View Full Version : T3 and T4 tests

09-05-2005, 08:21 AM
i went to see my nephro 2day for some blood tests, and when i checked my weight i found out that i have gained 3 kilograms since last time i saw him (less than 2 weeks ago)..he also noticed the swelling around my eyes which has only returned again recently.
he ordered t3 and t4 tests, i think they have to do with the thyroid gland, but i don't know why he asked for them.
what do high/low levels of t3 and/or t4 indicate in relation to lupus nephritis anyway? if anyone knows anything please let me know as i'm quite worried.

Thank you,

09-07-2005, 07:10 PM
Was it T3 and T 4 or C3 and C4? They test C32 and C4 because if they are low it indicates active lupus. That could be it.


09-08-2005, 07:09 AM
Hi Dina;
A T3 test helps to determine whether the thyroid is functioning properly. This test measures the amount of triiodothyronine, or T3, in the blood. T3 is one of two major hormones produced by the thyroid gland. It is ordered primarily to help diagnose hyperthyroidism and may be ordered to help monitor the progress of a patient with a known thyroid disorder. The T3 test is usually ordered following an abnormal TSH (thyroid screening hormone - To screen for and help diagnose thyroid disorders; to monitor treatment of hypothyroidism and hyperthyroidism) and T4 test. About 99.7% of the T3 found in the blood is attached to a protein (primarily thyroxine-binding globulin but also several other proteins) and the rest is free (unattached). Separate blood tests can be performed to measure either the total (both bound and unattached) or free (unattached) T3 hormone in the blood. Either the total T3 or the free T3 may be ordered. Since most of the T3 is bound to protein, the total T3 can be affected by protein levels and protein binding ability, but the free T3 is not. T3 testing may be ordered along with thyroid antibodies to help diagnose Graves’ disease, an autoimmune disorder that is the most common cause of hyperthyroidism.

A T4 test is to help evaluate thyroid gland function; to help diagnose hypothyroidism or hyperthyroidism. This test measures the amount of thyroxine, or T4, in your blood. T4 is one of two major hormones produced by the thyroid gland (the other is called triiodothyronine, or T3). The thyroid is a small, butterfly-shaped gland located just below the Adam's apple. This gland plays a vital role in controlling the rate at which your body uses energy. The body has a feedback system that turns thyroid hormone production on and off. When the level of T4 in the bloodstream decreases, the hypothalamus (an organ in the brain) releases thyrotropin releasing hormone, which stimulates the pituitary gland (an organ below the hypothalamus) to release thyroid-stimulating hormone (TSH), which in turn stimulates the thyroid gland to make and/or release more T4. As blood concentrations of T4 increase, the amount of TSH released decreases.

T4 makes up nearly all of what we call thyroid hormone, while T3 makes up less than 10%. Inside the thyroid gland, T4 is produced, bound to a protein called thyroglobulin, and stored. When the body requires thyroid hormone, the thyroid gland produces some T4 or T3 and/or releases stored T4 into circulation. In the blood, T4 is present in a free (not bound) and protein-bound form (primarily bound to thyroxine-binding globulin). The concentration of free T4 is only about 0.1% of that of total T4, but the free T4 is the portion of thyroxine that is active. T4 only becomes an active thyroid hormone when it is converted into T3 in the liver or other tissues.
If the thyroid gland does not produce sufficient T4 (due to thyroid dysfunction or to insufficient TSH), then the affected patient experiences symptoms of hypothyroidism such as weight gain, dry skin, cold intolerance, irregular menstruation, and fatigue. If the thyroid gland produces too much T4, the rate of the patient’s body functions will increase and cause symptoms associated with hyperthyroidism such as increased heart rate, anxiety, weight loss, difficulty sleeping, tremors in the hands, and puffiness around dry, irritated eyes.
The most common causes of thyroid dysfunction are autoimmune-related. Graves’ disease causes hyperthyroidism and Hashimoto’s thyroiditis causes hypothyroidism. Both hyper- and hypothyroidism can also be caused by thyroiditis (thyroid inflammation), thyroid cancer, and excessive or deficient production of TSH. The effect of these conditions on thyroid hormone production can be detected and monitored by measuring the total T4 (includes bound and free portion) or the free T4 (only unbound).
I hope that this information has been helpful :P

Peace and Blessings

09-08-2005, 07:41 AM
Yes, this was really helpful. Thank you! :D

09-08-2005, 07:47 PM

That's great data. Thanks!