What is TT4 test?
TT4 is a basic index to know whether our thyroid
gland working in normal condition. normally, the range should be 65-155nmol/L.
A normal adult will produce T4 90ug a day. 99.97% of T4 will combine
with protein (0.03% will be free, FT3) so that it will not lost with
urine in kidney. Unless the patient has very serious albuminuria, most
of the combined thyroid incretion and the albumen are reversible. Free
incretions master the metabolism. But the combined incretion will supply
a huge incretion source for the free thyroid incretion, it will not
directly affect the metabolism, but can be alleviant.
When the thyroid incretion level changes, it will not let the thyroid
function changes immediately. There are 3 major combined albumens in
plasm, which are TBG, TBPA and albumin. Among them, 80% to 90% will
combine with TBG. TT4 level also affected by the amount of the proteid
combined with thyroid incretion in the serum other than the status of
the thyroid function status, most affected by TBG.
The factors to increase TT4
1. For the high TGB, pregnancy is a frequent reason. Oral contraceptive,
estrogen treatment, hepatitis, knub which can produce estrogen and lymphosarcoma
can also increase TBG and let the TT4 increase. But the patient’s
FT4 is normal which can distinguish with the hypothyroid.
2. Family TBG increase is the excessive TBG caused by concatenate transmissibility
disease which let TT4 and TT3 increase, while FT4 and FT3 is normal.
3. Psychopathic high T4. Cohen and Swiger report 480 psychopaths. TT4
of 30% of new inpatients increase. Swige report 645 psychopaths. TT4
of 33% increase. FT4I of 18% increase. Low after the disease gets catabatic.
4. Some medicine will cause high T4, like thyroid
incretion preparation, ethylamine iodine ketone, Benzedrine,
heroin, clofibrate. Half of the
patient who has ethylamine iodine ketone will cause high
TT4 and FT4I. It is because ethylamine iodine ketone
can partially stop the transform
from T4 to T3 which increase T4 and let it change to
be the inactive rT3.
The factor to reduce TT4
1. Kidney function exhaust, kidney is the place for Thyroxine to release
ammonia and iodine. Therefore, kidney disease, especially the patients
with kidney function exhaust have low T4. Because such patients lose
albumen day by day term and get cacotrophia so TBG becomes low and then
affect TT4.
2. Hepatocirrhosis cause the decreasing of the combined albumen and
then affect the TT4.
3. Acute mental illness. About 10% patients with acute mental illness
had low TT4. After having the treatment, it will become normal.
4. Serious disease. There is stayer stop the combination of thyroid
incretion and serum albumen in the patients’blood circulation.
Then, their TT3 and FT3 become low, rT3 becomes high,
and TT4 usually becomes low. The major difference between this and hypothyroidism
is
TSH low or normal.
5. Some medicine, such as Benzene barbital, Male
hormone preparation, 5-flurin pyrimidine.
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