Secondary adrenal insufficiency

Question 1

Definition

Answer 1

Low cortisol & DHEA (androgen that is converted to testosterone) secretion from adrenal glands due to inadequate ACTH secretion from anterior pituitary gland.Reduction in CRH from hypothalamus and/or ACTH from anterior pituitary (due to hypothalamic-pituitary disease or long-term exogenous steroids) results in decreased cortisol & DHEA release from zona fasciculata of adrenal glands. **Mineralocorticoid production remains intact as aldosterone is under control of RAAS not HPA axis **.

Question 2

Cause

Answer 2

Most common = **long-term exogenous steroids **(mimic cortisol & suppress CRH from hypothalamus & ACTH from anterior pituitary -> zona fasciculata atrophies & endogenous cortisol production decreases)
Less common = pituitary insufficiency or hypothalamic-pituitary disease

Question 3

Pathophysiology

Answer 3

Low ACTH results in lack of stimulation of zona fasciculata of adrenal glands-> low cortisol.
Mineralocorticoid (aldosterone) production remains intact as aldosterone in under control of RAAS; androgen production remains intact.

Question 4

Signs & symptoms

Answer 4

Signs:
Postural hypotension (cortisol normally increases BP by increasing sensitivity of alpha-1 adrenergic receptors in VSM to catecholamines)
Hypoglycaemia (due to low cortisol, cortisol raises plasma glucose)
Loss of pubic & axillary hair in women (low androgens)

Sx:
Depression
Fatigue/lethargy
Weight loss & anorexia

Non-specific symptoms:
Abdominal pain
Nausea & vomiting

Question 5

Investigations (no gold standard)

Answer 5

Morning 9AM serum cortisol- low
Plasma ACTH- low
Plasma aldosterone- normal
Plasma renin- normal

Question 6

Treatment

Answer 6

• If the cause is exogenous steroids, wean off oral steroids slowly to allow adrenal glands to recover & boost endogenous cortisol production (steroids normally suppress HPA axis). Abrupt cessation of oral steroids can cause adrenal crisis.
• Give oral hydrocortisone (glucocorticoid to replace cortisol)