HY lecture notes:
Shelf and 2CK will want you to know how to manage thyroid nodules. Firstly, if the Q tells you a patient walks in and asks about thyroid cancer screening, and they ask you for the next best step, the wrong answer = TSH; the correct answer = “palpation of thyroid nodule.” Sounds incredibly vague and basic, but it’s the answer they want. You’re simply going to palpate / do a physical exam before you automatically order a TSH on someone.
After palpation detects a nodule, next step is ordering TSH. Our management is then determined by the TSH level.
Cancer is 99% of the time “cold,” meaning it’s hyposecretory and the patient will not be hyperthyroid. So in turn, the TSH of that patient should not be suppressed because T3 and T4 should be normal or low.
So if TSH normal or high, answer = do fine-needle aspiration (FNA) of the nodule to detect possible thyroid cancer. Ultrasound in isolation is always the wrong answer. Rarely you might see “ultrasound-guided FNA” or “ultrasound-guided biopsy,” but “ultrasound” alone is wrong. FNA is correct is correct.
If TSH is low, then the patient must be hyperthyroid because the T3 and T4 would be elevated, therefore suppressing it. Some students will read between the lines here and ask, “Well what about if TSH is low because of secondary hypothyroidism, such as due to pituitary insufficiency from Sheehan syndrome, or due to impingement secondary to prolactinoma?” And it’s true, TSH could be low in secondary hypothyroidism, but when the USMLE and shelf exams ask about thyroid nodule evaluation, they are referring to primary thyroid derangement (i.e., problems with the thyroid gland itself).
So if TSH is low, the nodule is likely “hot” and secreting thyroid hormone, so it’s not likely to be cancer. So rather than doing FNA, we do radioiodine uptake scan, which will often confirm the diagnosis of toxic adenoma (as opposed to common malignant variants such as papillary, follicular, medullary, and anaplastic thyroid cancer).
If the uptake scan shows multiple nodules rather than an isolated one, the diagnosis is toxic multinodular goiter, not toxic adenoma. Toxic multinodular goiter is the most common cause of hyperthyroidism in elderly. Yes, Graves occurs in elderly as well, but if you get a 79-year-old with hyperthyroidism, the Dx is likely TMG, whereas in a 29-year-old, it’s more likely to be Graves.
If the scan shows diffuse uptake, the Dx is Graves.
So in summary, for cancer screening:
1) Palpate thyroid gland.
2) If nodule palpated, order TSH.
3a) If TSH normal or high, order FNA. In this case the cold nodule may be cancer.
3b) If TSH low, order radioiodine uptake scan. In this case the hot nodule is unlikely to be cancer and more likely to be a simple toxic adenoma.
This concept is HY for surgery, FM, and IM shelves.
