How is Addison’s disease treated?

Treatment regimens for Addison’s disease are usually initiated and adjusted by a specialist endocrinologist, but repeat prescriptions may be provided in primary care under a shared-care arrangement. Both glucocorticoid and mineralocorticoid replacement are needed, but androgen replacement is not routinely prescribed in the UK.

Glucocorticoid replacement — hydrocortisone is usually used for glucocorticoid replacement, but longer-acting glucocorticoids, such as prednisolone and dexamethasone, are sometimes used to avoid the peaks and troughs which may occur with hydrocortisone.

The daily adult dosage of hydrocortisone is usually 15 mg to 30 mg in divided doses. Dosage depends on body weight, metabolism, and absorption.

Ideally glucocorticoid replacement should resemble the natural cycle of corticosteroid release.
Three divided doses are usually given (for example 10 mg on waking, 5 mg at noon, and 5 mg in the early evening), as this aims to provide even levels of glucocorticoid throughout the day. Two divided doses are also an option (for example 15 mg in the morning, and 10 mg in the afternoon or early evening), but there is some opinion that this may lead to more variation in cortisol levels.

For people doing shift work, doses of glucocorticoid should follow the person’s daily routine, not the time on the clock. For example, the first dose should be given on getting up after sleep, even if this is not in the morning.

Dosages in children are usually in the region of 4–5 mg/m2 every 8 hours, although the total daily dose may be divided into a larger dose in the morning and a smaller dose in the evening.

Mineralocorticoid replacement — fludrocortisone, which has 125 times the mineralocorticoid action of hydrocortisone, is usually used.

The daily adult dosage of fludrocortisone is usually 50 micrograms to 300 micrograms. Dosage depends on metabolism and exercise levels.

Children and neonates have a much higher mineralocorticoid requirement (5 micrograms/kg) and may need salt supplementation.

At high temperatures and humidity, the fludrocortisone dose may need to be increased to compensate for the increased salt loss from sweating.

Androgen replacement — dehydroepiandrosterone (DHEA) is an androgen made in the adrenal cortex; therefore, levels are decreased in Addison’s disease. DHEA replacement (unlicensed) may be prescribed by some specialists.

G Mohan.

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