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| Image 1: Are you taking copious amounts of synthyroid (levothyroxin, T4), already, and feel as if your hypothyroidism became rather worse than better? Does Your Dr tell you that your TSH is fine and you should just exercise more and eat less to stop gaining weight like mad? Than this post is for you! |
The issue of optimal thyroid medication resurfaced as of late on the
SuppVersity facebook wall, when I posted the link to a recently conducted retrospect study in patients who had undergone total thyroidectomy and were now receiving postoperative levothyroxin
only hormone therapy by Ito et al. Not to my personal, but obviously to the researchers surprise, the textbook prescription of the "metabolically inactive" T4 (essentially that is as almost 90% of "general knowledge about thyroid hormone metabolism incorrect as T4 can very well interact with thyroid receptors, it is though TR-alpha specific and has little metabolically activating effects, cf. Koury. 2009)
did not suffice to restore the circulating levels of the active thyroid hormone T3 to the preoperative levels (Ito. 2012). Only when so much T4 was administered that the thyroid stimulating hormone (TSH, also known as thyrotropin) were "suppressed" (as per textbook definition) the circulating T3 levels got back within the physiological normal range.
"Nurse, send the patient home and show me his lab report!"
The real-life consequences of treating lab values instead of patients and going by textbook prescriptions instead of the often debilitating symptoms of hypothyroidism which range from
- physical problems such as weight gain, constipation, constant cold, feeling of cold, blurred vision, nausea, sleepiness, low blood pressure, high cholesterol and blood glucose levels, etc. to
- psychological issues such as general cognitive decline, inability to concentrate, mental fatigue, anger, confusion and depression
and often become rather worse than better, when patients who still have their thyroid gland are going on "partial replacement" or start taking a "supportive" dose of synthyroid (levothyroxin, T4) to help a sluggish thyroid along.
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| Image 2: Ladies, you are lucky you got all that subcutaneous fat to absorb those lubricants and PCB laden cosmetics you are using and stash it away ... a pity it's all going to haunt you, when you want to get rid of those fatty, unaesthetic dumping grounds. |
Weight loss and thyroid function: Beyond overdieting and undereating While those two, i.e. training like mad and eating like too little or only protein are unquestionably the main culprits, when it comes to diet-induced thyroid malfunction (in this cases thyroid medication is by the way counter-indicated; T4 would not work, T3 would simply burn away even more muscle mass), there is another interesting phenomenon you maybe have not heard about:
Self-intoxication! Well, at least this is how I would call the sudden drop of thyroid function that is only one of the nasty effects the release of organochlorines, which have accumulated in the fat tissue of the dieters over years and are now liberated within months, in morbidly obese patients on "zero calorie" diets often weeks, has on the whole endocrine system of formerly big losers (Pelletier. 2002; Tremblay. 2004; Hue. 2006). Pelletier et al. for example found statistically significant
negative correlations between the circulating levels of active thyroid hormone T3 and the amount of ...
- hexachlorobenzene (HCB), which was used as a pesticide until 1965 and was also
used in the production of rubber, aluminum, and dyes and in wood preservation and is currently formed as a byproduct during the manufacture
of other chemicals, mainly solvents and pesticides, and
- PCB 156, one of the members of the olychlorinated biphenyl (PCB) family of chemicals that has now been banned from industrial
insulators and lubricants, because of substantial evidence of its carcinogenic and neurotoxic effects.
... And you bet that this is only the tip of an iceberg. After all, fat is not just a storage site for useful energy, it is also the dumping ground for everything fat soluble you better lock away so that it cannot harm important organs; now, when you think about that, it stands to reason why the fat of animals that have been fed corn or whatever else that's been exposed to one or another of these compounds probably actually
is, as common "wisdom" says, associated with an increased cancer risk and all sorts of other ailments.
What most doctors either don't know or simply ignore is the fact that the
thyroid produces T3 and T4 at a very specific natural ratio of about 100/6 (I deliberately did not cancel the fraction, and wrote 50/3, instead, because 100/6 is the thyroid's daily production of T4/T3 in mcg, the rest of the approximately 20mcg of T3 come from local deiodinase processes at in other organs). Now, if we simply add say 50µg of T4, the corresponding decline in TSH will reduce the overall thyroid hormone output from the gland; and though the exact degree of "suppression" will depend on absorption kinetics, inter-individual differences, the presence / absence of inflammation and the specific activity of deiodinase enzymes which convert T4 to either T3 or reverse T3 (rT3) in the peripheral organs (esp. the liver and the kidneys), we will at this point simply assume that corresponding to the daily T4 output of 100µg the 50µg dose will suppress the total (T4+T3) output of thyroid hormones by ~50%:
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| Figure 1: Illustrative "calculation" of the effects of partial thyroid hormone replacement with 50mcg T4 only. |
As my example calculation in
figure 1 shows, this would equal
a reduction of roughly -10% in terms of thyroid hormone activity and that despite the fact that the textbook will tell you that it would not make a difference. That I write "roughly" and not "definitively" is yet quite important, here, as there are too many confounding factors, such as the...
... which will eventually determine both, the hormone production, as well as its metabolic effects to make
any clearcut statement. Unfortunately, the same is true, but rarely appreciated for the success of the standard (T4 only) treatment for hypothyroidism, the efficiacy of which will likewise vary from person to person and is even highly susceptible to fluctuations and changes in body weight, inflammation, macro- and micronutrient content of the diet etc.
Against this background, it stands to reason that the argument
"but it works for most of my clients" you will often hear from your Dr. is of little significance for you as an individual and even a statement like "but didn't you feel better, when we initiated the treatment 2 months ago" could not just be missing the boat, altogether, but brings another commonly overlooked problem to mind: If you have been suffering from symptoms of hypothyroidism for a couple of years, you would probably feel "major improvements" if you went from a "1" as in "very bad" to a "3" as in "bad", without knowing that you may, just as the majority of the subjects in a study that's been published in
The New England Journal of Medicine in 1999, feel even better if you received 12.5mcg of T3 instead of 50mcg of the T4 your Dr. has prescribed.
T4 + T3 therapy makes subjects feel better, 20/32 don't want to go back on monotherapy
The 31 hypothyroid patients who took part in the 10-week study during which the participants received in random order either their regular "T4 only" thyroid medication (e.g. 200mcg of T4) or an identically looking combination preparation in which 50mcg of the original T4 dosage had been replaced with 12.5mcg of T3 (e.g. 150mcg T4 + 12.5mcg T3). The patients, 31 women and 2 men with a mean age of 46 years and either autoimmune thyroiditis or thyroid cancer that was treated with baseline doses of 75±53 µg T4 per day (range 100-300 µg), were closely monitored during the both of the 5-week interventions and biochemical, physiologic, and psychological tests were performed at the end of each treatment period.
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| Figure 2: Cognitive performance and psychological well-being of the 32 subjects of the
Bunevicius study assessed by standardized tests on either regular T4
only or T4 and T3 combination protocols (based on Bunevicius. 1999) |
A cursory glance at the subjects' "objectively" measured cognitive performance (
figure 2, left) and
pyschological well-being (
figure 2, right) does already reveal that there were statistically improvements in a host of parameters that are of unquestionably greater importance to your daily life than an "optimal" level of thyroid stimulating hormone.
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| Figure 3: Mood and physical symptoms in the 32 subjects of the Bunevicius study assessed by straight forward questionnaires with visual analogue scales - this is the "how do yo actually feel" data (based on Bunevicius. 1999) |
If you combine that with the information the patients provided on a visual analogue scale questionnaire on their perceived psychological and physiological well-being, where every single test result spoke in favor of the combination therapy(!), it is thus not very surprising that
[w]hen asked at the end of the study whether they preferred the first or second treatment, 20 patients preferred thyroxine plus triiodothyronine, 11 had no preference, and 2 preferred thyroxine alone (P=0.001).
These results were unrelated to the order of treatment and the two patients who preferred the T4 only treatment had probably ended up slightly hyperthyroid as they were complaining of feeling "slightly nervous during combined treatment" (Bunevicius. 1999). The others however emphasized that they "noticed that they were more energetic, had better concentration, and simply felt better" (ibid.) than on T4 alone.
The Bunevicius study in nuce
Protocol Reduce T4 intake by 4mcg per 1mcg of T3 you introduce; optimally reduce T4 intake by 50mcg and att 12.5mcg of T3 in.
Results Thyroid hormone levels staid in range (see table above), the +3beat/min increase in pulse rate is harmless and the non-significant drop of 6 and 2pts in systolic and diastolic blood pressure is nothing to speak of.
| T4 | T4+T3 |
| TSH (µU/ml) | 0.8 | 0.5 |
| TSH = 0* | 7 | 5 |
| T4 (µg/dl) | 15.2 | 11.3 |
| T3 (ng/dl) | 87 | 117 |
Table 1: Serum levels of selected hormones and *# of patients with serum TSH <0.05µU/ml
Side Effects Two subjects felt slightly agitated on T4 + T3, no other side effect were reported
Useful for people who are taking high (>>50mcg) doses of T4 (only under supervision of your Dr!)
Not useful for people who don't need thyroid medication and simply suffer from low thyroid hormone due to overtraining, undereating or both (see links below).
Implications: Especially the usually overlooked effects on mood, cognitive function and "subjective" well-being, or rather the negative effects T4 only treatment has on these parameters, do speak in favor of putting the
unwarranted prejudice against the "myotoxic" (=heart damaging) T3 overboard. We are, after all, not talking about the induction of full-blown hyperthyroidism, the detrimental effects of which on the hearts of rodents are essentially what brought the myth of the "dangerous T3" to live; we are just talking about
doing our best to emulate the natural balance, which is
not adequately and reliably measurable by taking the thyroid stimulating hormone (TSH) levels in the blood of a patient as your only reference.
Moreover, the notion of "just throwing in T4 and waiting for the target tissue to produce as much T3 from it as needed" is intrinsically flawed as it negates the established exogenous T3 requirements of the mammalian brain (~20% of the T3; cf. Silva. 1984), as well as the local downregulation of the T4 => T3 conversion in the brain upon exposure to elevated serum thyroxine (T4) levels (Silva. 1985), as they will occur whenever you simply "up the dosage" of levothyroxine in the false belief that this would help you to get rid of persistent symptoms of hypothyroidism. Against that background it appears to be rather the exception than the norm that you would be optimally functioning on T4 only and not end up
- still systemically hypothyroid with even lower serum T3 levels (or T3-to-rT3 ratios), than before, or
- now centrally (in the brain) hypothyroid despite "normal" or even suppressed TSH levels and adequate or high circulating thyroid hormone levels
Against that background, the researchers conclusion that the "ideal replacement regimen [especially] when thyroid-gland function is absent or nearly absent might consist of 10 µg of triiodothyronine daily in sustained-release form (because the hormone is rapidly absorbed and metabolized), along with enough thyroxine to ensure euthyroidism" (Bunevicius. 1999) does appear reasonable, although the necessity and value of "sustained" release formulas is certainly debatable, esp. for lower doses of T3.
References:
- Bunevicius R, Kazanavicius G, Zalinkevicius R, Prange AJ Jr. Effects of
thyroxine as compared with thyroxine plus triiodothyronine in patients with
hypothyroidism. N Engl J Med. 1999 Feb 11;340(6):424-9.
- Clur A. Reverse tri-iodothyronine as part of alpha 2 adrenergic receptors. Med
Hypotheses. 1986 Nov;21(3):281-92.
- Hue O, Marcotte J, Berrigan F, Simoneau M, Doré J, Marceau P, Marceau S, Tremblay A, Teasdale N. Increased plasma levels of toxic pollutants accompanying weight loss induced by hypocaloric diet or by bariatric surgery. Obes Surg. 2006 Sep;16(9):1145-54.
- Ito M, Miyauchi A, Morita S, Kudo T, Nishihara E, Kihara M, Takamura Y, Ito Y,
Kobayashi K, Miya A, Kubota S, Amino N. TSH-suppressive doses of levothyroxine
are required to achieve preoperative native serum triiodothyronine levels in
patients who have undergone total thyroidectomy. Eur J Endocrinol. 2012 Jun 18.
- Koury EJ, Pawlyk AC, Berrodin TJ, Smolenski CL, Nagpal S, Deecher DC. Characterization of ligands for thyroid receptor subtypes and their interactions with co-regulators. Steroids. 2009 Feb;74(2):270-6.
- Ruhla S, Arafat AM, Weickert MO, Osterhoff M, Isken F, Spranger J, Schöfl C,
Pfeiffer AF, Möhlig M. T3/rT3-ratio is associated with insulin resistance
independent of TSH. Horm Metab Res. 2011 Feb;43(2):130-4.
- Silva JE, Matthews PS. Production rates and turnover of triiodothyronine in rat-developing cerebral cortex and cerebellum: responses to hypothyroidism. J Clin Invest 1984;74:1035-49.
- Silva JE, Leonard JL. Regulation of rat cerebrocortical and adenohypophyseal type II 5'-deiodinase by thyroxine, triiodothyronine, and reverse triiodothyronine. Endocrinology 1985;116:1627-35.
- Tremblay A, Pelletier C, Doucet E, Imbeault P. Thermogenesis and weight loss in obese individuals: a primary association with organochlorine pollution. Int J Obes Relat Metab Disord. 2004 Jul;28(7):936-9.
