Limitations of 17-hydroxyprogesterone in investigating neonatal hyponatraemia

Abstract

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase de ciency is a possible cause of hyponatraemia in the neonate. Elevated 17-hydroxyprogesterone (17-OHP) is considered diagnostic of the condition, although there have been reports of anomalous high concentrations, up to 110 nmol/L, in premature, sick infants subsequently shown to have normal adrenocortical function.We describe a case of a 6-week-old girl with a chest infection and hyponatraemia whose plasma 17-OHP concentration was 300 nmol/L, well within the range associated with 21-hydroxylase de ciency. However, there was no genital ambiguity and plasma cortisol was also signi cantly elevated, raising the possibility of generalized adrenal hyperstimulation rather than CAH. The patient was treated with antibiotic and saline infusions but no steroids. CAH was subsequently excluded by normal 17-OHP and cortisol responses to Synacthen stimulation.In sickness, an increased plasma 17-OHP concentration may not be synonymous with 21-hydroxylase de ciency, even when grossly raised. Simultaneous measurement of plasma cortisol could aid interpretation and avoid potential misdiagnosis, especially in male infants.

Unusual results from immunoassays and the role of the clinical endocrinologist

“…The request form that accompanies the sample must make available information to the laboratory staff on age, sex, ethnic origin, pregnancy and stage of menstrual cycle as appropriate 28,29 . The newborn period is a difficult time to assess hormonal status because of the residual effects of foetal and placental hormones 30 …”

“…28,29 The newborn period is a difficult time to assess hormonal status because of the residual effects of foetal and placental hormones. 30…”

No evidence of an increase in early infant mortality from congenital adrenal hyperplasia in the absence of screening

“…The number of elevated results is unsurprising considering that a study group of infants who subsequently died will consist of many who were gravely ill at the time of newborn screening. Ismail et al described a case of a 6-week-old female with a chest infection and hyponatraemia who had a plasma 17-OHP of 300 nmol/L 22. However the cortisol was extremely high (>1600 nmol/L) and CAH was subsequently excluded.…”