• Estrone and estradiol are female sex hormones known as estrogens. They are responsible for the development of female secondary characteristics and secreted by the ovaries. Estrogens also regulate the menstrual cycle.
• Progesterone is the hormone that is essential for the maintenance of preganancy. It also prevents ovulation during pregnancy.

Scheme 6

In addition to the precursor of all the steroid hormones in animals, cholesterol is also precursor for the synthesis of the bile acids.  For example, the bile acid, cholic acid synthesized in liver, stored in gallbladder and secreted into the small intestine, where it acts as an emulsifying agent so that fats and oils can be digested by water-soluble enzymes.

10.9 Synthetic Steroids

The potent physiological properties of naturally occurring steroids have led to the development of synthetic steroids.  For examples, stanozolol and dianbol are drugs developed in this way exhibit the same muscle-building effect as testosterone.

Some of the synthetic steroids have been found to be more potent than natural steroids. For examples, norethindrone is better than progesterone in arresting ovulation, while RU 486 terminates preganancy within the first nine weeks of gestation. These oral contraceptives have structures similar to that of progesterone.