Transcript thyroid gland


 The thyroid gland
The thyroid gland is a small butterfly-shaped gland at the
base of the neck. It weighs only about 20 grams. However,
the hormones it secretes are essential to all growth and
metabolism. The gland is a regulator of all body
functions. Thyroid disorders are found in 0.8-5% of the
population and are 4 to 7 times more common in women.
 Types of thyroid disease
There are many types of thyroid disease. However, the
main conditions present in most thyroid illnesses are
hypothyroidism (thyroid under activity) and
hyperthyroidism (thyroid over activity).
The amino acid tyrosine is the
starting point in the synthesis

Thyroid hormones release
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The following are commonly used
thyroid tests
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1. Radioactive iodine tests, testing uptake by the
thyroid gland
2. Hormones concentration T3,T4
3. Thyroid Binding Globulin
4. Concentration of TSH
5. Urinary excretion of thyroid hormones
6. Tests influenced by the actions of thyroid
hormones.(glucose tolerance test, calcium,
cholestrol)
7. Thyroid antibody tests for cases autoimmune.
Tests for evaluate
thyroid gland

 The main contribution of chemical measurements to
the investigation of thyroid disease is to help subdivide patients into the categories of effects of
treatment.
Thyroid hormones
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 It must be emphasized that a single thyroid function
test is not absolute in diagnostic accuracy and thus, a
careful selection of tests, so that their combination
can give comprehensive data, would enhance the
diagnostic accuracy.
Sample collection
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 Type of sample: blood, urine
 Most blood tests involving hormones measure the
bound protein. However, saliva-based testing
measures the free level of hormone.
 Conditions for test: you should ask the patient if
he/she under treatment and receive drug or made
surgery thyroidectomy recently.
 Preparation the patient: be kind when you deal with
patient.
 You should read the diagnosis status on request.
TSH
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 Concentrations are usually lowered in thyroxicosis,
due feedback inhibition of hypothalamus and
pituitary
 Conversely, plasma TSH is increased in
hypothyroidism, except for the rare cases of
hypothyroidism secondary to pituitary disease.
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TSH is the most appropriate test when monitoring
patients receiving thyroxine for the treatment of
hypothyroidism.
It should be measured no sooner than 6-8 weeks after
the start of treatment.
In the unusual situation where thyroid function needs
to be assessed before this time, FT4 should be
used, as the TSH will not have plateaued at this
stage.
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TSH - In most situations TSH analysed using a high sensitivity
assay is now accepted as the first line test for assessment of
thyroid function. A TSH between 0.4 and 4.0 mIU/L gives 99%
exclusion of hypo- or hyperthyroidism,12 while the TSH is
considered more sensitive than FT4 to alterations of thyroid
status in patients with primary thyroid disease.
Thyroglobulin – Levels are increased in all types of thyrotoxicosis,
except thyrotoxicosis factita caused by self-administration of
thyroid hormone. The main role for thyroglobulin is in the
follow-up of thyroid cancer patients.
After total
thyroidectomy and radioablation, thyroglobulin levels should
be undetectable; measurable levels (>1 to 2ng/mL) suggest
incomplete ablation or recurrent cancer.
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 Thyrotropin (TSH)-secreting adenomas These rare
tumors make too much thyroid-stimulating hormone
(TSH), which then causes the thyroid gland to make
too much thyroid hormone. This can cause
symptoms of hyperthyroidism (overactive thyroid),
T3
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 Is more biologically active than T4 but both
hormones have similar actions in the body.
 T3 is not usually used in confirming the diagnosis of
suspected hypothyroidism because other tests can
demonstrate hypofunction of the thyroid gland.
 Sometimes, however, a client may have clinical
signs of thyrotoxicosis with a normal T4.
Measurement of the T3 is then needed, because T3
may be elevated in thyrotoxicosis while other
thyroid tests are still the normal range.
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 FT3 - FT3 has little specificity or sensitivity for
diagnosing hypothyroidism and adds little diagnostic
information. The main value of FT3 is in the
evaluation of the 2 to 5% of patients who are
clinically hyperthyroid, but have normal FT4. In
this situation, an elevated FT3 would be suggestive
of T3 toxicosis, in which the thyroid secretes
increased amount of T3 or there is excessive
conversion of T4 to T3.
T4
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 The interpretation of results for serum T4 needs to take
into account alterations in the thyroid-binding proteins.
 The free thyroxine index (FTI) is determined by the
following calculation:
 FTI = Thyroxine (T4)/Thyroid Binding Capacity
 The FTI is a normalized determination that remains
relatively constant in healthy individuals and
compensates for abnormal levels of binding proteins.
 Hyperthyroidism causes increased FTI and
hypothyroidism causes decreased value.
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 FT4 - This test measures the metabolically active,
unbound portion of T4. Measurement of FT4
eliminates the majority of protein binding errors
associated with measurement of the outdated total
T4, in particular the effects of oestrogen.
Reference range
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FreeT4
ng\dl
{.8 – 2.2}
TotalT4
Ug\ml
{4.5 – 12.5}
Free T3
Pg\ml
{1.95- 5.85}
Total T3
ng\ml
{.6 – 1.85}
TSH
MlU\ml
{.5-5 }
Parathyroid
hormone(PTH)
Pg\ml
{9-52}
Clinical interpretation

There are marked variations in the thyroid function
with age, evident in all of the vitro hormone and
proteins measurements.
In general thyroid function parameters in healthy
subjects show little or no clinical significant gender or
racial variation.
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Clinically errors
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 Quality control, the best step for all analytical tests to
have a reliable result and a voiding the errors.
 Pre analytical
 Analytical process
 Post analytical process
Case study
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 A 63-year-old woman has Hashimoto’s disease. Her
thyroid laboratory values today include the
following: She feels consistently run down and has
dry skin that does not respond to the use of hand
creams.
The hormones levels:
 TSH 10.6 mIU/L (normal (0.5–4.5 mIU/L)
 A free T4 concentration of 0.5 ng/dL (normal 0.8–1.9
ng/dL).