Testosterone. Computer artwork of a molecule of the male sex hormone testosterone, also known as 17-beta-hydroxy-4-androsten-3-one. Atoms are shown as colour-coded spheres: carbon (C) is purple), hydrogen (H) is white, & oxygen (O) is pink. Test- osterone's chemical formula is C19.H28.O2. It is the main human androgen, the class of steroid hormones which cause the development of male reproductive organs and secondary sex characteris- tics. It is mainly produced in the testes. Testosterone may be used in hormone replacement therapy to treat delayed puberty in boys, some types of impotence, & breast cancer in women.