Mineralocorticoid substitution and monitoring in primary adrenal insufficiency

Patients with primary adrenal insufficiency usually show pronounced impairment of aldosterone secretion and, therefore, require also mineralocorticoid replacement for full recovery. Clinical signs of mineralocorticoid deficiency comprise hypotension, weakness, salt craving and electrolyte disturbances (hyperkalemia, hyponatremia). Mineralocorticoid deficiency is confirmed by demonstration of profoundly decreased aldosterone and highly elevated plasma renin activity (PRA). Standard replacement consists of 9α-fluorocortisol (fludrocortisone) given once daily as a single oral dose (0.05-0.2 mg). Monitoring of mineralocorticoid replacement consists of clinical assessment (well-being, physical examination, blood pressure, electrolyte measurements) and measurement of PRA aiming at a PRA level in the upper normal range. Current replacement regimens may often be associated with mild hypovolemia. Dose adjustments are frequently needed in pregnancy to compensate for the anti-mineralocorticoid activity of progesterone and in high ambient temperature to avoid sodium depletion. In arterial hypertension a dose reduction is usually recommended, but monitoring for hyperkalemia is required.