A nuclear waste disposal plant suffers a containment failure and several grams of iodine-131 are released into the local environment. A number of workers are believed to have been exposed to dangerous levels of the radioactive material. Which of the following should be immediately administered to help prevent tissue damage in these individuals?

Question

A nuclear waste disposal plant suffers a containment failure and several grams of iodine-131 are released into the local environment.  A number of workers are believed to have been exposed to dangerous levels of the radioactive material.  Which of the following should be immediately administered to help prevent tissue damage in these individuals?

Quizplus · Accepted Answer

11ec160b_3bc5_2664_9249_6b00a0166b44_MD0001_00 Radioactive material such as iodine-131 (¹³¹I) can be released into the environment following nuclear reactor accidents, breach-of-containment at waste disposal sites, or atomic bomb blasts. Like non-radioactive iodine, ¹³¹I is preferentially taken up and concentrated within the thyroid gland. There it can cause significant tissue damage that may result in radiation-induced hypothyroidism and thyroid carcinoma (particularly in younger patients). In the event of a nuclear accident, potassium iodide is given prophylactically to protect the thyroid from excessive accumulation of radioactive ¹³¹I. Energy-dependent transport of inorganic iodide into the thyroid follicular cell (iodide trapping) is accomplished by the sodium-iodide symporter located on the basolateral membrane. Because this transporter takes up all isotopes of iodide (as well as other ions such as perchlorate and pertechnetate), high serum levels of nonradioactive iodide can competitively inhibit radioactive I¹³¹ from entering thyroid follicular cells. Large increases in serum iodide levels also inhibit iodine organification (Wolff-Chaikoff effect) and reduce thyroid hormone release. (Choice A) Levothyroxine is a synthetic form of T4 used to treat hypothyroidism. High doses of levothyroxine suppress TSH, just as high amounts of natural T4 would. Because TSH stimulates iodine trapping, high doses of levothyroxine would ultimately reduce iodine uptake in the thyroid follicular cells. However, this regulatory process requires several days to weeks to take effect. (Choices C and D) Propranolol is used to reduce the adrenergic effects of thyrotoxicosis (eg, tachycardia, tremor). Prednisone is used to reduce lymphocyte-mediated inflammatory effects in Graves ophthalmopathy. However, neither propranolol nor prednisone affects the uptake of iodine in thyroid follicular cells. (Choice E) Propylthiouracil is used in the treatment of hyperthyroidism and decreases formation of thyroid hormone by inhibiting the enzyme thyroid peroxidase. Although inhibition of iodine organification will cause decreased iodide uptake by the thyroid, potassium iodide promotes this effect more rapidly and efficiently by also acting as a competitive inhibitor for iodide entry into the cell. Educational objective: Potassium iodide competitively inhibits thyroid uptake of radioactive iodine isotopes and is often administered following nuclear accidents to protect the thyroid and prevent development of radiation-induced thyroid carcinoma. __________ References: Potassium iodide (KI) to block the thyroid from exposure to I-131: current questions and answers to be discussed. (http://www.ncbi.nlm.nih.gov/pubmed/23475155)

A Nuclear Waste Disposal Plant Suffers a Containment Failure and Several