Case Presentation: A 12-year-old girl presented with restrictive eating, weight loss (BMI 12.17 kg/m2; -4.10 SD), and orthostatic hypotension. She was admitted to a tertiary referral children’s hospital and placed on an eating disorder protocol involving scrutiny of intake and output, electrolyte monitoring, supplemental nutrition, and strict bedrest. Her cachectic appearance, apparent food refusal, nausea, and vomiting were thought to be consistent with a restrictive eating disorder. Psychosocial stressors were present but she denied perceptions of herself as fat or fear of gaining weight. Her weight loss continued despite adherence to the protocol and her medical management was complicated by persistent orthostatic hypotension and hyponatremia (126-129 mEq/L) without hyperkalemia. Differential diagnoses considered included renal tubular salt wasting, hyponatremic volume depletion, water intoxication, or an endocrine disorder. She had a normal brain MRI. Subspecialty consultation noted bronzed skin, and subsequent 8 a.m. cortisol testing (0.3 mcg/dL) and confirmatory 250 mcg ACTH stimulation testing confirmed severe primary adrenal insufficiency, which was later confirmed by an extremely elevated ACTH level (3345 pg/mL). The patient received stress-dose glucocorticoid therapy with near-immediate resolution of her hyponatremia, orthostatic hypotension, and nausea. She was discharged on maintenance glucocorticoid and mineralocorticoid replacement. Several months into treatment her weight had increased by 0.9 SD from time of admission.

Discussion: While eating disorders are common diagnoses for young women with weight loss, it is important to consider a broad differential diagnosis. Adrenal insufficiency is an important consideration, and other diagnoses to consider include thyroid dysfunction, type 1 diabetes, malignancy, inflammatory bowel disease, and celiac disease. This case was made difficult because of many similarities between the patient’s presentation and classic eating disorder signs and symptomatology. However, she did not respond to standard treatment, and further testing revealed her underlying adrenal insufficiency.  It is possible for an eating disorder to coincide with, or be exacerbated by, a non-psychiatric medical pathology. However, this is unlikely in this case, as the patient reversed her weight loss after treatment of her underlying disorder.

Conclusions: Adrenal insufficiency can present with symptoms similar to an eating disorder. An 8 a.m. cortisol level can screen for adrenal insufficiency. The diagnosis is confirmed with ACTH stimulation testing, serum ACTH levels, and detection of adrenal autoantibodies. It is treated with glucocorticoid and mineralocorticoid supplementation. Without glucocorticoid replacement, patients may present with an acute adrenal crisis. Had this diagnosis been missed, this patient’s clinical course may have been catastrophic.