OUTLINE THE RELEVANT INVESTIGATIONS FOR HYPO AND HYPER THYROIDISM ( BLOOD…
OUTLINE THE RELEVANT INVESTIGATIONS FOR HYPO AND HYPER THYROIDISM ( BLOOD AND IMAGING)
When to suspect hypothyroidism?
depending on the severity and rapidity of onset
eg: Slow failure of thyroid function caused by autoimmune thyroiditis typically presents insidiously over years
1st step: Initial screening is by measuring the thyroid stimulating hormone (TSH) level.
Next: If this is elevated, the TSH should be repeated within 2–8 weeks with a free T4 level to confirm the diagnosis.
Nb: if there is a clinical picture for hypothyroidism, despite the absence of TSH elevation still do the test! WHY: to exclude the (much less common) possibility of central hypothyroidism due to pituitary or hypothalamic pathology.
If central hypothyroidism is suspected, the function of the hypothalamic-pituitary-adrenal axis should be tested and a magnetic resonance imaging (MRI) scan of the pituitary gland obtained
if there is associated secondary adrenal failure, thyroid hormone supplementation should only be commenced after glucocorticoid replacement, otherwise an adrenal crisis may be precipitated.
Thyroid autoantibodies (antithyroid peroxidase and antithyroglobulin antibodies) are positive in 95% of patients with autoimmune thyroiditis.
The thyroid peroxidase (TPO) antibody assay is sufficiently sensitive and specific to make this the only test now needed to confirm a diagnosis of autoimmune thyroiditis.
Do a neck examination; What to look for? the presence or absence of a goitre or thyroid nodules.
Do a systematic examination considering both aetiology (cause, set of causes, or manner of causation of a disease or condition.)
(eg. thyroidectomy scar, skin changes suggestive of previous external neck irradiation, specific autoimmune diseases such as vitiligo).
clinically unapparent disease with a large range of symptoms.
How to test for Hyperthyroidism?
Medical history and physical exam.
look for a slight tremor in your fingers when patient extends them, overactive reflexes, eye changes and warm, moist skin.
Examine your thyroid gland as you swallow to see if it's enlarged, bumpy or tender and check your pulse to see if it's rapid.
A diagnosis can be confirmed with blood tests that measure the levels of thyroxine and TSH in your blood.
High levels of thyroxine and low or nonexistent amounts of TSH indicate an overactive thyroid.
The amount of TSH is important because it's the hormone that signals your thyroid gland to produce more thyroxine. These tests are particularly necessary for older adults, who may not have classic symptoms of hyperthyroidism.
If blood tests indicate hyperthyroidism, some recommended follow up test may be used to help determine why your thyroid is overactive:
Radio iodine uptake test.
you take a small, oral dose of radioactive iodine (radioiodine). Over time, the iodine collects in your thyroid gland because your thyroid uses iodine to manufacture hormones
Check after two, six or 24 hours (sometimes after all) to determine how much iodine your thyroid gland has absorbed.
A high uptake of radioiodine indicates your thyroid gland is producing too much thyroxine. The most likely cause is either Graves' disease or hyperfunctioning nodules.
If you have hyperthyroidism and your radioiodine uptake is low, this indicates that the thyroxine stored in the gland is leaking into the bloodstream and indicates you may have thyroiditis.
A radioactive iodine uptake test isn't uncomfortable, but it does expose you to a small amount of radiation.
A radioactive isotope is injected into the vein on the inside of your elbow or sometimes into a vein in your hand.
then lie on a table with your head stretched backward while a special camera produces an image of your thyroid gland on a computer screen.
The time needed for the procedure may vary, depending on how long it takes the isotope to reach your thyroid gland.
Sometimes you may have a thyroid scan as part of a radioactive iodine uptake test. In that case, the orally administered radioactive iodine is used to image your thyroid gland.
may have neck discomfort and be exposed to a small amount of radiation.