Block 5 Endo Thyroid Gland MCQ's

Levothyroxine is the most appropriate drug for replacement therapy in a hypothyroid patient. Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. Levothyroxine is a synthetic form of the thyroid hormone thyroxine, which helps to restore the levels of thyroid hormones in the body. It is the standard treatment for hypothyroidism and is effective in relieving the symptoms associated with the condition. Other options like Propranolol, Triiodothyronine, Propylthiouracil, and Lithium are not suitable for replacement therapy in hypothyroid patients.

Hashimoto's thyroiditis is an autoimmune disease where the body's immune system mistakenly attacks the thyroid gland. This leads to inflammation and damage to the thyroid tissue, causing it to become underactive. The term "autoimmune destruction" accurately describes the cause of Hashimoto's thyroiditis, as it highlights the fact that the immune system is responsible for attacking and destroying the thyroid gland in this condition.

In cases of iodine deficiency, the thyroid gland is unable to produce enough thyroid hormones, leading to hypothyroidism. T4 (thyroxine) is the main hormone produced by the thyroid gland, and its levels are reduced in hypothyroidism. TSH (thyroid-stimulating hormone) is released by the pituitary gland to stimulate the thyroid gland to produce thyroid hormones. In response to low levels of thyroid hormones, TSH levels are elevated in hypothyroidism as the pituitary gland tries to stimulate the thyroid gland to produce more hormones. Therefore, in cases of iodine deficiency, the expected results would be T4 reduced and TSH elevated.

In a patient with a benign thyroid adenoma ("toxic nodule"), the adenoma produces excessive amounts of thyroid hormone, leading to hyperthyroidism. This causes an elevation in T4 levels. However, since the adenoma is producing excessive thyroid hormone, the body's feedback mechanism tries to suppress the production of thyroid-stimulating hormone (TSH) from the pituitary gland. As a result, TSH levels are reduced. Therefore, in a patient with a benign thyroid adenoma, the expected results would be T4 elevated and TSH reduced.

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The patient's elevated TSH levels and presence of thyroid peroxidase antibodies indicate that she has hypothyroidism, specifically Hashimoto's thyroiditis. Levothyroxine is the appropriate drug for this patient as it is a synthetic form of thyroid hormone that can replace the deficient hormone and help regulate the patient's thyroid function. Potassium iodide is used for iodine deficiency, propranolol is a beta-blocker used for hypertension and heart conditions, methimazole is used for hyperthyroidism, loperamide is an anti-diarrheal agent, and diltiazem is a calcium channel blocker used for hypertension and angina.

Propylthiouracil is the correct answer because it is an anti-thyroid drug that inhibits the conversion of T4 to T3 by blocking the enzyme responsible for this conversion in the liver. This drug is commonly used in the treatment of hyperthyroidism to reduce the levels of thyroid hormones in the body. Levothyroxine is a synthetic form of T4 and does not block the conversion, while diiodotyrosine and TSH do not have any direct effect on the conversion process.

In Grave's disease, the enlargement of the thyroid gland is caused by an antibody that stimulates TSH receptors. This antibody, known as thyroid-stimulating immunoglobulin (TSI), binds to the TSH receptors on the thyroid gland and mimics the action of TSH. This leads to the overproduction of thyroid hormones, resulting in the enlargement of the thyroid gland. TSI is produced by the immune system and is believed to be the result of an autoimmune response, where the body mistakenly targets its own tissues.

The symptoms described in the question, such as large fontanelles, macroglossia, distended abdomen, and hypotonia, are consistent with congenital hypothyroidism. Levothyroxine is a synthetic form of thyroid hormone and is the treatment of choice for hypothyroidism. Methimazole is used to treat hyperthyroidism, somatrem is a growth hormone, theophylline is a bronchodilator, potassium iodide is used for iodine deficiency, and prednisone is a corticosteroid. Therefore, the most appropriate drug for this baby is levothyroxine.

The correct relationship between changes in plasma levels of T3 & T4 and release of TRH and TSH is that an increase in plasma levels of T3 & T4 leads to a decrease in the release of TRH and TSH. This is because T3 & T4 have negative feedback effects on the hypothalamus and pituitary gland, inhibiting the release of TRH and TSH.

After being treated with radioactive iodine, the woman's TSH levels are elevated. This suggests that her thyroid function is still low and she is experiencing hypothyroidism. The most likely drug prescribed at this point in time would be levothyroxine, which is a synthetic form of the thyroid hormone T4. Levothyroxine is commonly used to replace or supplement the body's own thyroid hormone production in cases of hypothyroidism.

Propylthiouracil is commonly used to treat hyperthyroidism, including Grave's disease. However, one serious toxicity that can occur, although rarely, is agranulocytosis. Agranulocytosis is a condition characterized by a severe decrease in the number of white blood cells, specifically neutrophils, which are important for fighting off infections. This can increase the risk of developing serious infections. It is important for patients taking propylthiouracil to be aware of this potential side effect and to seek medical attention if they experience symptoms such as fever, sore throat, or other signs of infection.

Thyroid peroxidase is an enzyme found in the thyroid gland that plays a crucial role in the synthesis of thyroid hormones. It catalyzes the coupling of two molecules of diiodotyrosine (DIT) to form thyroxine (T4). T4 is the main form of thyroid hormone produced by the thyroid gland and is later converted to the active form, triiodothyronine (T3), in peripheral tissues. This statement correctly describes the role of thyroid peroxidase in the synthesis of T4, making it the correct answer.

The patient's symptoms, such as tiredness, feeling cold, weight gain, and muscle cramps, along with the physical examination findings of dry skin and enlarged thyroid gland, suggest that she is experiencing hypothyroidism. The blood tests reveal elevated TSH levels and marginally below normal T3 and T4 levels, indicating primary hypothyroidism. The positive thyroid antibodies suggest that the patient has an autoimmune thyroid disease, most likely Hashimoto's thyroiditis. The administration of thyroxine, a synthetic form of the hormone T4, would be the appropriate treatment for this patient as it would help to replace the deficient thyroid hormone and alleviate her symptoms.

During pregnancy, the demand for thyroid hormone increases due to the growth and development of the fetus. Therefore, it is necessary to increase the dose of levothyroxine in pregnant women with hypothyroidism to maintain adequate thyroid hormone levels. This will ensure normal development of the fetus and help control the symptoms of hypothyroidism in the mother.

The correct answer is D. The mechanisms by which T3 increases cardiac output include increasing heart rate, increasing stroke volume, and enhancing myocardial contractility.

In this scenario, the patient's levels of both T3 and T4 are significantly lower than normal, while TSH is within the normal range. This suggests that the thyroid gland is functioning properly, but there may be an issue with the transportation or binding of T3 and T4 hormones in the blood. Thyroxin-binding globulin (TBG) is a protein that binds to T3 and T4 in the blood, allowing for their transport to target tissues. A deficiency in TBG would result in lower levels of bound T3 and T4, leading to the observed laboratory findings. Therefore, the most likely deficient protein in this patient is thyroxin-binding globulin in the blood.

Chronic iodine deficiency leads to decreased production of thyroid hormones, which results in elevated levels of thyroid-stimulating hormone (TSH) from the pituitary gland. TSH stimulates the thyroid gland to grow and produce more hormones, leading to the enlargement of the thyroid gland, known as goiter. Therefore, the elevated TSH level is most directly related to the enlargement of the thyroid gland in chronically iodine-deficient patients.

Thyroid follicles do not contain Para follicular cells, which are responsible for releasing calcitonin. Instead, these cells are found in the thyroid gland, but not within the follicles themselves. The other statements are true: thyroid follicles contain thyroglobulin, their lining is made up of epithelial cells that vary in appearance with gland activity, they are surrounded by a fenestrated capillary network, and they are stimulated by TSH.

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The correct answer is that thyroid follicular cells secrete T4 hormone. This is characteristic of the thyroid gland because the follicular cells are responsible for the production and secretion of thyroid hormones, including T4. T4, also known as thyroxine, is an important hormone involved in regulating metabolism and growth in the body.

THIS QUESTION DID NOT HAVE AN ANSWER "E", BUT THE ANSWER KEY SAYS THE ANSWER IS "E".