Medications and lab tests

T3 and T4
This was posted a few weeks ago but I can't find the thread.

From my limited understanding of testing the thyroid (I also have hypothroidism), the labs rarely test for T3 and T4 because there is no conclusive test that is available or everyone agrees on.

I wish I could find the thread regarding this subject. Quite a few people contributed what they had learned and found out about it.

BTW, for my hypothyroidism, my doctor put me on low-dose (lowest possible dose) of Synthroid. Seems to have jump-started my thyroid back up to within-normal-limits and my energy levels are coming back as well.

palmyrafan said:

T3 and T4
This was posted a few weeks ago but I can't find the thread.

From my limited understanding of testing the thyroid (I also have hypothroidism), the labs rarely test for T3 and T4 because there is no conclusive test that is available or everyone agrees on.

I wish I could find the thread regarding this subject. Quite a few people contributed what they had learned and found out about it.

BTW, for my hypothyroidism, my doctor put me on low-dose (lowest possible dose) of Synthroid. Seems to have jump-started my thyroid back up to within-normal-limits and my energy levels are coming back as well.

thyroid pannel
A complete thyroid panel test will include

Hypersensitive thyroid-stimulating hormone (TSH)
free thyroxine (fT4)
free triiodothyronine (fT3)
reverse T3 (rT3)
anti-thyroglobulin antibodies (anti-TG)
anti-thyroid peroxidase antibodies (anti-TPO)
Saying that they normally will not spend that much money on you
Normally they test me for (as it appears on my lab tests)

Thyroxine free ... or... free thyroxine (fT4)
thyrotropin ... or ...Hypersensitive thyroid-stimulating hormone (TSH)
Thyroglobulin ... or ... Thyroglobulin (Tg) (used to determine if my body is producting thyroid hormones itself.. simple cancer check for people with a TT)
Thyroglobulin Ab ... or ... Thyroglobulin antibody (TgAb) (for the same reasons as Tg)

the other tests that don’t get routinely done are

free triiodothyronine (fT3) ... since you don’t have a thyroid fT3 is based off the fT4 relationship

Reverse T3 (RT3 or REVT3) is a biologically inactive form of T3. they will normally test for fT3 and/or fT4 instead.

---
For Myself I am going to be talking to my doctor about being tested for fT3 as well as fT4 since I am on a Synthroid / Cytomel combination. For anyone only on synthroid they will probably only test fT3 once to make sure it is in proportion to your fT4.

---
As Thyroid cancer survivors, we should regularly be tested for
Hypersensitive thyroid-stimulating hormone (TSH)
free thyroxine (fT4)


as for was I hypo before/during thyroid cancer ... YES most defiantly.

thank you for brining this topic up it has made me realize that most of us should have our fT3 tested every few times they do a fT4 (and every time for people on Cytomel as well)... Now comes the hard part convincing the doctors.

---
Looking back through my labs from when they started testing (before they knew i had cancer) they kept telling me I was in NORMAL thyroid ranges but they NEVER checked for fT3 until after they removed the thyroid, and then they only did it once. So I am only guessing I had a low fT3 level because of how I was feeling at the time

And yes I have a full set of my lab reports both at home and at work so I can reference them when trying to answer questions :P

Craig

3boys_mom said:

Hypo
Craig,
I found a great analogy online about how the thyroid works--the thyroid is the AC/heater and the pituitary gland is the thermostat, and I forget what they said the person adjusting the thermostat was (maybe the hypothamlus). Anyway, they pituitary turns on and off every time it reaches a certain "level". Since the TSH test is a test to see if the pituitary is doing its job, it's not very effective for detecting if the AC (thyroid) is low on freon (hormone) and running constantly or not at all.

For many people, by the time their TSH levels are not within range, the thyroid is worn out and needs a repair man or replacing. I don't understand why the doctors can not figure this out and stop testing only for TSH.

I was also wnr with my TSH, but felt horrible! I was losing my hair, my muscles were weak--a long list of things. My dr. tested my fT3 and sure enough it was really off.

I am now on a Synthroid/Cytomel mix (along with anti-depressants, which I love to get off of) and feeling a lot better--except for this large lump in my throat. :-)

I hope your appointments go well today!

Sarah

haven’t gotten to my Endo to convince him I needed my fT3 tested... lucky for me i have a very easy PCP and I was able to bully into about 8 blood tests including the fT3... I know it’s not the right way to get it done but taking charge and pushing it though then I can show the results to my Endo instead of trying to convince him.

At least I don’t have to worry about the lump in my throat.

As far as t4 being normal while t3 being low...

--- Cut and paste time --- http://www.salugenecists.com/genpage.php?tname=disease&dbid=21

The thyroid produces two main hormones: T4, the least active form, and T3, a much more active hormone primarily responsible for regulating cellular metabolic activities. The production of both T4 and T3 is carefully controlled by the thyroid’s overseers, the pituitary and hypothalamus, two endocrine glands located in the brain. As T3 levels drop in the blood, the hypothalamus secretes TRH (thyrotropin-releasing hormone), a signaling hormone that notifies the pituitary to secrete TSH (thyroid-stimulating hormone). As its name implies, TSH stimulates the thyroid gland to produce T4 by combining iodine with the amino acid tyrosine. This results in the production of approximately 90% of the body�s T4 and 10% of its T3. (T4 is tyrosine plus 4 iodine molecules, while T3 is tyrosine plus three iodine molecules.) If the hypothalamus fails to secrete TRH, the pituitary's fail-safe system takes over. The pituitary checks up on the hypothalamus by sampling the amount of T3 passing through its own circulation as it converts inactive T4 into T3. If its T3 levels drop, the pituitary gland secretes TSH, which triggers the thyroid to produce and release T4, thus quickly rectifying the situation.

Once T4 is in the blood, another part of the body's network takes over, using cortisone, a hormone secreted by the adrenal gland, to convert T4 to T3 in the peripheral tissues, primarily the liver and kidneys, from which T3 is sent into the bloodstream.

Although now circulating to cells throughout the body, T3 has still not reached its final target, the interior of the cells where T3 affects metabolic functions. To complete its job, T3 must pass through the cellular membranes and connect with the right receptor sites to gain entry into the mitochondria (the tiny energy production factories within each cell) and/or the cell’s nucleus.

Finally, effective thyroid function faces one other potential internal roadblock: cytokines. Hormone-like substances secreted by various types of cells, cytokines direct immune responses and act as messengers in cell-to-cell communication. Some cytokines directly affect the hypothalamic-pituitary-thyroid axis and are capable of blocking the conversion of T4 to T3.

Conditions outside the body can also affect thyroid function. When the diet does not contain adequate amounts of iodine, the thyroid cannot produce T4. When this occurs, the thyroid enlarges, swelling into a goiter, the typical sign of hypothyroidism in the developing world where iodine deficiency is common. Long-term stress, which depletes the adrenal glands stores of cortisone, can also cause a problem. Even if the thyroid gland produces sufficient amounts of T4, so blood tests of T4 levels (the test commonly used to evaluate thyroid activity) appear normal, if insufficient cortisol is available in the liver and kidneys where it is used to convert T4 to T3, metabolism will slow down. High levels of cytokines may also play a role here since certain cytokines prevent the conversion of T4 to T3.

----------

So if your t4 is normal and t3 is low they need to check cortisol and cytokines...

------http://en.wikipedia.org/wiki/Cortisol----
Cortisol
Not to be confused with cortisone, a similar compound with a similar name, genesis, and function.

Cortisol (hydrocortisone) is a steroid hormone, or glucocorticoid, produced by the adrenal gland.[1] It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat, protein and carbohydrate metabolism.[2] It also decreases bone formation. During pregnancy, increased production of cortisol between weeks 30-32 initiates production of fetal lung surfactant to promote maturation of the lungs. Various synthetic forms of cortisol are used to treat a variety of diseases.
-----http://en.wikipedia.org/wiki/Cytokines---

Cytokines (Greek cyto-, cell; and -kinos, movement) are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication. Cytokines can be classified as proteins, peptides, or glycoproteins; the term "cytokine" encompasses a large and diverse family of regulators produced throughout the body by cells of diverse embryological origin.[1]
-----
Ok going to have to research this some more to figure this one out

As far as why doctors test for TSH and fT4 only it is a real simple thing that happens all the time with everyone. The doctors only think one thing is going to go wrong at a time.

And this is the reason we need to be our advocates... I joke all the time about my body's warranty expired.

Right now I am
1) Thyroid cancer survivor
2) Dealing with Vertigo
3) Had 2 hearing operations
4) Sleep apnea
5) Weight issues
6) forgetfulness/brain fog
7) Bad knees/back/shoulder/neck
8) Overweight
9) Calcium/magnesium/vitamin D deficient
10) High blood pressure
11) Stress (see 1-10)

I am sure I am forgeting a few things, but here is the problem as my PCP states they do not deal with laundry lists they only deal with 1 or 2 things per visit.
Personaly looking over the list of things I figure more than 2 of them are probably related

well off to the VA to turn in 18 inches of my medical recoard (and 3 cd's of xrays and the like)

at least they are on my side to get everything documented and tested.