The primary action of antithyroid drugs is to:
Increase thyroid hormone production.
Decrease thyroid hormone synthesis.
Stimulate TSH release.
Destroy thyroid tissue directly.
The Correct Answer is B
Choice A rationale
Antithyroid drugs are used to treat hyperthyroidism, a condition characterized by excessive thyroid hormone production. Their primary mechanism is to decrease, not increase, the synthesis of thyroid hormones to bring the body's metabolic rate back to a normal range.
Choice B rationale
The primary action of antithyroid medications, such as methimazole and propylthiouracil, is to inhibit the synthesis of thyroid hormones within the thyroid gland. They achieve this by blocking key enzymatic steps involved in the production of triiodothyronine ($T_3$) and thyroxine ($T_4$).
Choice C rationale
Antithyroid drugs do not directly stimulate the release of thyroid-stimulating hormone (TSH). TSH is produced by the pituitary gland, and its release is primarily regulated by the hypothalamus's secretion of thyrotropin-releasing hormone (TRH) and a negative feedback loop from circulating thyroid hormones.
Choice D rationale
While some antithyroid treatments, like radioactive iodine, do destroy thyroid tissue, this is not the primary action of most antithyroid drugs such as methimazole and propylthiouracil. These drugs work by inhibiting hormone production, leaving the thyroid tissue itself intact.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["A","C","D"]
Explanation
Choice A rationale
Propylthiouracil (PTU) is an antithyroid drug that works by inhibiting the enzyme thyroid peroxidase, which is responsible for the organification and coupling steps of thyroid hormone synthesis. This action reduces the production of new thyroid hormones, making it effective in treating hyperthyroidism.
Choice B rationale
Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism. It does not inhibit thyroid hormone production and is not an antithyroid medication; rather, it replaces deficient thyroid hormone, acting in direct opposition to antithyroid drugs.
Choice C rationale
Radioactive iodine is an antithyroid medication used to treat hyperthyroidism. When ingested, it is selectively absorbed by the thyroid gland, where its radiation destroys a portion of the thyroid tissue, thereby reducing the production of thyroid hormones.
Choice D rationale
Methimazole is a thionamide antithyroid drug that inhibits thyroid hormone synthesis by blocking the oxidation of iodide and the coupling of iodotyrosine residues, similar to PTU. It is a common and effective treatment for hyperthyroidism.
Correct Answer is B
Explanation
Choice A rationale
Metformin is a biguanide that works by decreasing hepatic glucose production and improving insulin sensitivity in peripheral tissues. It does not stimulate insulin release from the pancreas; rather, it makes the body's existing insulin more effective.
Choice B rationale
Glyburide is a sulfonylurea oral hypoglycemic agent. Its primary mechanism of action is to stimulate the beta cells of the pancreas to release more insulin. This makes it effective in lowering blood glucose levels, but also carries a risk of hypoglycemia.
Choice C rationale
Pioglitazone is a thiazolidinedione (TZD) that acts on peroxisome proliferator-activated receptor gamma (PPAR-γ) to increase insulin sensitivity in muscle and adipose tissue. It does not stimulate the release of insulin but rather addresses insulin resistance.
Choice D rationale
Acarbose is an alpha-glucosidase inhibitor. It works in the intestine to delay the digestion of carbohydrates. This slows down glucose absorption after a meal, reducing the postprandial blood glucose spike. It does not affect insulin secretion.
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