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: A

Rationale: Aldosterone increases potassium excretion by promoting the reabsorption of sodium and water in the kidneys, leading to potassium excretion. This helps maintain electrolyte balance. Other choices are incorrect because aldosterone does not directly increase water loss, is released in response to low blood volume, and is deficient in Addison's disease.

Correct Answer: A

Rationale: The correct answer is A: Phaeochromocytoma. Multiple Endocrine Neoplasia Type I (MEN I) is characterized by tumors in the pituitary, pancreas, and parathyroid glands. Phaeochromocytoma is not typically associated with MEN I. Phaeochromocytoma is commonly seen in MEN II syndrome. Therefore, A is the correct answer. Choice B, C, and D are incorrect as they are all associated with MEN I based on the characteristic tumor involvement in the pituitary, pancreas, and parathyroid glands, respectively.

Correct Answer: C

Rationale: The correct answer is C: Stress. Stress triggers the release of growth hormone through the activation of the hypothalamic-pituitary-adrenal axis. When the body is under stress, the hypothalamus signals the pituitary gland to release growth hormone. This hormone then stimulates growth and cell reproduction. Glucocorticoids (A) and somatostatin (B) actually inhibit the release of growth hormone. Obesity (D) can lead to decreased growth hormone release due to disrupted hormonal regulation. In summary, stress is the correct answer as it directly stimulates the release of growth hormone, while the other choices inhibit or have a negative impact on growth hormone release.

Correct Answer: B

Rationale: Excess prolactin causes gynaecomastia due to its stimulatory effect on breast tissue growth in males. Prolactin inhibits the release of testosterone, leading to an imbalance in sex hormones and breast tissue development. Acromegaly is caused by excess growth hormone, not prolactin. Early menopause is unrelated to prolactin levels. Anaemia is typically not associated with prolactin excess. Thus, gynaecomastia is the most appropriate outcome of excess prolactin.