Higher hydrocortisone dose increases bilirubin in hypopituitary patients- results from an RCT

Background Bilirubin has anti‐oxidative and anti‐inflammatory properties, which may explain its proposed protective effects on the development of cardiometabolic disorders. Glucocorticoids affect heme oxygenase regulation in vitro, which plays a key role in bilirubin production. Effects of variations in glucocorticoid exposure on circulating bilirubin levels in humans are unknown. Here we tested whether a higher hydrocortisone replacement dose affects circulating bilirubin in hypopituitary patients. Materials and methods A randomized double‐blind cross‐over study (ClinicalTrials.gov, number NCT01546992) was performed in 47 patients with secondary adrenal failure [10‐week exposure to a higher hydrocortisone dose (0·4–0·6 mg/kg body weight) vs. 10 weeks of a lower hydrocortisone dose (0·2–0·3 mg/kg body weight)]. Results Plasma total bilirubin was increased by 10% from 7 to 8 μM in response to the higher hydrocortisone dose (P = 0·033). This effect was inversely related to age (P = 0·042), but was unaffected by sex, obesity and (replacement for) other hormonal insufficiencies. The higher hydrocortisone dose also resulted in lower alkaline phosphatase (P = 0·006) and aspartate aminotransferase activities (P = 0·001). Conclusion Bilirubin is modestly increased in response to higher glucocorticoid exposure in humans, in conjunction with lower alkaline phosphatase and aspartate aminotransferase activities, which are supposed to represent biomarkers of a pro‐inflammatory state and enhanced liver fat accumulation.