thyroid disease Flashcards
thyroid gland
- small saddle shaped gland that wraps around the anterior portion of the trachea
- altered porduction of the thyroid hormones affects all major organ systems
- thyroid disorders are among the most common endocrine disorders and if left untreated, can result in cardiac disease and ultimately death
diagnostic tests
- thyroid antibodies (TA) thyroid
- TSH test (sensitive assay)
- T4 test
- T3 test
- T3 uptake test
- RAI uptake test (thyroid scan)
- thyroid suppression test
TA test
- serum TA is measured to determine whether a thyroid autoimmune disease is causing the client’s symptoms
- TA is elevated in Grave’s disease
TSH test
- serum TSH levels are measured and compared with T4 levels to differentiate pituitray from thyroid dysfunction.
- the best indicator of primary hyperthyroidism is suppression of TSH below 0.1 mcg/mL
- when the sensitive TSH is not suppressed the hyperthyroidis is caused by a TSH secreting pituitary tumor
T4 test
- serum T4 leves are measured to determine TH concentration to test thyroid gland function.
- T4 levels are elevated in hyperthyroidism ad acute thyroiditis
T3 test
- serum is measured by radioimmunoassay which measures bound and free forms of this hormone
- this test is effective for the diagnosis of hyperthyroidism
- T3 levels also may be elevated in thyroiditis
T3 uptake test
-T3 uptake is measured by an invitro test in which the pts blood is mixed with radioactive T3, the results are elevated in hyperthyroidism
RAI uptake scan
- measures the absorption of 131-I or 123-I by the hyroid gland
- a calculated dose of RAI is given orally or IV, an the thyroid is scanned often after 24 hrs. the distribution of radioactivity in the gland is recorded
- -RAI increase uptake is seen with Grave’s disease
- in addition the scan reveals the size and shape of the gland
thyroid suppression test
- RAI and T4 levels are measured first, the pt takes thyroid hormone for 7-10 days, after which the tests are repeated
- failure of the hormone therapy to suppress RAI and T4 indicate hyperthyroidism
The two primary lab findings used to confirm the diagnosis of hyperthyroidism are
- decreased TSH and elevated free thyroxine free T3 levels
- total T3 and T4 levels may also be assessed but they are not as definitive
serum TA test
- normal value: negative to 1:20
hyperthyroidism: increased
hypothyroidism: normal
serum TSH test (sensitive assay)
normal: 0.35-5.5 mU/mL
hyperthyroidism: decreased (in primary)
hypothyroidism: increased in primary
serum T4
normal: 4.5-11.5 mcg/dL
hyperthyroidism: increased
hypothyroidism: decreased
serum T3
normal: 80-200
hyperthyroidism: increased
hypothyroidism: decreased
T3 uptake
normal: 25-35 relative percentage
hyperthyroidism: increased
hypothyroidism: decreased
thyroid suppression
hyperthyroidism: increased RAI uptake to T4 levels
hypothyroidism: no change in RAI uptake or T4 levels