Correct Answer: A

Rationale: In this scenario, the correct answer is the 55-year-old man with new onset headaches that worsen at night and reported mood swings according to his family. These symptoms, especially when combined with nighttime worsening and mood changes, could indicate a serious underlying disorder such as a brain tumor or increased intracranial pressure. Choice B is incorrect as the unilateral throbbing headache with photophobia and nausea is suggestive of migraine headaches, which are usually not associated with serious underlying disorders. Choice C describes symptoms that are more indicative of tension-type headaches rather than a serious underlying disorder. Choice D presents symptoms that are more likely related to hormonal changes and migraines rather than a serious underlying disorder.

Correct Answer: C

Rationale: The correct answer is C: Decline in kidney function. As people age, their kidneys may not work as effectively in conserving water and concentrating urine, leading to a higher risk of dehydration. Choice A is incorrect because more insensible losses do not directly relate to an increased risk of dehydration in the elderly. Choice B, an increase in muscle mass, is not a factor that leads to dehydration. Choice D, a decrease in fat, is also not a direct factor contributing to dehydration in the elderly.

Correct Answer: C

Rationale: Multiple sclerosis is characterized by the immune system mistakenly attacking the myelin sheath in the central nervous system. This results in the formation of lesions that can occur in different parts of the central nervous system, leading to varied symptoms depending on the location of the damage. Choice A is the correct answer because it accurately describes the pathophysiology of multiple sclerosis. Choices B, C, and D are incorrect because they describe mechanisms or locations that are not associated with the pathogenesis of multiple sclerosis.

Correct Answer: C

Rationale: The correct answer is dark urine. Rhabdomyolysis is a condition characterized by the breakdown of muscle tissue, leading to the release of myoglobin into the bloodstream. Myoglobin can cause the urine to appear dark or tea-colored, a condition known as myoglobinuria. This is a classic symptom of rhabdomyolysis. Choices A, B, and D are incorrect as they do not typically present as direct symptoms of rhabdomyolysis. Paresthesias refer to abnormal sensations like tingling or numbness, bone pain is not a primary symptom of rhabdomyolysis, and diarrhea is not a common complaint associated with this condition.

Correct Answer: A

Rationale: Abrupt withdrawal or discontinuation of prednisone, a corticosteroid, can lead to adrenal crisis. This occurs due to the suppression of the adrenal glands' natural cortisol production caused by prolonged exogenous steroid administration. Adrenal crisis presents with symptoms such as weakness, fatigue, abdominal pain, and hypotension. Hypercortisolism (Cushing syndrome) results from chronic excessive exposure to cortisol, not abrupt withdrawal. ACTH stimulation would be expected in response to low cortisol levels, not as a direct consequence of prednisone withdrawal. Thyroid crisis (thyroid storm) is associated with severe hyperthyroidism and is not directly related to corticosteroid withdrawal.