investig

investig

• 1.
  Investigation of hyperthyroidism andhypothyroidism NAIF TAMI ALSHAMMARI 331100190
• 2.
  Thyroid function tests -Specimen collection : • Specimens are routinely collected in a clot tube, although anticoagulants can be used . • Specimens free of lipemia or hemolysis are preferred .
• 4.
  The tests usedto investigate thyroid function can be grouped into: • Tests that establish whether there is thyroid dysfunction ( TSH,T4 and T3 measurements) • Tests to know the cause of thyroid dysfunction (thyroid auto-antibody and serum hyroglobulin measurements, thyroid enzyme activities, biopsy of the thyroid, ultrasound and isotopic thyroid scanning )
• 5.
  TSH : - Thesingle most sensitive, specific and reliable test of thyroid status . - In primary hypothyroidism [TSH] is increased. - In primary hyperthyroidism, [TSH] is decrease .
• 6.
  Total T4 andTotal T3 :  More than 99% of T4 and T3 circulate in plasma bound to protein .  -Both [total T4] and [total T3] change if [TBG] alters e.g. in pregnancy .
• 7.
  :Free T4 andFree T3 Free thyroid hormone concentrations are independent of changes in the concentration of thyroid-hormone binding proteins → more reliable for diagnosis of thyroid dysfunction.
• 8.
  Interpreting results ofthyroid function tests: :Primary hyperthyroidism - Plasma [TSH] : ↓ due to feedback inhibition on the pituitary -- Plasma free and total T4 and T3 concentrations : ↑In a very small percentage of hyperthyroid patients, plasma [total T4] and [freeT4] are both normal, whereas both plasma [total T3] and [freeT3] are increased ; this condition is known as T3 hyperthyroidism or T3 thyrotoxicosis .
• 9.
  Primary hypothyroidism : Plasma[TSH] : ↑ Plasma [free T4] and [total T4] : ↓ Plasma free T3 and total T3 measurements are of no value here, since normal concentrations are often observed .
• 10.
  Plasma [TSH] :abnormal Thyroid hormone levels : normal [TSH] : low → sub clinical hyperthyroidism [TSH] : elevated → sub clinical hypothyroidism Before the diagnosis of sub clinical thyroid disease can be made, causes of an abnormal plasma [TSH] other than thyroid disease must be excluded eg : - pregnancy - drug treatment Sub clinical primary thyroid disease :
• 11.
  :Secondary thyroid disorders Central (pituitary) hypothyroidism : [TSH] & thyroid hormone levels → low  Hyperthyroidism due to a TSH-secreting tumor very rarely
• 12.
  MY REFRENCE :Medlinepluse