The Influence of Different Hydrocortisone Replacement Doses on the Partitioning and Flexibility of Ectopic Lipids in Patients With Corticotropic Hypopituitarism

Overview

This study aims at assessing the effect of today's standard of hydrocortisone dosage versus previous hydrocortisone dosage on flexibility and partitioning of ectopic lipid depots (IMCL and IHCL) after a standardised fat load followed by a short-term aerobic exercise in patients with corticotropic pituitary insufficiency.

Background The investigators and others have shown that long-term hydrocortisone replacement therapy at higher doses of hydrocortisone replacement therapy at higher doses of hydrocortisone replacement (as previously recommended) is associated with higher mortality. The pathophysiology for the association of hydrocortisone-replacement dose and mortality remains unclear. A possible underlying mechanism is nonalcoholic fatty liver disease which is more prevalent in patients with hypopituitarism. Patients with non-alcoholic fatty liver disease are at a higher risk for overall-mortality. It remains to be established whether the insulin resistance, associated with increased intrahepatocellular lipids and increased intramusculoskeletal lipids, is implicated in the pathophysiology of these epidemiological findings. Interestingly, it has been shown that a reduction of hydrocortisone replacement dose from 20-30mg/d to 10-15mg/d resulted in a loss of body fat and a significant decrease of plasma total cholesterol and triglyceride concentration. The effect of IMCL and IHCL is so far unknown. Patients with hypopituitarism with hydrocortisone replacement therapy provide a unique disease model to study the short-term effects of previously recommended dose (higher dose) of hydrocortisone versus lower dose of HC replacement therapy on ectopic lipids (IMCL; IHCL) lipids, as well as on subcutaneous and visceral fat mass and on parameters of insulin resistance. Combining MRI and MR-spectroscopy techniques, different fat mass (subcutaneous and visceral) and ectopic lipids can be repeatedly and non-invasively assessed. Objective To investigate the impact of today's standard of hydrocortisone dosage (lower) versus previous (higher) hydrocortisone dosage on flexibility and partitioning of ectopic lipid depots after a standardised fat load followed by a short-term aerobic exercise in patients with corticotropic pituitary insufficiency. Methods Ectopic lipids are measured by MR-spectroscopy, separate assessment of visceral and subcutaneous fat mass will be performed by MR-imaging, standardized exercise capacity test using spiroergometry. Short-time exercise consists of 2h aerobic cycling at 50% VO2max. Laboratory analysis include lipid profile, free fatty acids, HOMA-Index, hormones.