Role of 11ßHSD type 2 enzyme activity in essential hypertension and children with chronic kidney disease (CKD).

ABSTRACT

BACKGROUND: The mineralocorticoid receptor is protected from excess of glucocorticoids by conversion of active cortisol to inactive cortisone by enzyme 11ß-hydroxysteroid dehydrogenase type 2 present in the kidney. The metabolites of cortisol and cortisone are excreted in the urine as tetrahydrocortisol (5αTHF+5ßTHF) and tetrahydrocortisone (THE), respectively. HYPOTHESIS: Patients with chronic kidney disease (CKD) and essential hypertension have a functional defect in their ability to convert cortisol to cortisone, thus leading to the activation of mineralocorticoid receptor. OBJECTIVE: The objective of the investigation was to study the ratio of urinary steroids (5αTHF+5ßTHF) to THE in patients with CKD, postrenal transplant, and essential hypertension and to compare the ratio with controls. DESIGN/METHODS: We enrolled 44 patients (17 with CKD, eight postrenal transplant, 19 with essential hypertension) and 12 controls. We measured spot urinary 5α-THF, 5ß-THF, THE, free active cortisol and inactive cortisone by gas chromatography/mass spectrometry. We collected data on age, sex, cause of kidney disease, height, weight, body mass index, blood pressure, serum electrolytes, aldosterone, and plasma renin activity. Blood pressure percentiles and z-scores were calculated. The glomerular filtration rate was calculated using the modified Schwartz formula. RESULTS: The ratios of 5αTHF+5ßTHF to THE were significantly higher in patients with CKD [mean±sd score (SDS)=1.31±1.07] as compared with essential hypertension (mean±SDS=0.59±0.23; P=0.02) and controls (mean±SDS=0.52±0.25; P=0.01). In the postrenal transplant group, the ratio was not significantly different (mean±SDS=0.71±0.55). The urinary free cortisol to free cortisone ratios were significantly higher in the hypertension and CKD groups as compared with the controls. The 5αTHF+5ßTHF to THE ratio negatively correlated with the glomerular filtration rate and positively correlated with systolic and diastolic blood pressure z-scores. The correlation of the blood pressure z-scores with ratios was stronger in the CKD group than the essential hypertension and posttransplant groups. CONCLUSIONS: We have elucidated a functional deficiency of 11ß-hydroxysteroid dehydrogenase type 2 in children with CKD and a subset of essential hypertension. Urinary 5α-THF, 5ß-THF, and THE analysis by gas chromatography/mass spectrometry should be a part of routine work-up of CKD and hypertensive patients.