Triple A Syndrome (Allgrove, AAAS, AR)

A 7-year-old boy of consanguineous parents presents with recurrent hypoglycemic seizures (glucose 38 mg/dL), marked hyperpigmentation of gums and palms, dry eyes requiring artificial tears since infancy, and progressive dysphagia with regurgitation. Investigations show undetectable cortisol with markedly elevated ACTH (>1000 pg/mL), preserved aldosterone levels, and esophageal manometry confirming achalasia. Genetic testing reveals a homozygous nonsense mutation in the AAAS gene on **chromosome 12q13**. Which of the following best explains the pathophysiology of this patient's adrenal insufficiency?