Zuclomifene infertility drug, molecular model. The drug clomifene, used to treat infertility in women, is made up of two components, enclomifene and zuclomifene (shown here). These molecules are geometric isomers, or mirror images of each other. Together, they act on the pituitary gland in the brain, which detects levels of the female sex hormone oestrogen. Fooled into thinking levels of oestrogen are low, the pituitary encourages the release of follicle stimulating hormone (FSH), leading to higher ovulation rates and a greater chance of pregnancy. In this model, atoms are represented by coloured spheres; carbon is purple, hydrogen is white, oxygen is orange, nitrogen is pink, and chlorine is green.