Endocrinology Practice Questions

Correct Answer: B

Rationale: The correct answer is B: Inhibition of the function of thyroid peroxidase. Propylthiouracil inhibits thyroid peroxidase, an enzyme essential for thyroid hormone synthesis. By blocking this enzyme, propylthiouracil reduces the production of thyroid hormones, helping to manage hyperthyroidism in Graves' disease. Explanation: 1. Propylthiouracil directly inhibits thyroid peroxidase, unlike other antithyroid medications that target different mechanisms. 2. Inhibition of thyroid peroxidase leads to decreased synthesis of thyroid hormones, effectively controlling hyperthyroidism. 3. Other choices are incorrect because propylthiouracil does not primarily affect the production of thyroid-stimulating immunoglobulins (choice A), peripheral conversion of T4 to T3 (choice C), or iodine organification (choice D) in the treatment of Graves' disease. In summary, the inhibition of thyroid peroxidase by

Correct Answer: C

Rationale: Step-by-step rationale: 1. Tertiary hyperparathyroidism occurs due to prolonged secondary hyperparathyroidism in response to chronic renal failure. 2. In chronic renal failure, impaired kidney function leads to reduced activation of vitamin D and impaired calcium regulation. 3. Persistent hypocalcemia triggers the parathyroid glands to overproduce parathyroid hormone, leading to tertiary hyperparathyroidism. 4. Rickets (choice A) is associated with vitamin D deficiency, pseudohypoparathyroidism (choice B) is a genetic disorder, and malabsorption syndrome (choice D) affects nutrient absorption, but they are not commonly linked to tertiary hyperparathyroidism.

Correct Answer: D

Rationale: The correct answer is D because the anterior pituitary is regulated by hypothalamic neuropeptides. The hypothalamus secretes releasing and inhibiting hormones that control the anterior pituitary's hormone release. This close interaction between the hypothalamus and the anterior pituitary is known as the hypothalamic-pituitary axis. A is incorrect because the anterior pituitary is not neural tissue, it is an endocrine gland. B is incorrect because the anterior pituitary synthesizes and secretes peptide hormones, not steroid hormones. C is incorrect because the anterior pituitary is located at the base of the brain, not above the kidney.

Correct Answer: B

Rationale: Thyroid acropathy, also known as thyroid dermopathy, is a skin condition commonly associated with Graves' disease. This autoimmune disorder causes an overactive thyroid gland, leading to high levels of thyroid hormones in the blood. The excess thyroid hormones can trigger changes in the skin, resulting in thyroid acropathy. Subclinical hypothyroidism (choice A) is characterized by slightly elevated TSH levels with normal thyroid hormone levels, not typically associated with thyroid acropathy. Myxoedema (choice C) refers to severe hypothyroidism and is not linked to thyroid acropathy. Medullary carcinoma of the thyroid (choice D) is a type of thyroid cancer and is not known to cause thyroid acropathy. Therefore, the correct answer is B, Graves' disease, as it is the most common condition associated with thyroid acropathy.

Correct Answer: C

Rationale: The correct answer is C: Glucose-6-phosphatase deficiency. This enzyme is essential for gluconeogenesis and glycogenolysis, so its deficiency leads to fasting hypoglycemia. Galactosaemia (A) can cause hypoglycemia due to impaired galactose metabolism. Insulinoma (B) results in excess insulin production causing hypoglycemia. Systemic carnitine deficiency (D) can lead to hypoglycemia by impairing fatty acid oxidation, but it does not directly cause fasting hypoglycemia as seen in Glucose-6-phosphatase deficiency.