Case report: A 67-year-old female with untreated congenital adrenal hyperplasia (21-hydoxylase deficiency) was diagnosed with bilateral vulval carcinomata. She was referred to another unit with serum sodium of 121 mmol/l, potassium 4.6 mmol/l and 17-hydroxyprogesterone of 714 nmol/l (014 nmol/l). A short synacthen test performed in the evening demonstrated a baseline cortisol of 558 nmol/l, rising to 643 nmol/l at 80 min. The baseline cortisol was deemed adequate but in view of the stunted rise following synacthen, steroid cover for surgical procedures was advised.
Despite surgical resection, radiotherapy and chemotherapy, the vulval carcinomata recurred. She was then admitted to our hospital unwell with BP 79/50 mmHg. Blood tests showed sodium 119 mmol/l, potassium 5.8 mmol/l and 9am cortisol of 1357 nmol/l. Further 9am investigations showed a repeat cortisol of 1350 nmol/l, testosterone 13.6 nmol/l (0.11.5 nmol/l), FSH 2.9 IU/l, LH<0.2 IU/l, 17-hydroxyprogesterone 470 nmol/l (014 nmol/l), ACTH 371 ng/l (040 ng/l), and dehydroepiandrosterone 2.1 μmol/l (04.6 μmol/l). 24 h urine collections for free cortisol were raised at 378 nmol/day and 483 nmol/day (0260 nmol/day).
Clinically there was evidence of hypoadrenalism but there was biochemical evidence of hypercortisolaemia. MRI pituitary to rule out Nelsons syndrome was normal. The possibility of cortisol assay interference was considered accounting for the elevated serum and urine cortisol. Her 24-h urine sample was then analysed at two national reference laboratories who confirmed steroid precursor assay interference accounting for the markedly elevated cortisol measurements.
She unfortunately succumbed to her carcinoma (on steroid replacement therapy).
Discussion: This case demonstrates how tests can be misleading. The clinical picture indicated a hyopadrenal state (hyponatraemia/hyperkalaemia/hypotension) but the measured cortisol was falsely reassuring. This serves us to remember that a good clinical assessment is crucial.