The science of steroids.

Steroids are complex lipophilic molecules that have many actions in the body to regulate cellular, tissue and organ functions across the life-span. Steroid hormones such as cortisol, aldosterone, estradiol and testosterone are synthesised from cholesterol in specialised endocrine cells in the adrenal gland, ovary and testis, and released into the circulation when required. Steroid hormones move freely into cells to activate intracellular nuclear receptors that function as multi-domain ligand-dependent transcriptional regulators in the cell nucleus. Activated nuclear receptors modify expression of hundreds to thousands of specific target genes in the genome. Steroid hormone actions in the fetus include developmental roles in the respiratory system, brain, and cardiovascular system. The synthetic glucocorticoid steroid betamethasone is used antenatally to reduce the complications of preterm birth. Development of novel selective partial glucocorticoid receptor agonists may provide improved therapies to treat the respiratory complications of preterm birth and spare the deleterious effects of postnatal glucocorticoids in other organs.