Secondary adrenal insufficiency laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Laboratory Findings
ACTH Stimulation Test
If the person is in adrenal crisis, the ACTH stimulation test[1] may be given. If not in crisis, cortisol, ACTH, aldosterone, renin, potassium and sodium are tested from a blood sample before the decision is made if the ACTH stimulation test needs to be performed. X-rays or CT of the adrenals may also be done. The best test for adrenal insufficiency of autoimmune origin, representing more than ninety percent of all cases in a Western population, is measurement of 21-hydroxylase autoantibodies.
| Source of pathology | CRH | ACTH | DHEA | DHEA-S | cortisol | aldosterone | renin | Na | K | Causes5 |
| hypothalamus (tertiary)1 |
low | low | low | low | low3 | low | low | low | low | tumor of the hypothalamus (adenoma), antibodies, environment (i.e. toxins), head injury |
| pituitary (secondary) |
high2 | low | low | low | low3 | low | low | low | low | tumor of the pituitary (adenoma), antibodies, environment, head injury, surgical removal6, Sheehan's syndrome |
| adrenal glands (primary)7 |
high | high | high | high | low4 | low | high | low | high | tumor of the adrenal (adenoma), stress, antibodies, environment, Addison's Disease, trauma, surgical removal (resection), miliary tuberculosis of the adrenal |
| 1 | Automatically includes diagnosis of secondary (hypopituitarism) |
| 2 | Only if CRH production in the hypothalamus is intact |
| 3 | Value doubles or more in stimulation |
| 4 | Value less than doubles in stimulation |
| 5 | Most common, does not include all possible causes |
| 6 | Usually because of very large tumor (macroadenoma) |
| 7 | Includes Addison's disease |
Routine Investigations
- Complete blood count and differential count - Eosinophilia and lymphocytosis (increased number of eosinophils or lymphocytes, two types of white blood cells). Normocytic anemia may be present.
- Serum ACTH levels - elevated in primary adrenal insufficiency and decreased in secondary form.
- Hypoglycemia - low blood sugar (worse in children)
- Serum electrolytes:
- Hyponatraemia - (low blood sodium levels)
- Hyperkalemia - (raised blood potassium levels), due to loss of production of the hormone aldosterone
- Mild hypercalcemia - in 20% patients
- Mild non–anion-gap metabolic acidosis
- Serum cortisol - decreased (<25mcg/dL)
- Urine and sweat sodium - elevated
- Elevated BUN and creatinine - when hypovolemia is the cause.
- Prolactin - mild elevation may be present.