Addison’s disease is a rare disorder of the adrenal gland that results in deficiencies of the hormones cortisol and aldosterone. It is also known as primary adrenal insufficiency or hypoadrenalism.

Cortisol deficiency results in the non-specific symptoms of weakness, fatigue, anorexia, weight loss, vomiting and abdominal pain. Aldosterone deficiency causes hyponatraemia, salt craving, and postural hypotension. A high proportion of patients have a normal serum potassium at presentation. Addison’s may present with hypoglycaemia, which can result in neurological injury. It also results in excess production of the pituitary hormone adrenocorticotropic hormone ACTH, which causes skin pigmentation.

Addison’s disease in children is easily ‘missed’ because of its non-specific symptoms, its rarity (1:10,000), and because doctors have a low index of suspicion for the diagnosis. In children, boys constitute 70% of cases, whereas in adults the majority (70%) are women.

Case study

A 13-year-old boy attended his Emergency Department with a three-week history of abdominal pain, nausea, lethargy, and weight loss. Serum sodium was low at 129 mmol/L. The serum potassium was normal at 3.8mmol/L as was the serum glucose. A diagnosis of gastritis was made, and he was prescribed intravenous fluid and anti-emetics. He was discharged after two days having improved, and his serum sodium was still slightly low at 133 mmol/L pre-discharge.

He had three further admissions over six months with similar symptoms and a persistently low sodium. An eating disorder was considered. A cortisol level was requested but the result was not checked.

He presented to another hospital with similar symptoms six months later. A cortisol level of 34 nmol/L at 8am was noted and a Synacthen test confirmed the diagnosis of Addison’s disease.

Expert witnesses in this case noted the failure to follow up on the result of the initial cortisol blood test and the failure to investigate a persistently low sodium level.

Diagnostic pitfalls

• As in the case outlined above, the possibility of Addison’s Disease is often not considered in those presenting with abdominal symptoms, lethargy, weight loss and hyponatraemia. In such cases, postural hypotension and the presence of skin pigmentation should be looked for.
• It is important to look for pigmentation in the areas not exposed to the sun – palmar creases, axillae, and at pressure points – knuckles, elbows, knees, scars. Blue-black pigmentation of the oral mucosa is another sign seen in some cases. In the rare cases of adrenocorticoid insufficiency due to hypopituitarism, increased pigmentation will be absent.
• Physicians are often falsely reassured by the normal potassium concentration.
• In the case described above, a serum cortisol was taken but the result was not checked. The result must always be checked by the doctor who ordered the test. If the doctor is unable to interpret the test, they should seek specialist advice.

Understanding cortisol levels

• The evaluation of serum cortisol values is often poorly understood by non-endocrinologists. If the ordering doctor is not able to interpret the result, specialist advice must be sought.
• Any cortisol values less than 100 nmol/L are highly suggestive of adrenocortical insufficiency, while a value greater than 500nmol/l virtually excludes it. A random cortisol is best taken in the morning when cortisol levels should be at their highest.
• An ACTH test should be taken at the same time as the serum cortisol. In children with Addison’s disease, the ACTH values are very high 654-1413 pg/ml (normal 11-82pg/ml). In the rare cases of adrenocorticoid insufficiency due to hypopituitarism, the ACTH levels will be low.

We recommend that if a child presents on more than two occasions, with a concerning and, as yet unexplained set of symptoms, a second opinion should be sought.

References available upon request.

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