Fig. 1

Sex steroid effects on bronchial asthma. It is recognized that asthma is a multifactorial disease involving the effects of allergic, infectious and environmental triggers on both the immune system and structural cells of the bronchial airway. Overall, inflammation drives structural and functional airway obstruction leading to epithelial thickening, increased mucus production, proliferation of epithelial, smooth muscle and fibroblast cells, remodelling of the extracellular matrix and overall airway hyperreactivity and fibrosis. Here, studies to-date suggest complex effects of oestrogen vs. progesterone vs. testosterone on relevant cell types, involving both cooperative vs. opposing effects of the different sex steroids within a cell type, but not necessarily across cell types. For example, dendritic cells, mast cells, CD4+ T lymphocytes (Th2), and eosinophils are particularly important. The effects of oestrogen (E), progesterone (P), or testosterone (T) on these immune cells can vary substantially, particularly in the context of concentration, timing and duration [19]