USC
ENDOCRINE LABORATORIES
TEST INDEX
THYROXINE,
TOTAL (TT4)
Methodology
Electrochemiluminescence Immunoassay
Performed
Tue, Fri
Reported
Same day
Collect
One 6mL
RT (Min: 4mL RT)
Transport
2 mL
refrigerated serum
(Min: 0.8 mL)
Stability
Stored at 2 - 8°C until
used; Stable if frozen at - 20°C
Unacceptable
Do not use
heat-inactivated samples.
Reference
Range 4.5 -
12.5 µg/dL
CPT
Code 84436
Information:
The hormone
thyroxine (T4) is the main product secreted by
the thyroid gland and is an integral component of the
hypothalamus-anterior pituitary-thyroid regulating system. It has the
function of anabolically influencing metabolism. Thyroxine is formed in
a coupling reaction from two DIT molecules (3,5-diiodotyrosine) in the
thyroid gland. It is stored bound to thyroglobulin in the lumina of the
thyroid follicles and is secreted as required under the influence of
TSH. The major part (>99%) of total thyroxine (T4) in
serum is
present in protein-bound form. As the concentrations of the transport
proteins in serum subject to exogenous and endogenous effects, the
status of the binding proteins must also be taken into account in the
assessment of the hormone concentration in serum. If this is ignored,
changes in the binding proteins (e.g. due to estrogen-containing
preparations, during pregnancy or in the presence of a nephritic
syndrome etc.) can lead to erroneous assessments of the thyroid
metabolic state.
The determination of T4 can be utilized for the following indications:
the detection of hyperthyroidism, the detection of primary and
secondary hypothyroidism and monitoring of TSH-suppression therapy.
Home |
General
Information
| Billing
| Contact Us