BACKGROUND: Poor response of nasal polyps to glucocorticoids (GCs) may be because of abnormal expression of GC receptors (GR) alpha and beta or to downregulation of GRalpha. We aimed to evaluate the in vivo regulation of GR isoforms in GC-treated nasal polyps and to assess the relationship between clinical response to GCs and GR levels. METHODS: Patients with nasal polyps were randomly (3:1) treated (n = 51) or not (n = 14) with oral prednisone and intranasal budesonide for 2 weeks, plus intranasal budesonide for 10 additional weeks. Nasal symptoms were evaluated. Biopsies were obtained before (w0) and after 2 (w2) and 12 (w12) weeks of treatment, and analysed for their inflammatory content and GR mRNA (10(2) cDNA copies/mug total RNA) and protein (% immunoreactive inflammatory cells) expression. Healthy nasal mucosa (n = 11) was also investigated. Data are presented as median and 25-75th percentile. RESULTS: At w0, nasal polyps expressed less GRalpha mRNA (1343;683-2263; P < 0.05) and GR protein (41;29-54; P < 0.05) than nasal mucosa (2474;1346-2933; 60;51-72, respectively). GRbeta immunoreactivity was higher in nasal polyps (11;4-19; P < 0.05) than in nasal mucosa (5;2-5). At w2, increased GRalpha mRNA (2010;1037-2732; P < 0.01) and GR protein (56;27-71; P = 0.056) were found compared with w0 (1177;759-2058; 37;29-55, respectively). At w12, GRalpha mRNA and GR protein were similar to w0. GRbeta expression was unaltered by treatment. Neither GRalpha nor GRbeta correlated with nasal symptoms. GR immunoreactivity negatively correlated with eosinophils (r = -0.478; P < 0.001). CONCLUSIONS: GRalpha is downregulated in nasal polyps and upregulated by GC treatment. Neither GRalpha nor GRbeta appear to determine the sensitivity to GCs in nasal polyposis.