Endocrinology Practice Questions

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: 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: The correct answer is A: Diarrhea. Addison's disease is a condition where the adrenal glands do not produce enough hormones. Diarrhea is not a typical symptom of Addison's disease. The characteristic features include fatigue, weakness, weight loss, dizziness (B), hyperpigmentation, low blood pressure, dehydration (D), and skin changes like dermatitis is common (C). Therefore, diarrhea does not align with the typical symptoms of 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: A

Rationale: The correct answer is A because parathyroid hormone does not directly stimulate osteoblasts to increase bone formation. Instead, it indirectly increases bone resorption by stimulating osteoclasts. Parathyroid hormone also increases calcium reabsorption from the distal tubule of the kidney (choice C) and inhibits phosphate reabsorption in the proximal tubule of the kidney (choice D). By understanding the physiological actions of parathyroid hormone, we can deduce that direct stimulation of osteoblasts is not one of its functions.