and theories from Bernardo Kastrup and Christof Koch. These may be two of the smartest dudes on the planet. I guess I should warn you that the subject matter involves both of them speaking about their journeys under the influence of psychedelics. I am trying to find a reliable source for experimenting with psychedelics but have found only street trash from questionable characters. A website I have found, Psychedelic Passage, could be the pathway. Bernardo Kastrup VS Christof Koch ://ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-qzwC7sXyhWQ.htmlsi=_9BZPdutUsHQD9e This video-should you choose to watch it-is 1:40 long and gets more interesting as it goes on. It's better if you watch it in one sitting, but it's not necessary. At this point, I think living long enough to become transcendent is all we can hope for. We learn and grow so much every year of our lives. Spoiler alert! Bernardo and Christof say this place we inhabit now is NOT reality. This idea, coming from these two brilliant men, is a chilling one to ponder. This life may just be step one of a much deeper and interesting plain of existence. Please watch the video when you have time. Thanks

Hello Dr. Lustgarten. May I suggest that you make a video on body temperature as an ageing/longevity biomarker and how to lower/optimize it?

Love the short often vids

Great video (as usual) What do you think about supplementing with Tyrosine ?

Nothing about TSH? I only have a few data points for FT3 and FT4 as well. Getting those tested is kind of expensive and tricky to order, especially the Reverse T3. So few people measure these. I was hoping to see more on how TSH relates to FT3 and FT4. I've actually been able to go down from 100mcg L-thyroxine to 88mcg, though I have taken 100mcg for over 20 years. Running does seem to impact TSH levels for me. I look forward to more videos on this.

I have measured my TSH/FT3/FT4/rT3 several times in past few years .. Also Se, Zn, Fe, I etc. All in good shape. 1) T4---> T3 conversion requires Carbs or else Adrenal activation blocks/reduces conversion for protection. Most Keto/Carnivores have low fT3 for this reason. 2) Veggies have in general higher fT3. Fruits+ Vegs keeps thyroid happy 3) CR will reduce fT3 ( increase in rT3) as body goes in starvation mode- Anything that makes body think scarcity of food will dial down fT3. 4) Stress shoots rT3 to deal with stress and lower fT3. 5) Besides iodine, good Se, Zn and Fe panel needed for thyroid to function smoothly and conversion. 6) Anything that activates adrenal ( epinephrine, cortisol, etc.) will dial down fT3 for protection - HPA and HPT axis work in coordination besides HPG axis ( Hypothalamus - Pituitary- Adrenal or Thyroid or Gonad) Sum total- Most happy people who eat lots of veggies ( fruits + Veggies) have good thyroid besides heart/brain.

Amazing video man, thanks as always. I really dislike Brazil nuts, would you recommend any other food that is high in selenium? Failing that, I know you don’t like the supplement route as much, but what would a safe low-medium dose be to top up my intake from whole foods? Appreciate you!

very good thanks

growth hormone also falls with age . it is a age clock equvalent. so statistically , those with low growth hormone being of older biological age will have higher mortality. but genetically lower growth hormone give u longer life. I suspect thyroid hormone fall under this category

i bought a 'natural' thyroid supplement in torontos chinatown many years ago for $30 , bottle had 400 small pressed pills turned out to be dried pork thyroid or something to that effect which had my ft3, ft4 was through the roof and tsh was

Have you ever ordered lab analysis of any food item to see whether the content of compounds of interest match the numbers from literature? Seems somewhat important to know in this case, since there's an upper limit you're already close to. That is if the data is applicable.

Hi, have you ever test the antibodies to see if your hypothyroidism is an autoimmune problem? (like Hashimoto) and how do you have find your best dose of Levothyroxine? thank you

I have by far the lowest level. According to that, Im 120yo. Ratio is even more worse: 0.22 Ft4: 17.12pmol/l Ft3: 4.9pmol/l Im 44yo. Now Im really shocked. Ive also had some tests in the past: they were a bit better, but fae away from optimal. At least one bloodmarker there I am over 20. Haha. -.-

Why not use dessicated thyroid or levothroxine plus t3 . As you take more levothyroxine , you produce more t3 AND rT3. RT3 competitively attaches to receptors and block t3 actions? Selenium may help but doesnt solve the rT3 . Check rT3 too!

Very helpful. Thanks. Couldn’t you just increase Levo thyroid hormone to increase the ratio?

AC on... feeling the summer?

Hi! Thanks for the video! I'm diagnosed with hypothroidism and so take 150 mg levotyroxine every day. My FT4 is 20.7 pmol/L and FT3 5.2 pmol/L. Does this mean that my FT3/FT4 ratio is 0.25, which is the high risk ratio? If so I will try out the idea of "supplementing" with brazil nut to raisen selenium!

I've read research showing that the selenium content of brazil nuts varies hugely, depending on source, growing conditions etc. Sorry I don't have the reference to hand. So, you could be massively exceeding or undershooting your 400mcg target, even from batch to batch of brazil nuts from the same shop. In this case, you might be better off initially taking a supplement to properly control your selenium intake, at least as a proof of concept.

I am surprised you would elevate selenium after you made a video that showed optimal intake to be 150-200 micrograms or something like that, and higher levels in your data appeared to hurt several biomarkers. Well, there is nothing wrong with testing, rather than just trusting the correlations. I wish there were more people out there generating and presenting good data like this.

In reviewing this video again, I'm trying to understand the ratio: FT3/FT4. If FT3 is 2.9 and FT4 is 0.99, shouldn't FT3 be in the numerator? Even if it's the other way around, wouldn't your first ratio be 0.34 instead of 0.30? My latest thyroid check I got the exact same results as you did on 4/29/24. My Reverse T3 was 21. My doctor said my T3 was suboptimal and that reverse T3 was "high normal." I'm taking 88mcg levothyroxine, but my doctor just now switched me to the brand Synthroid, saying that it helps improve conversion. I'm interested to know if you have tried using the brand. I've never seen anyone calculate this FT3/FT4 ratio, so it's nice to have and additional metric to track. And I look forward to your follow-up on this after your next test. It's unfortunate that these test are relatively expensive, and I have not even found a way to order reverse T3 directly from Quest.

I have a high ratio of 0.487 with T3 5.57 pmol/l and T4 11.43 pmol/l. I'm 37 and so it seems my T4 is super low and T3 is super high based on this pictures. My lab tells me my reference range is 3.53 - 6.80 for T3 and 7.70-14.20 for T4. I'm having trouble to make sense of this data.

Why selenium/brazil nuts and not cytomel/liothyronine to increase the T3 to T4 ratio?

conquer ageing- may i ask, so how many brazil nuts per day does that translate to? 2-4? i only eat around 2 brazil nuts per day, there is such a thing as selenium toxicity, most literature/vids say only eat no more than 2 per day. interesting topic, i have to take 150mcgs tirosint liquid levothyroxine, can't convert pill form. please let me know the brazil nut amount. thanks.

Hi, is your Hypothyroidism an Hashimoto's disease?

You should supplement with Lugols iodine.

Sir i am watching your videos out of order. I recall your SHBG is very high. There is some correlation between thyroxine replacement and SHBG levels , yes ?

For the 4/29/24 calculation, shouldn't it be 1.8, not 0.18? Also one is in ng, the other in pg, so there is a factor of 1000 that seems to have disappeared.

Hi, Michael i have a question about niacin you took 60 mg to increst nad but how much is your weigh becuse i want to try it too but maybe low dose that 60 mg beacuse i have only some 51 kg i want to try maybe 21.25 mg nikotynamid and 10 mg niacin and i saw when i take 16mg of nikotynamid i got realy good boost of energy i didnt test that but this is how i feel