From the Guidelines
For a 48-year-old female with an ACTH level of 6 pg/mL and an incomplete morning cortisol value, further testing is needed to determine the significance of these levels and to guide management. The patient's ACTH level is at the lower end of the normal range, which could suggest secondary adrenal insufficiency where the pituitary isn't producing enough ACTH to stimulate the adrenal glands 1. To evaluate adrenal function, I recommend obtaining a complete morning cortisol level (ideally drawn between 7-9 AM) and potentially performing an ACTH stimulation test. If the morning cortisol is low (below 5 μg/dL) along with the low-normal ACTH, the patient may need glucocorticoid replacement therapy, typically starting with hydrocortisone 15-20 mg daily in divided doses (typically 10-15 mg in morning and 5 mg in afternoon) 1. Additional workup should include:
- Comprehensive pituitary function testing to rule out other hormonal deficiencies
- Pituitary imaging (MRI) to identify potential causes such as pituitary tumors or empty sella syndrome Symptoms to monitor include:
- Fatigue
- Weakness
- Weight loss
- Nausea
- Orthostatic hypotension The patient should be educated about stress dosing during illness and provided with an emergency kit containing injectable hydrocortisone and medical alert identification 1. It's also important to note that the diagnosis of primary adrenal insufficiency (PAI) should be considered in patients presenting with unexplained collapse, hypotension, vomiting, or diarrhea, and that treatment of suspected acute adrenal insufficiency should never be delayed by diagnostic procedures 1. However, the provided information is not sufficient to make a definitive diagnosis, and further evaluation is necessary to determine the best course of action.
From the Research
Adrenocorticotropic Hormone (ACTH) and Morning Cortisol Levels
- An ACTH level of 6 and a morning cortisol level in a 48-year-old female can be significant in assessing the function of the hypothalamic-pituitary-adrenal (HPA) axis 2.
- The HPA axis can be suppressed due to prolonged use of exogenous glucocorticoids, leading to adrenal insufficiency 3, 2.
- A study found that ambulatory early morning cortisol was the only independent predictor of adequate short Synacthen test (SST) response, which assesses HPA axis recovery after prolonged glucocorticoid use 2.
- The relationship between cortisol levels and hemodynamic improvement in patients with septic shock has also been studied, with findings suggesting that cortisol production can be considered "inadequate" in some patients 4.
- In patients cured from endogenous Cushing syndrome, the pituitary corticotroph is not the rate limiting step in the postoperative recovery of the HPA axis, and the locus of the defect resides in the hypothalamic CRH neuron and/or its higher regulatory inputs 5.
Clinical Implications
- The assessment of ACTH and morning cortisol levels can help diagnose adrenal insufficiency, Cushing syndrome, and other disorders affecting the HPA axis 6, 2.
- The use of glucocorticoids can lead to suppression of the HPA axis, and the recovery of the axis can be predicted by ambulatory early morning cortisol levels 2.
- The management of patients with HPA axis disorders requires careful consideration of the underlying cause and the use of appropriate diagnostic tests and treatments 3, 6, 2.