There are also many synthetic sex steroids. Synthetic androgens are often referred to as anabolic steroids. Synthetic estrogens and progestins are used in methods of hormonal contraception. Ethinylestradiol is a semi-synthetic estrogen. Specific compounds that have partial agonist activity for steroid receptors, and therefore act in part like natural steroid hormones, are in use in medical conditions that require treatment with steroid in one cell type, but where systemic effects of the particular steroid in the entire organism are only desirable within certain limits.
In many contexts, the two main classes of sex steroids are androgens and estrogens, of which the most important human derivatives are testosterone and estradiol, respectively. Other contexts will include progestogens as a third class of sex steroids, distinct from androgens and estrogens. Progesterone is the most important and only naturally-occurring human progestogen. In general, androgens are considered "male sex hormones", since they have masculinizing effects, while estrogens and progestogens are considered "female sex hormones" although all types are present in each sex, albeit at different levels.