T3 vs. T4.... what's the difference between them?

[satchboogie]

i hear that T4 isnt nearly as strong as T3...

would taking a high dose of T4 be close to the effects of T3?

is T4 as risky, more risky, or less risky than T3?

 

[Zeca]

L-thyroxine (T4)

This drug is normally used as a replacement therapy in congenital or acquired hypothyroidism and it’s also used to suppress TSH in cases where a person is suffering from hyperthyroidism. It’s released in a 20/1 ratio in respect to T3. T4 is less potent than T3, metabolically speaking, and has a half life of six to seven days in euthyroid humans. (That’s where a person’s thyroid gland is enlarged but it’s not associated with inflammation or cancer. Also called goiter.) The brand name of T4, when it’s bought from the pharmacy, is Synthroid.


L-triiodothyronine (T3)

This drug is also used to treat hypothyroidism and is even used to determine if someone has hyperthyroidism. It’s said to be three to five times more metabolically potent than T4 and has a half-life of £ 2.5 days. Brand names are usually Cytomel or Cynomel. The usual dosages used to treat hypothyroidism are 5 to 25 mcg daily and gradually increasing the dosage to 60 to 75 mcg daily. Some people need as much as 100 mcg daily — 20 to 25 mcg of T3 is approximately the same as 100 mcg of T4.

t3 is more potent than t4...... so more risky

 

[Citruscide]

From what I've read T3 is 4-5 times more potent than T4... but as produced in the body, I'd have to disagree with the half-lives... T3 (L-triiodothyronine) has a half-life of 1-2 days, where as T4 (L-thyroxine) is elimited slowly from the body and has a half-life of around 6-7 days.

To put it in laymen's terms... Both T3 and T4 are synthesized and secreted from a normally functioning thyroid. The Thyroid produces these hormones because it is stimulated by an action called thyrotropin, or Thyroid Stimulating Hormone (TSH), which is produced in the front of the pitutary gland (which, consequently regulates the thyroid production ... in laymen's terms).

Going further, the TSH is regulated by the hypothalimus by production of a thyroid releasing hormone (TRH), and probably other mechanisms as well. T-hromones in the blood act as a signal to inhibit any over-production of t3/t4. I can go on... but i think the general picture is given here.

T3/T4 work by enhancing the oxygen consumption of many of the body's tissues... they increase the BMR and metabolism of carbs, proteins and fats... this has a great influence on the organs and development of the central nervous system... they also help the free flow of blood flow by increasing the contractability of blood flow...and decreasing resistance that can occur.

Ok... i'm done with science talk...

As I said, both of these will increase your BMR and metabolism of the macronutrients you eat... diet can be a little more sloppy on these drugs, because your freaking metabolism is out of control.

I don't see why you would take these together... T4 is a great treatment for people with fibermyosis (sp?)... but other than that... T3 is more used by the bodybuilding community because of it's strength and potency.

Becareful about using these drugs... as you'll have to taper it down accordingly to avoid any sort of rebound/springy effects from your thyroid.... I've known women, especially, who had their thyroids "reset" to keep their natural bodyweight up 10lbs... not good.

this post is all over the place... I apologize... I started on how the process worked, before I realized what the question was...

C-ditty

 

[satchboogie]

does t4 have any use in bodybuilding?

 

[ChefWide]

bump

 

[satchboogie]

boy thats an old post but still is interesting... more feedback is always good.

 

[geopharm]

if your dieting the problem will be t4 to t3 conversion so simply increasing available t4 won't be of much benefit.

although most t3 produced in thyroid gland some is converted from t4 in the liver.

for bb cutting purposes u want t3 !

 

[GoldenDelicious]

hi

T3 and T4 both work similarly (virtually interchangeably really) although the brain has a slight preference for T4. in practice the difference is irrelevant really

when you use these drugs you only really use them for replacement of the hormones in people with thyroid deficiency

you can also use them for a couple of cancers but i dont want to get into that because im tired and we all dont give a toss anyway

the main difference between them is the onset of action, and duration of action

T3 starts working faster, but only lasts 2 or 3 days

T4 takes longer to kick in, but lasts 2 or 3 weeks

logically therefore T4 is the drug of choice because it lasts longer for people who need long term replacement

T3 is used if you need to bump up levels quickly, and/or need to drop the dose quickly (lets say you want to do a baseline check or something you give t3 so that levels go back to normal quickly and you dont inconvenience the patient, rahter than making them suffer low levels for 3 weeks while the t4 gets out of your system)

thyroid hormones arent the best thing to take to cut since inevitably you get a bit of a rebound, and you have to watch out you dont become dependant otherwise this rebound will be a lot worse. therefore you need to taper the dose down when you get off it

as for you guys discussing potencies- that all doesnt really matter to be honest, since t3 will come in 20 mcg tablets or something while t4 will come in 100mcg tablets, and costs will be about the same on a per tablet basis. it all eqals out in the end

cheerios

 

[lartinos]

what else can be taken to make the rebound not as bad? Liporexin?

 

[GoldenDelicious]

what else can be taken to make the rebound not as bad? Liporexin?

a lower dose of the thyroid meds

proper tapering down

shorter cycles

other drugs which burn fat may offset fat gain but all they will do is mask the true hypothyroidism which has been induced by supplementing the hormones (ie the rebound itself)