Endocrinology Practice Questions

Correct Answer: C

Rationale: The correct answer is C because dipsogenic diabetes insipidus is caused by a defect or damage to the hypothalamus, not the pituitary gland or pituitary stalk. The hypothalamus regulates thirst and water intake, so damage to this area can lead to excessive thirst and dilute urine output characteristic of diabetes insipidus. Choices A and D incorrectly attribute the cause to the pituitary gland or pituitary stalk, which are not directly involved in regulating thirst. Choice B is incorrect as it mentions malfunction of the hunger mechanism, which is not relevant to dipsogenic diabetes insipidus. Thus, choice C is the most accurate definition based on the pathophysiology of the condition.

Correct Answer: B

Rationale: The correct answer is B: Cortisol. The adrenal cortex produces cortisol, a steroid hormone involved in stress response and metabolism. Norepinephrine (A) is produced by the adrenal medulla. 5-DHEA (C) is a precursor to sex hormones and not directly produced by the adrenal cortex. Aldosterone (D) is produced by the adrenal cortex but is involved in regulating salt and water balance, not directly related to cortisol production.

Correct Answer: C

Rationale: The correct answer is C: Purple skin striae. This is the most common sign of Cushing's syndrome due to the excessive production of cortisol leading to thinning of the skin and formation of purple stretch marks. Hirsutism (A) is excessive hair growth, not specific to Cushing's. Obesity (B) can be a symptom, but it is not the most common. Skin hyperpigmentation (D) is seen in Addison's disease, not Cushing's.

Correct Answer: A

Rationale: The correct answer is A: Acute pancreatitis. Hyperparathyroidism is not typically associated with acute pancreatitis. Hyperparathyroidism is characterized by excessive production of parathyroid hormone, leading to increased calcium levels in the blood. Nephrocalcinosis, palpable neck swelling, and pseudogout are commonly seen in hyperparathyroidism due to the effects of elevated calcium levels on the kidneys, parathyroid glands, and joints, respectively. Acute pancreatitis, on the other hand, is more commonly associated with gallstones, alcohol consumption, or certain medications, rather than hyperparathyroidism.

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