Which of the following statements best describes diabetes insipidus?

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: 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: B

Rationale: Step-by-step rationale for why answer B is correct: 1. Cushing's syndrome is characterized by excess cortisol production. 2. Women are more likely to develop Cushing's syndrome due to hormonal differences. 3. Women have higher cortisol levels naturally, making them more susceptible. 4. Men can still develop Cushing's syndrome but at a lower rate compared to women. Summary: A: Incorrect, as women are more likely to develop Cushing's syndrome. C: Incorrect, as the incidence is higher in women due to hormonal factors. D: Incorrect, as it refers to thyroid hormones, not cortisol in Cushing's syndrome.

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.

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.