Endocrine system antagonists

Endocrine disrupters Chemicals that cause disturbances of the endocrine system (e.g., by acting as agonists or antagonists of the estrogen receptor). 

Norman AW, Ishizuka S, and Okamura WH (2001) Ligands for the vitamin D endocrine system different shapes function as agonists and antagonists for genomic and rapid response receptors or as a ligand for the plasma vitamin D binding protein./owma/ of Steroid Biochemistry and Molecular Biology 76, 49-59. 

Some xenobiotic compounds can have hormonelike effects and cause disruption of the endocrine system. A compound that mimics the action of a particular hormone is termed an agonist, whereas one that blocks its activity is an antagonist. Hormone activity is governed by receptors that recognize the shape of the molecule, so potentially other molecules with suitable structural characteristics can interact with these receptors. There are other potential modes of action of endocrine disrupters. To summarize ... 

The development of new tests and bioassays is likely to lengthen the list of endocrine disrupters. Recent research on hormonal disruption has not only investigated estrogens and androgens as agonists and antagonists but also considered the development of the individual and the presence of compounds that interfere in other hormonal systems, such as the thyroid system. 

Prominent among toxicants that adversely affect both male and female reproductive systems are endocrine disruptors (see Section 9.7). Toxicants that mimic the actions of sex hormones are agonists, and those that prevent hormonal action or bind competitively to hormone receptor sites are antagonists,12 Male patients treated with cimetidine for peptic ulcers have exhibited low sperm counts and abnormal breast enlargement, a condition called gynecomastia. Gynecomastia has also been caused in men working in oral contraceptive production. Ketoconozole inhibits the enzymes required to produce hormones involved in sperm production and can immobilize sperm in seminal fluid. 

---