Endocrine Abstracts (2016) 45 P4 | DOI: 10.1530/endoabs.45.P4

Misleading biochemical picture in infants prior to the confirmatory diagnosis of Congenital Adrenal Hyperplasia (CAH)

Zainaba Mohamed, Joanna Benson, James Law, Louise Denvir, Pooja Sachdev & Tabitha Randell

Department of Paediatric Endocrinology and Diabetes, Nottingham Children’s Hospital, University of Nottingham NHS Foundation Trust, Nottingham, UK.

Introduction: Adrenal insufficiency is a rare cause of life-threatening hyponatraemic collapse in the neonatal period. The initial investigations taken at the time of presentation, and prior to the institution of hydrocortisone, are a key step in the diagnostic pathway.

Aim: We present a case series where the initial biochemical test results could have led to a delay in diagnosis or early discontinuation of hydrocortisone.

Case 1: Female (46,XX) term infant presented with genital ambiguity with non-palpable gonads. Initial electrolytes at day 4 of age were normal with normal peak cortisol response (Table 1). Urinary steroid profile (USP) confirmed a diagnosis of 21-Hydroxylase deficiency, which allowed initiation of salt and steroid replacement, averting an adrenal crisis.

Case 2: Term male (46,XY) infant born to mother with 21-hydroxylase deficiency had synacthen test for suspected CAH. The peak cortisol response was satisfactory; infant was discharged with cautious reassurance. However USP later confirmed CAH (3-β-hydroxylase deficiency) and infant was commenced on treatment.

Case 3: 14-day-old male (46,XY) term infant presented with 14% weight loss, salt-wasting crisis and dehydration. He was commenced on steroid replacement prior to a synacthen test. An elevated serum aldosterone level prior to steroid treatment confused the picture, raising the possibility of pseudohypoaldosteronism. A USP confirmed the diagnosis of CAH (21-OH defect).

Table 1 Biochemical results at presentation
CaseAge at presentation (days)Age at testing (days)Na (135–144 mmol/l)K (3.5–5.0 mmol/l)Aldosterone (55–421 pmol/l)Renin mu/l17-OH-P nmol/lSynacthen test Cortisol (nmol/l) in minutes Normal >420 at 30 mins

Conclusions: Two cases showed a normal synacthen response, giving false reassurance of the adrenocortical reserve. This was likely due to cross-reactivity with adrenal fetal steroids. The other showed elevated aldosterone levels, which is occasionally reported due to interference in assay. In suspected cases of CAH, clinicians should be guarded in relying on a single normal or abnormal test. Management should be based on confirmatory USP results.

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