HYBRID GENE OR HYBRID STEROIDS IN THE DETECTION AND SCREENING FOR FAMILIAL HYPERALDOSTERONISM TYPE I

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Abstract
SUMMARY: 1. Early diagnosis of Familial Hyperaldosteronism Qpe I (FH‐I, glucocorticoid‐suppressible hyperaldosteronism) in asymptomatic, affected individuals is essential if death from stroke is to be prevented.2. In 21 patients with FH‐I (presence of the causative hybrid 11β‐hydroxylase/aldosterone synthase gene confirmed by Southern blot testing), various biochemical parameters were compared as possible screening tests. Hypokalaemia and elevated plasma aldosterone each detected only two (10%) of the affected individuals.3. Plasma renin activity 19 (90%) and aldosterone/renin ratio 18 (86%) were more reliable but not free from false negatives.4. Levels of the urinary ‘hybrid’ steroid, 18‐oxocortisol, were elevated (P <0.01) in all 15 patients tested (138.2 ± 17.4 μg/g creatinine, range 41.6–281.0 μg/g) with no overlap when compared with 11 normals (9.7 ± 1.3μg/g, range 2.8–17.4 μg/g).5. We conclude that measurement of urinary ‘hybrid’ steroids is probably the most rapid and reliable biochemical screening test currently available for FH‐I, with confirmation dependent on demonstration of the hybrid gene by genetic techniques.