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Congenital Adrenal Hyperplasia

Summary

  • a paediatric endocrinologist should be involved in all cases
  • families will need referral to endocrinologist/geneticist for appropriate counselling
  • affected children usually remain metabolically stable for the first two weeks of life
  • adrenal crises (usually heralded by vomiting and failure to thrive) are often sudden and life threatening
  • salt replacement, in addition to both glucocorticoid and mineralocorticoid replacement is usually required in the first months of life

Introduction

Congenital adrenal hyperplasia (CAH) is an autosomal recessive condition with an incidence of approximately 1 in 12,500 births.

Approximately 95% of cases are due to a deficiency of the enzyme 21-hydroxylase which catalyzes the conversion of progesterone and 17-hydroxyprogesterone (17OHP) to deoxycorticosterone and 11-deoxycortisol respectively. This section will focus upon this most common form of CAH.

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Diagnosis

In the neonatal period CAH may present in one of four ways

  • a virilised female neonate

    The clue that neonates with ambiguous genitalia may have CAH is the presence of pigmentation of the areolae and genital skin. There may also be
    • other affected siblings
    • a history of parental consanguinity
    • significant metabolic derangement
      • hyperkalaemia
      • hyponatraemia
      • metabolic acidosis
      • hypoglycaemia (rarely)

Related symptoms (vomiting, failure to thrive, haemodynamic collapse) do not usually occur until the second to fourth week of life. Hence it is unusual for affected females to present in critical condition, having most commonly been diagnosed in the first few days of life.

Milder degrees of CAH may present in more subtle ways (isolated clitoromegaly, virilisation in early childhood etc) and are usually not associated with metabolic compromise in the neonatal period. Until the diagnosis of CAH is established such neonates should be managed as for the neonate with ambiguous genitalia.

  • a male neonate with metabolic and haemodynamic collapse, aged 2-4 weeks

    Presentation can vary from mild (failure to thrive) to catastrophic (sudden infant death). Frequently, presenting males are assumed to have sepsis. The major clinical clues to CAH are the presence of pigmented genitalia and nature of the electrolyte disturbance.

  • an antenatally diagnosed case of CAH (due to a previously affected sibling)

    The mother will usually have received pre-natal dexamethasone therapy if the fetus is 46XX. If the antenatal treatment has been successful, affected female neonates should not be virilised, however this is not always the case.

  • detection in unambiguous and metabolically stable males from newborn screening programs

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Investigation

  • the diagnosis is usually made after an elevated serum 17OHP levels is found. This metabolite is normally elevated in the fetus during the last trimester and in the immediate postpartum period. Therefore results can be difficult to interpret in premature infants and term infants less than three days of age. Ideally assessment of 17OHP levels should be deferred until after day 3 of age
  • where it is available, a confirmatory urinary steroid profile is extremely useful
  • elevation in adrenal androgens and ACTH levels may also be helpful, but are usually not measured if the electrolyte pattern and 17OHP levels are concordant

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Management

  • if the patient is haemodynamically compromised, resuscitation with intravenous normal saline and hydrocortisone is required
  • hypoglycaemia may need correction with intravenous dextrose but care should be taken with the water load exacerbating hyponatraemia
  • once stabilized, oral hydrocortisone (10-15 mg/m2/day, given tds) and fludrocortisone (0.15 mg/ m2/day, given bd) therapy should be instituted. Additional salt (0.5-1.0 gm/10 kg/day) replacement is usually required although there is some variance in opinion regarding this

Tablets should be ground up between two teaspoons and mixed with a few drops of milk. This solution should be transferred to a small, plastic feeding spoon and deposited on the back of the tongue immediately prior to feeds. Hydrocortisone solutions/suspensions should be avoided, as they are notoriously unstable and inconstant in dose delivery.

Reference

Merke DP, Bornstein SR, Avila NA, Chrousos GP. Future Directions in the Study and Management of Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency. Ann Intern Med 2002 Feb 19; 136(4):320-34

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