Depending on the number and character of their functional groups, steroid molecules may show diverse reactivities. Moreover, the reactivity of a functional group varies according to its location within the molecule (for example, esters are formed readily by 3-OH groups but only with difficulty by the 11β-OH group). An important property of steroids is polarity —., their solubility in oxygen-containing solvents (., water and alcohols ) rather than hydrocarbon solvents (., hexane and benzene ). Hydroxyl, ketonic, or ionizable (capable of dissociating to form electrically charged particles) groups in a steroid molecule increase its polarity to an extent that is strongly influenced by the spatial arrangement of the atoms within the molecule.
The pancreas produces insulin and glucagon, which function in opposing fashion to regulate blood sugar (glucose) concentration. When blood glucose level rises—for example, after eating a sugar-rich meal—insulin lowers it by stimulating glucose storage in liver and muscle cells as long chains of glucose called glycogen . Conversely, between meals, blood glucose level decreases. In response, the pancreas releases glucagon, which stimulates glycogen breakdown and subsequent release of glucose into the bloodstream. One of the most well characterized endocrine disorders is diabetes mellitus, resulting from hyposecretion of insulin or, more commonly, target cell insensitivity to it.