1. Estrogen Antagonists Compounds which inhibit or antagonize the action or biosynthesis of estrogenic compounds. 2. Antineoplastic Agents, Hormonal Antineoplastic agents that are used to treat hormone-sensitive tumors. Hormone-sensitive tumors may be hormone-dependent, hormone-responsive, or both. A hormone-dependent tumor regresses on removal of the hormonal stimulus, by surgery or pharmacological block. Hormone-responsive tumors may regress when pharmacologic amounts of hormones are administered regardless of whether previous signs of hormone sensitivity were observed. The major hormone-responsive cancers include carcinomas of the breast, prostate, and endometrium; lymphomas; and certain leukemias. 3. Bone Density Conservation Agents Agents that inhibit BONE RESORPTION and/or favor BONE MINERALIZATION and BONE REGENERATION. They are used to heal BONE FRACTURES and to treat METABOLIC BONE DISEASES such as OSTEOPOROSIS 4. Selective Estrogen Receptor Modulators A structurally diverse group of compounds distinguished from ESTROGENS by their ability to bind and activate ESTROGEN RECEPTORS but act as either an agonist or antagonist depending on the tissue type and hormonal milieu. They are classified as either first generation because they demonstrate estrogen agonist properties in the ENDOMETRIUM or second generation based on their patterns of tissue specificity. | 
