Study that shows T3 & T4 degrease glycogen synthesis/storage
- 05-28-2006, 09:44 PM
Study that shows T3 & T4 degrease glycogen synthesis/storage
I had read this in various T3 articles, but what unable to find a study that supported it until recently.
Low muscle and liver glycogen contents in dogs treated with thyroid hormones.
Brzezinska Z, Kaciuba-Uscilko H.
Muscle biopsies for glycogen determinations were taken from dogs before (controls) and after prolonged treatment with thyroid hormones (T4 or T3). The glycogen content in quadriceps femoris was measured before exercise, immediately after its cessation, and during 24h of post-exercise recovery. The effect of thyroxine treatment on the liver glycogen content both at rest and following physical effort was also studied. A marked decrease in the muscle glycogen content determined at rest was found both in T4 and T3-treated dogs in comparison with controls. Physical exercise diminished the muscle glycogen store to similar values in control and thyroid hormone-treated dogs, but the rate of the muscle glycogen utilization during exercise was lower in the latter. The rate of the post-exercise muscle glycogen synthesis was considerably inhibited in thyroid hormone-treated dogs, but 1 hr glucose infusion, applied immediately after cessation of exercise, accelerated the rate of glycogen re-synthesis, so it was close to that in controls without infusion. Thyroxine treatment also affected the liver glycogen store. Both at rest and after physical exercise significantly lower liver glycogen contents were found in T4-treated dogs than in controls.
- 05-29-2006, 11:05 PM
Here's a good study that shows the relationship between T3, glycogen, and insulin.
The effects of hyperthyroidism on the sensitivity and responsiveness of glycolysis and glycogen synthesis to insulin were investigated in the isolated incubated soleus muscle of the rat. Hyperthyroidism, which was induced by administration of tri-iodothyronine (T3) to rats for 2, 5 or 10 days, increased fasting plasma concentrations of glucose, insulin and free fatty acids. Administration of T3 for 2 or 5 days increased the rates of glycolysis at all insulin concentrations studied: this was due to increased rates of both glucose phosphorylation and glycogen breakdown, but there was no effect of T3 on the sensitivity of glycolysis to insulin. However, administration of T3 for 10 days increased the sensitivity of the rate of glycolysis to insulin. The concentration of adenosine in the gastrocnemius muscles of the rats was not different from controls after 5 days, but it was markedly decreased after 10 days of T3 administration. If these changes are indicative of changes in the soleus muscle, the increased sensitivity of glycolysis to insulin found after 10 days' T3 administration could be due to the decrease in the concentration of adenosine. Administration of T3 decreased the sensitivity of glycogen synthesis to insulin and the glycogen content of the soleus muscles. This may explain the decreased rates of non-oxidative glucose disposal found in spontaneous and experimental hyperthyroidism in man. The rates of glucose oxidation did not change after 2 days, but they were increased after 5 and 10 days of T3 administration.
- 05-30-2006, 09:38 PM
My brains not functioning fully at the moment. What exactly does this mean for those of us taking T4?? Should we eat more carbs, less carbs, stay the same??
05-30-2006, 10:42 PM
when on any thyroid replacement - you need to watch your carbs, if you consume too little - you will drag ass.,
05-30-2006, 11:18 PM
I assume it depends on what kind a diet you want to follow. Basically your going to feel like your on a low carb diet with flat and weak muscles. To answer your question, i don't know. I tried it with an increased number of carbs and it didn't help. Glycogen lowering is however dose dependant, and i have read that this can be avoided if the level of T3 in circulation stays below ~37 mcg's, although i haven't found literature to confirm this yet.Originally Posted by CRUNCH
I will give a personal account on this in a couple of weeks. I've been on T3 for a few weeks now at dosages upto 100 mcg/day and feel as weak as a kitten, but starting today i have lowered the dosage to ~35 mcg and hope i see my strength return to normal. Sorry for not being able to give you straight answer.
05-30-2006, 11:58 PM
I also just started T4 last Friday. Per Dr D, I am doing 25mcg per day for the first week, then upping it by 25mcg per day every week. Other than feeling a little warmer than usual a few times per day, I haven't noticed anything else, but dosage is still low. We'll see in a month when I'm up to 100 mcg, or 150 in 6 weeks.Originally Posted by Schwaugher
05-31-2006, 12:16 AM
What it means is obvious, when you take T4 & T3 your metabolism is higher, therfore your burning cals at a higher rate before they can become stored as fuel, now with that said, this can only happen if you are restricting your diet, they fail to tell you what the diets were in these dogs.
I take both for a low thyroid for 13 years, when you are eating properly you will still get your glycogen stores supplied adequately, over eat continuously and yes, you can still get fat while taking these drugs.
Everything effects the body, how much exercise, food, and your general health have alot to do with how these drugs will help you.
05-31-2006, 11:38 AM
Here's one on humas that takes into consideration a dosage of 100 mcg/day as well as exercise, protein synthesis and breakdown, along with muscle oxidative capacities. I found it very interesting that protein synthesis was increased 9% and protein breakdown was increased 12%, so the total lost of muscle protein would be 3% above the norm. I wondering if a low dose T3 cycle would yield the same protein systhesis rate without the increase in catabolism?
Exercise Capacity and Hyperthyroidism
Full Text: http://www.pubmedcentral.gov/picrend...8&blobtype=pdf
To investigate the mechanism of reduced exercise tolerance in hyperthyroidism, we characterized cardiovascular function and determinants of skeletal muscle metabolism in 18 healthy subjects aged 26±1 yr (mean±SE) before and after 2 wk of daily ingestion of 100 pg of triiodothyronine (T3). Resting oxygen uptake, heart rate, and cardiac output increased and heart rate and cardiac output at the same submaximal exercise intensity were higher in the hyperthyroid state (P < 0.05). However, maximal oxygen uptake decreased after T3 administration (3.08±0.17 vs. 2.94±0.19 l/min; P < 0.001) despite increased heart rate and cardiac output at maximal exercise (P < 0.05). Plasma lactic acid concentration at an equivalent submaximal exercise intensity was elevated 25% (P < 0.01) and the arteriovenous oxygen difference at maximal effort was reduced (P < 0.05) in the hyperthyroid state. These effects were associated with a 21-37% decline in activities of oxidative (P < 0.001) and glycolytic (P < 0.05) enzymes in skeletal muscle
and a 15% decrease in type 11A muscle fiber cross-sectional area (P < 0.05). Lean body mass was reduced (P < 0.001) and the rates of whole body leucine oxidation and protein breakdown were enhanced (P < 0.05). Thus, exercise tolerance is impaired in short duration hyperthyroidism because of decreased skeletal muscle mass and oxidative capacity related to accelerated protein catabolism but cardiac pump function is not
reduced. (J. Clin. Invest. 1991. 88:2047-2053.)
05-31-2006, 11:52 AM
Originally Posted by Schwaugher
yes, but that is for Hyperthyroid, there is also hypothyroid. People with hyper, for long periods will start burning muscle if they do not eat correctly.
05-31-2006, 08:17 PM
Sorry but I don't understand the point your trying to get accross. My diet is in check just like it always is. And if i use T3, it will induce hyperthyroidism, hypothyroidism is irrelevant. Everyone will start burning muscle if they don't eat correctly while dieting. Your assuming my goal is weight loss which it isn't. The goal i was trying to accomplish with this thread is how to prevent glycogen breakdown and catabolism that happen at high dosages of T3. The only solution i can think of is to use a lower dose of T3 during bulking, cutting, or maintaining.Originally Posted by FitnFirm
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