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Difficulty: MediumPediatric Endocrine Disorders

An 11-year-old boy is brought to the emergency department by his parents after he fainted during a soccer game. Over the past three months, he has experienced worsening fatigue, unexplained weight loss, and recurrent episodes of vague abdominal pain and nausea. His parents mention that he has developed an intense craving for salty foods. On physical examination, his temperature is 37.0∘C37.0^\circ\text{C} (98.6∘F98.6^\circ\text{F}), blood pressure is 82/50 mmHg82/50\text{ mmHg} while supine and drops to 68/40 mmHg68/40\text{ mmHg} upon standing, and pulse is 115/min115\text{/min}. He appears lethargic. There is noticeable darkening of the skin, particularly over the palmar creases, elbows, knees, and buccal mucosa.

Initial laboratory evaluation reveals:
Serum sodium: 128 mEq/L128\text{ mEq/L}
Serum potassium: 6.1 mEq/L6.1\text{ mEq/L}
Serum chloride: 95 mEq/L95\text{ mEq/L}
Serum bicarbonate: 16 mEq/L16\text{ mEq/L}
Blood urea nitrogen: 26 mg/dL26\text{ mg/dL}
Serum creatinine: 0.9 mg/dL0.9\text{ mg/dL}
Serum glucose: 58 mg/dL58\text{ mg/dL}

Which of the following pairs of baseline hormone levels is most likely to be present in this patient prior to any intervention?

  1. A
    Decreased adrenocorticotropic hormone (ACTH) and decreased plasma renin activity
  2. B
    Decreased adrenocorticotropic hormone (ACTH) and elevated plasma renin activity
  3. Elevated adrenocorticotropic hormone (ACTH) and elevated plasma renin activityAnswer
  4. D
    Elevated adrenocorticotropic hormone (ACTH) and decreased plasma renin activity
  5. E
    Normal adrenocorticotropic hormone (ACTH) and normal plasma renin activity

Answer

The correct answer is the option stating elevated adrenocorticotropic hormone (ACTH) and elevated plasma renin activity.
The correct answer states that both ACTH and plasma renin activity are elevated. This patient's presentation of fatigue, weight loss, salt craving, hyperpigmentation, orthostatic hypotension, hyponatremia, hyperkalemia, and hypoglycemia is classic for primary adrenal insufficiency (Addison disease). In primary adrenal insufficiency, the entire adrenal cortex is destroyed. The resulting deficiency of cortisol removes negative feedback on the pituitary gland, leading to increased secretion of ACTH and melanocyte-stimulating hormone (which causes the pathognomonic hyperpigmentation). Simultaneously, the deficiency of aldosterone causes renal sodium wasting, volume depletion, and potassium retention. The resulting hypovolemia and hyponatremia stimulate the juxtaglomerular cells in the kidneys to secrete large amounts of renin, resulting in highly elevated plasma renin activity.

Step-by-Step Solution

1
Identify the clinical syndrome presented by the patient.
The patient presents with orthostatic hypotension, fatigue, weight loss, salt craving, hyperpigmentation, hyponatremia, hyperkalemia, and hypoglycemia.
Recognizing this constellation of symptoms and laboratory findings is essential for diagnosing primary adrenal insufficiency (Addison disease).
2
Determine the status of the hypothalamic-pituitary-adrenal (HPA) axis.
The hyperpigmentation indicates elevated levels of pro-opiomelanocortin (POMC) cleavage products, including ACTH and melanocyte-stimulating hormone (MSH). This occurs due to a lack of negative feedback from cortisol.
Primary adrenal cortex destruction leads to cortisol deficiency, which powerfully stimulates the pituitary gland to overproduce ACTH.
3
Determine the status of the renin-angiotensin-aldosterone system (RAAS).
The patient has severe volume depletion, hyponatremia, and hyperkalemia, which are signs of mineralocorticoid (aldosterone) deficiency. This state strongly stimulates the release of renin from the kidneys.
Aldosterone deficiency leads to renal salt wasting and hypovolemia, triggering a compensatory increase in plasma renin activity to attempt blood pressure maintenance.

Key Concept

Primary adrenal insufficiency (Addison disease)
Estimated Time:1m 30s
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Topics

Pediatric Endocrine Disorders

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