thyroid function tests ppt
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Dr. Vijay Marakala, MBBS, MD.Senior LecturerBIOCHEMISTRY
IMS, MSU.
THYROID FUNCTION TESTS
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THYROID FUNCTION TESTS
Introduction Indications Assay of Hormones
Radio Iodine Uptake
Detection of Thyroid
Antibodies
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THYROID FUNCTION TESTS
THE THYROID GLAND IS A BUTTERFLY-
SHAPED ENDOCRINE GLAND THAT IS
NORMALLY LOCATED IN THE LOWER
FRONT OF THE NECK
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THYROID FUNCTION TESTS
Laboratory determinations of thyroid function are useful in distinguishing patients with euthyroidism (normal
thyroid gland function) from those with hyperthyroidism (increased function) or hypothyroidism (decreased
function)
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DISEASES OF THYROID GLAND
Hypothyroidism Hyperthyroidism
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SIGNS AND SYMPTOMS OF HYP0THYROIDISM
Cold intolerance, Bradycardia
Depression
Fatigue, Goiter Hyperlipidemi
a
Weight gain
Dry skin and dry hair,
Myxedema
Menstrual irregularities
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SIGNS AND SYMPTOMS OF HYPERTHYROIDISM
Heat intolerance
Fine resting tremor
Tachycardia Palpitations
Anxiety Sleep
disturbance
Irritability
Fatigue
Menstrual irregularitie
s
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THYROID FUNCTION TESTS-INDICATIONS
Suspicion of thyroid disease based on clinical signs and
symptomsScreening for
thyroid disease
Evaluation of treatment for thyroid
disease.
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BLOOD TESTS TO EVALUATE THYROID FUNCTION
Thyroid-stimulating hormoneTSH
Serum total thyroxineT4
Serum total triiodothyronineT3
Free thyroxineFT4
Free T3FT3
Antithyroid peroxidase antibodies, Antithyroglobulin antibodiesThyroid
antibodies
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TSH : THYROID-STIMULATING HORMONE
Elevated TSH (>5 mU/L
hypothyroidism Low TSH (<0.5 mU/Lhyperthyroidism
Normal range: 0.5 – 5mU/L
One of the best thyroid function screening test
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T4:SERUM TOTAL THYROXINE
Hypothyroidism• Decreased T4
Hyperthyroidism• Increased T4
Normal range: 65 – 150nmol/L
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T3: SERUM TOTAL TRIIODOTHYRONINE
Hypothyroidism• Decreased T3
Hyperthyroidism• Increased T3
Normal range: 1.8 – 3nmol/L
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FT4: FREE THYROXINE
Is the metabolically active thyroid hormone–not bound to protein
Should be ordered when TSH is abnormal to determine thyroid hyperfunction or
hypofunction
Normal range: 10 - 23 pmol/L
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FT3: FREE TRIIODOTHYRONINE
In nonthyroidal illness, a low FT3 level is a nonspecific finding.
FT3 is done to rule out T3 toxicosis
Normal Adults: 4.0–7.4 pmol/L
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FREE THYROXINE INDEX (FTI) The free thyroxine index (FTI) is a mathematical calculation
used to correct the estimated total T 4 for the amount of TBG present.
Make a calculation based on results of T 3 uptake and T 4 total, as follows: FTI= Total T4XT3 UPTAKE(%)/100
Normal Adults: 1.5–4.5 index
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METHODS USED TO MEASURE THYROID HORMONES
• RadioimmunoassayRIA• Enzyme-linked immunosorbant
assayELISA• Chemiluminescent immunoassayCLIA• Fluorescent immunoassayFIA
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THYROID ANTIBODIES
Antithyroid peroxidase antibodies
Used to diagnose suspected Hashimoto’s thyroiditis in
hypothyroidism
Antithyroglobulin antibodies
Used to diagnose autoimmune thyroiditis or Graves’ disease in
hyperthyroidism
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TRH RESPONSE TESTTRH RESPONSE TEST
TRH administration stimulate production of TSH
If hypothalamo-pituitary-thyroid axis is normal, T3 and T4 secretions will be increased
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TRH RESPONSE TESTIn primary
hyperthyroidism
• little or no change in TSH levels
In primary hypothyroidism
• Prompt
increase in TSH
In secondary hypothyroidism• Does not
produce an increase in TSH
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RADIOACTIVE IODINE UPTAKE131I used to detect
functional derangements of
thyroid gland.About 15 mci of 131I given intravenousl
y After a few hours, the patient is monitored at the
neck region by movable gamma-ray counter, which will pick up the radiation emitted by thyroid
gland
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RADIOACTIVE IODINE UPTAKE
Normal response• About 25% uptake by
thyroid within 2 hours• About 50% uptake by
thyroid within 24 hours
Abnormal response• Increased uptake in
hyperthyroidism• Decreased uptake in
hyporthyroidism
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