A patient presents with fatigue, weakness, hyperpigmentation of the skin, and salt craving. Laboratory tests reveal low serum sodium levels and elevated serum potassium levels. Which endocrine disorder is most likely responsible for these symptoms?
Correct Answer: D
Rationale: Addison's disease is a rare endocrine disorder characterized by adrenal insufficiency, leading to a deficiency in cortisol and aldosterone production. The symptoms of Addison's disease include fatigue, weakness, hyperpigmentation of the skin (due to elevated levels of ACTH stimulating melanocytes), and salt craving (due to aldosterone deficiency). Low serum sodium levels and elevated serum potassium levels are also common laboratory findings in Addison's disease, as aldosterone plays a key role in maintaining electrolyte balance. Patients with Addison's disease are at risk of developing an adrenal crisis, which can be life-threatening if not promptly recognized and treated with glucocorticoid and mineralocorticoid replacement therapy.