Energy Expenditure in 21-Hydroxylase Congenital Adrenal Hyperplasia Patients and Comparison with Predictive Equations

Abstract

Objective: To characterize resting energy expenditure (REE) in patients with classic 21-hydroxylase congenital adrenal hyperplasia (21-OH CAH) using indirect calorimetry and compare it to the most commonly used REE predictive equations. Methods: This case-control study comprised 29 post-pubertal 21-OH CAH patients regularly followed at the University of Campinas. Elevated serum 17-hydroxyprogesterone and CYP21 gene molecular analysis confirmed the diagnosis. A healthy control group paired by age, gender, and body mass index was examined. Dual-energy X-ray absorptiometry (DEXA) measured body compositions. A bioimpedance analyzer determined fat-free mass, and indirect calorimetry using a metabolic cart measured REE. Results: Unlike our initial hypothesis, REE was similar between the groups (18.7 ± 3.1 kcal/kg/day in CAH vs. 20.3 ± 3.5 kcal/kg/day in controls; P = .728). No predictive equations reached the stipulated accuracy criteria, thus lacking validity in REE assessment in adults with the characteristics of the group studied. DEXA analysis revealed higher body fat and diminished nonbone lean mass in 21-OH CAH. Anthropometric and bioelectrical impedance parameters were not significantly different. Conclusion: Classic 21-OH CAH is generally followed in reference centers, which may facilitate indirect calorimetry use for REE measurement. Alternatively, considering our REE findings in adult 21-OH CAH patients, nutrition management based on 25 kcal/body weight/day (measured REE × activity factor 1.2 to 1.3) may be reasonable for current body weight maintenance in these patients. Abbreviations: 17-OHP = 17-hydroxyprogesterone; 21-OH CAH = classic 21-hydroxylase deficiency congenital adrenal hyperplasia; BMI = body mass index; REE = resting energy expenditure; VO2 = volume of oxygen; VCO2 = volume of carbon dioxide.