Let's revise the primary and
secondary hyperthyroidism syndromes.
Graves' disease will give you the classic
appearance of low TSH, high T4 and/or high T3.
Key testing that will help differentiate it is the
presence of thyroid stimulating immunoglobulins
and a diffuse uptake on
radioactive iodine scan.
The next condition is toxic
Here the pattern of thyroid test is very similar to
Graves' disease but you can differentiate it clinically
but also based on the appearance of
radioactive iodine uptake scanning
where one see would multiple
nodules with increased uptake.
In the case of a toxic adenoma, again, thyroid
hormone evalualtion of the serum will be similar
but radioactive iodine scanning will
reveal a single area of increased uptake
over the single toxic adenoma.
In subacute thyroiditis again, TSH
is low, free T4 and T3 are elevated
but radioactive iodine scan shows lows
uptake, usually less that 10%.
And you may also have a negative TPO antibody to
differentiate it from Hashimoto's thyroiditis.
And then finally, the rare condition of secondary
hyperthyroidism usually caused by TSH-secreting adenoma.
Your TSH here will be normal or high in
conjunction with elevated T4 and T3.
Here, radioactive iodine
scanning is unhelpful
and an MRI of the brain is usually
required to evaluate for a pituitary mass.
Let's talk about subclinical
Here, TSH is low with normal T4 and T3.
Patients are mostly asymptomatic or
in some cases mildly thyrotoxic.
Repeat assessment of thyroid function
6-12 weeks after diagnosis is required.
Values tend to normalize in thirty
percent of patients without any action.
Treatment only takes place when the thyroid stimulating
hormone level is less than 0.1 milliunit per liter.