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: A

Rationale: Rationale: A: Correct. Cushing's disease is caused by a pituitary adenoma secreting excess ACTH, stimulating adrenal cortex to produce excess cortisol. B: Incorrect. Cushing's disease does not result from excess cortisol secretion by the pituitary adenoma. C: Incorrect. Cushing's disease is not caused by an adrenal adenoma secreting excess ACTH. D: Incorrect. Cushing's disease is not caused by an adrenal adenoma secreting excess cortisol. Summary: The correct answer is A because it accurately describes the pathophysiology of Cushing's disease, where a pituitary adenoma secretes excess ACTH leading to increased cortisol production. Choices B, C, and D are incorrect as they misinterpret the primary source of hormone overproduction in Cushing's disease.

Correct Answer: C

Rationale: Diabetes insipidus is a condition where the kidneys are unable to conserve water, leading to the excretion of large volumes of dilute urine. This is due to either a lack of antidiuretic hormone (ADH) production (central DI) or the kidneys' insensitivity to ADH (nephrogenic DI). Choice A is incorrect as the urine is dilute, not concentrated. Choice B is incorrect as diabetes insipidus results in large, not small, urine volumes. Choice D is incorrect as the urine is dilute, not concentrated. Therefore, choice C accurately describes diabetes insipidus.

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: B

Rationale: The correct answer is B: Dry skin. In hypothyroidism, the thyroid gland does not produce enough thyroid hormone, leading to decreased metabolism. This can result in several symptoms, including dry skin due to reduced sweat gland activity. Hyporeflexia (A) is not a common symptom of hypothyroidism. Oily skin (C) is more commonly associated with hyperthyroidism, where thyroid hormone levels are elevated. Excessive hair growth (D) is not typically seen in hypothyroidism; instead, hair loss is a common symptom.