Bayesian population approach to model oscillatory response

Pituitary pars intermedia dysfunction (PPID) is a disease in which the cortisol suppression mechanism through dexamethasone is challenged. Overnight dexamethasone suppression test (DST) protocols are used to test the functioning of this mechanism and to establish a diagnosis for PPID. However, existing DST protocols have been recognized to perform poorly in previous experimental studies, often indicating presence of PPID in healthy horses.  In this study, an NLME approach was used to investigate the IIV in dexamethasone exposure and cortisol response in horses. The aim was to use the adjusted model to scrutinize DST protocol designs.

Felix took advantage of pharmacokinetic/pharmacodynamic (PK/PD) modelling approach to analyse the oscillatory cortisol response and its interaction with dexamethasone. The study resulted in an improved model structure and parameter estimates for cortisol concentration in horses during intervention with dexamethasone.

This work has been done together with Fraunhofer- Chalmers Center for Industrial Mathematics and Swedish University of Agricultural Sciences.