NBME Free 120 Branch of the thyrocervical trunk (NBME Answers)

Retired NBME Free 120 Answers

free120/Block 2/Question#13 (reveal difficulty score)
A 33-year-old man undergoes a radical ...
Branch of the thyrocervical trunk 🔍 / 📺 / 🌳 / 📖
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submitted by ∗sphazhang(1)

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does anyone understand why the parathyroid hormone concentration is so high when this is supposed to be an iatrogenic hypoparathyroidism question? this really threw me off

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drdoom Inadvertent and abrupt ligation of an artery kills the blood supply to tissue (ISCHEMIA). The tissue (parathyroid gland) will begin to undergo necrosis, releasing its contents, which, in this case, includes a boatload of PTH. +4

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submitted by mdmofongo(0)

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The inferior thyroid artery (branch of the thyrocervical trunk) irrigates the posterior thyroid, including the parathyroid hormones.

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submitted by ∗dpineda28(0)

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The vignette describes a patient with hypoparathyroidism, likely due to damage to the parathyroid blood supply during thyroidectomy.

The parathyroids are supplied primarily by the inferior thyroid arteries, which branch from the thyrocervical trunk.

Collaterals from the superior thyroid arteries (branches of the external carotids) exist but are supplementary.

Reference: https://www.ncbi.nlm.nih.gov/books/NBK537203/

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submitted by ∗bwdc(697)

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This question is asking for the vascular supply of the parathyroid glands. That would be the inferior thyroid arteries, which arise from the thyrocervical trunk.

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brendan why wouldn’t a branch of the external carotid also be a valid answer? does the superior thyroid not also give arterial supply to the parathyroid glands? it seems to me that it could be either of these. +2

bwdc @brendan Superior thyroid provides mostly collateral support. The inferior thyroid is the primary supply and thus the “single best answer.” Remember, the other choices don’t have to be WRONG—they’re just not the best. +

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submitted by ∗b1ackcoffee(115)

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Calcium is low while PTH is high. It’s primary hyperparathyroidism (not secondary). Ans is branch of IJV.

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mdmofongo You’re right, how weird. But I guess following the Hx there is no other way to approach it? Not a fair question I would agree. Also the inferior thyroid artery does branch off of the thyrocervical trunk. The superior and middle veins of the thyroids drain into the IJV. +

b1ackcoffee I got that it must be some vein, I just didn’t know the tributaries. Oh well, anatomy fucks me again! +

azibird I believe this would be more likely called a type of pseudohypoparathyroidism. Akin to PTH resistance, the PTH just can't get out to do its thing. Good catch though, I didn't even get what was happening here. +

azibird From wikipedia: "Each parathyroid vein drains into the superior, middle and inferior thyroid veins. The superior and middle thyroid veins drain into the internal jugular vein, and the inferior thyroid vein drains into the brachiocephalic vein." https://en.wikipedia.org/wiki/Parathyroid_gland +

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