The glucocorticoid receptor as a regulator of cortisol responses in cortisol resistant patients and healthy subjects

Abstract: Glucocorticoids are essential for life, and are involved in growth, reproduction, intermediary metabolism, immune and inflammatory reactions as well as central nervous system and cardiovascular functions. Glucocorticoids are also used as treatment of many diseases. Resistance to exogenous glucocorticoids is sometimes seen in patients treated with glucocorticoids. Resistance to endogenous glucocorticoid is seen in some patients causing a syndrome called primary generalized glucocorticoid resistance. Glucocorticoids exert their effect through the glucocorticoid receptor, which belongs to the nuclear hormone receptor superfamily. The receptor consists of three functional domains, the N-terminal, the DNA binding domain and the ligand binding domain. The overall aim of this thesis was to study the glucocorticoid receptor in patients with primary generalized resistance to glucocorticoids i.e. resistance to endogenous glucocorticoids. In 12 unrelated patients with primary generalized glucocorticoid resistance we identified two novel mutations in the glucocorticoid receptor gene in two different patients, R477H and G679S respectively, situated in the DNA binding domain and in the ligand binding domain of the receptor. The R477H mutation is the only mutation described in the DNA binding domain of the human glucocorticoid receptor. We characterized these two mutations in vitro in terms of ligand binding, DNA binding, transactivation and transrepression as well as studies of crosstalking with the inflammatory transcription factor NFκB. We could demonstrate that the phenotype of the two patients expressing these two mutations correlated to the in vitro findings. We further demonstrated that the R477H and G679S were true mutations and not present as polymorphisms among healthy individuals. Glucocorticoid sensitivity among healthy individuals was also compared between two groups characterized as low and high secretors of urinary free cortisol studied with respect to their responses to a low dose of exogenous glucocorticoid. We concluded that individuals with a low cortisol profile, though still in the normal range, seems to be more sensitive to exogenous cortisol than those with high profile. This could have impact on the response to treatment with exogenous glucocorticoids and the prediction of therapeutic effect and adverse side effects.