Investigation of Grave’s Disease

Laboratory Tests
BLOOD TESTS Thyroid Function Test

1. Ultrasensitive TSH test
a. Detects even tiny amounts of TSH in the blood
b. High TSH indicates thyroid gland is failing because ofproblem that is directly affecting throud (Primary hypothyroidism)
c. Low TSH indicares overactive thyroid that producing too much thyroid (Hyperthyroidism)
d. Low TSH: abnormal pituitary gland that prevents it from making enough TSH to stimulate thyroid (secondary hypothyroidism)


2. T4/throxine test [Free T4 (Ft4) or Free T4 Index (FT4I or FTI)]
a. Circulates in the blood in 2 forms: bound to proteins that prevent the T4 from entering tissues/ free T4 that enter tissues freely
b. Free T4 fraction determine how the thyroid is functioning
c. High FT4/FTI  hyperthyroidism; low  hypothyroidism
d. elevated TSH and low FT4 or FTI indicates primary hypothyroidism due to disease in the thyroid gland.
e. A low TSH and low FT4 or FTI indicates hypothyroidism due to a problem involving the pituitary gland.
f. A low TSH with an elevated FT4 or FTI is found in individuals who have hyperthyroidism.


3. T3/triiodothyronine test
a. to diagnosis hyperthyroidism or to determine the severity of the hyperthyroidism.
b. High T3 = hyperthyroid
 
4. Thyroid-stimulating immunoglobulin test (TSH antibody test)
a. Isn’t necessary to diagnose Grave’s
b. Most people with Grave’s have this antibody, but people with other hyperthyroidism do not.
c. 2 antibodies: throid peroxidase and thyroglobulin
d. Anti_thyroid peroxidase (anti-TPO): Autoantibody that found in most people with Grave’s disease, as well as in Hashimptp’s thyroiditis.


Imaging Tests
1. The radioactive iodine uptake test (RAIU)
o Thyroid gland uses iodine to make thyroid hormone (T4)
o Measures the amount of iodine the thyroid collects from the bloodstream. High levels of iodine uptake can indicate hyperthyroidism, eg. Graves’ disease.
o A thyroid scan shows how and where iodine is distributed in the thyroid. In Graves’ disease, the entire thyroid gland is involved so the iodine shows up throughout the gland. Other causes of hyperthyroidism such as nodules—small lumps in the gland—will show a different pattern of iodine distribution.

2. Ultrasond with color-Doppler evaluation
o Cost effective
o 1st step in all hyperthyroid patients

References:
http://www.endocrine.niddk.nih.gov/pubs/graves/
http://www.thyroid.org/patients/brochures/Graves_brochure.pdf
http://www.labtestsonline.org/understanding/conditions/graves-2.html
http://emedicine.medscape.com/article/120619-diagnosis
http://www.thyroid.org/patients/brochures/FunctionTests_brochure.pdf