The T4/T3 ratio changes with age
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Thyroid hormones were not included in Dr. Peat's article Progesterone Pregnenolone & DHEA - Three Youth-Associated Hormones. After reading the linked article below, I think one might consider the T4/T3 ratio to have youthful ranges as well. Thyroid hormones are complicated. For my gender and age, I would not consider supplementing with T4 only.
The hypothalamic–pituitary–thyroid (HPT) axis is fundamental to human biology, exerting central control over energy expenditure and body temperature. However, the consequences of normal physiologic HPT-axis variation in populations without diagnosed thyroid disease are poorly understood. Using nationally representative data from the 2007 to 2012 National Health and Nutrition Examination Survey, we explore relationships with demographic characteristics, longevity, and socio-economic factors. We find much larger variation across age in free T3 than other HPT-axis hormones. T3 and T4 have opposite relationships to mortality: free T3 is inversely related and free T4 is positively related to the likelihood of death. Free T3 and household income are negatively related, particularly at lower incomes. Finally, free T3 among older adults is associated with labor both in terms of unemployment and hours worked. Physiologic TSH/T4 explain only 1.7% of T3 variation, and neither are appreciably correlated to socio-economic outcomes. Taken together, our data suggest an unappreciated complexity of the HPT-axis signaling cascade broadly such that TSH and T4 may not be accurate surrogates of free T3. Furthermore, we find that subclinical variation in the HPT-axis effector hormone T3 is an important and overlooked factor linking socio-economic forces, human biology, and aging.
Am I missing soemthing important?
"Without a realistic view of where you are, you can't expect to go anywhere." Ray Peat (1936-2022) 👀
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@DavidPS wow
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@DavidPS said in The T4/T3 ratio changes with age:
Am I missing soemthing important?
High level T4 means you don't convert T3 well.
So I won't say old people with high level T4 are positively associated with mortality in old age. It's the sign sth goes wrong. High level T4 should be seen as the witness of a problem: A low thyroid function.
And as reminder: TSH is an indirect link: It only tell us how the brain perceives the situation.
PS: If fT4 is high and fT3 low, we should consider rT3 to confirm the problem of conversion. -
also, higher TSH correlates with longer life as one gets older.
https://academic.oup.com/jcem/article/100/10/3806/2835801
Context:
Longevity is associated with changes in circulating levels of thyroid hormone (TH) and/or TSH in animals and humans, but underlying mechanisms remain elusive.Objective:
We explored in 38 offspring of nonagenarian participants from the Leiden Longevity Study, who are enriched for longevity and in their partners, ultradian and circadian rhythmicity of TSH, temporal relationship, and feedback and forward interplay between TSH and TH.Methods:
We collected blood samples every 10 minutes for 24 hours for TSH and TH profiles. We used a deconvolution analysis to estimate basal (nonpulsatile), pulsatile, and other secretion parameters to characterize ultradian rhythmicity and locally weighted polynomial regression of TSH to assess circadian rhythmicity. A cross-correlation analysis was used to investigate the temporal relationship between TSH and TH and cross-approximate entropy to assess feedback and forward interplay between TSH and TH.Results:
Compared with partners, offspring displayed higher mean (95% confidence interval [CI]) basal TSH secretion (34.3 [95% CI 27.2–43.1] mU/L per 24 hours vs 18.5 [95% CI 14.4–23.7] mU/L per 24 hours, P = .001) but no differences in ultradian or circadian properties of TSH. The temporal relationship between TSH and free T3 at zero delay was higher in offspring (0.48 ± 0.2) compared with partners (0.26 ± 0.4) (P = .05), but the feedback and forward interplay between TSH and TH did not differ.Conclusions:
Familial longevity is associated with increased basal TSH secretion and a strong temporal relationship between TSH and free T3 but not with differences in ultradian or circadian TSH rhythmicity or feedback and forward interplay between TSH and TH. -
@LucH said in The T4/T3 ratio changes with age:
If fT4 is high and fT3 low, we should consider rT3 to confirm the problem of conversion.
In addition to issues of conversion, high cortisol my be a root cause of the conversion issue.
“…No, I don't mind at all, but we do have two more callers after you, so go ahead. Real quick, Dr. Peat, you said that when you have higher T3, it can lower T4. Well, if you're under stress, your reverse T3 goes up under the influence of cortisol. And if you lower cortisol, your reverse T3 just naturally goes down. But everything that helps to lower cortisol will help to free up the normal T3 production without reverse T3, and things that can help include sugar and aspirin and B vitamins and minerals. Thank you very much.”
https://www.bioenergetic.life/clips/67a48?t=2836&c=66
Peatbot: To reduce cortisol, consider the following strategies:
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Engage in Relaxing Activities: Activities such as playing a musical instrument, painting, or simply spending time outdoors can help reduce stress and lower cortisol levels. Taking time to relax, like laying on a blanket and watching clouds, can also be beneficial.
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Exercise: Physical activities like chopping wood or using dumbbells can be effective. Exercise helps use muscles properly, which can prevent them from converting cholesterol into cortisol.
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Nutrition: Maintain adequate nutrition to manage stress hormones. Ensure a balanced intake of carbohydrates, proteins, and minerals like calcium and potassium. For example, consuming orange juice can provide carbohydrates and minerals that help manage stress.
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Supplementation: Consider supplements that support the production of protective steroids like pregnenolone, progesterone, and DHEA, which can buffer against cortisol.
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Manage Blood Sugar: Keeping blood sugar levels stable is a powerful way to reduce stress and cortisol.
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Breathing Techniques: Breathing exercises, such as breathing into a bag, can help increase CO2 levels, which may aid in managing stress and cortisol.
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Sunshine and Nature: Spending time in nature and getting plenty of sunshine can have a calming effect and help lower cortisol levels.
By incorporating these strategies into your lifestyle, you can help manage and reduce cortisol levels effectively.
Interestingly, aging is associated with hgher cortisol.
Peatbot: The context suggests that the main features of aging can be produced directly by administering excessive amounts of cortisol. This implies that cortisol, a stress hormone, may play a role in the aging process. However, it does not explicitly state that cortisol levels naturally increase with age. Instead, it highlights that the physiology of aging overlaps with the physiology of stress, which includes the effects of cortisol. Therefore, while cortisol is associated with aging-related changes, the context does not provide a definitive answer on whether cortisol levels increase with age.
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@Ecstatic_Hamster said in The T4/T3 ratio changes with age:
also, higher TSH correlates with longer life as one gets older.
Yes, this was shown in the figure in my post. Her it is again.
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In todays world, endocrine disruptor chemicals (EDC) are another possible root cause of the changes that occur over time.
Endocrine Disruptors Chemicals: Impacts of Bisphenol A, Tributyltin and Lead on Thyroid Function (2025)
Highlights
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Bisphenol A (BPA), Tributyltin (TBT), and Lead (Pb) are endocrine disruptors (EDC).
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Epidemiological and experimental evidence has shown its effects on thyroid function.
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Mechanisms include disruption of the hypothalamus-pituitary-thyroid (HPT) axis.
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Morphophysiological alterations and oxidative stress were observed in the thyroid.
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Exposure control measures and mitigation of EDC effects need to be implemented.
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Well seen, for the impact of deiodination.
When halogens take the place of iodine on thyroid receptors, it's hard to get the right amount of active hormones (T3).
And the problem is all the more serious / harmful for women: fight between thyroid and breasts to capture circulating iodine. iodal would be then required; not just the RDA (150 mcg; much higher).
A protocol must be followed.
Halogens: Fl > Cl > Br> I. (stronger force of attraction for bromine).
In iodine-sufficient areas, the adult thyroid traps about 60 μg of iodine/day, either from dietary iodine or from iodine released during thyroid hormone therapy.
But much higher for iodine when there is inflammation or an immune reaction (mastocytose).Additional info
Why does bromine displace iodine?
The bromine displaces the iodine from sodium iodide as it is further up in group 7 and therefore more reactive than iodine. Iodine is lower down in group 7 and therefore less reactive than chlorine and bromine.
Electronegative elements have the property to remove electrons form the elements to which, it is attached.
Fluorine is an extremely powerful oxidizing agent.
The oxidizing power of the halogens varies in the order: F2 > Cl2 > Br2 > I2
The order of reactivity is chlorine > bromine > iodine. This is because chlorine could displace bromine and iodine, bromine could only displace iodine, but iodine could not displace chlorine or bromine.
Explaining the trend:
When an element in group 7 takes part in a reaction, its atom's outer shells gain an electron and form negatively charged ions, called anions. The less easily these anions form, the less reactive the halogen.
When the atoms become larger, the outer shell becomes further from the nucleus. The force of attraction between the nucleus and the outer shell decreases. An outer electron is gained less easily. The halogen becomes less reactive.
Source: BBC - Halogen displacement reactions https://www.bbc.co.uk/bitesize/guides/zg337p3/revision/3#:~:text=The order of reactivity is,not displace chlorine or bromine.
