Testosterone is a steroid hormone secreted by the testes in response to hormones released by parts of the brain. It's responsible for male sexual behavior, sperm development, and secondary sex characteristics including muscle growth. As a molecule, testosterone is chemically related to several other biomolecules present in both men and women.
Physical Properties
The molecule testosterone is entirely composed of only three elements--carbon, hydrogen and oxygen. The "CRC Handbook for Chemistry and Physics" notes that its chemical formula is C19H28O2, meaning that the molecule contains 19 atoms of the element carbon, 28 atoms of hydrogen, and two atoms of oxygen. Its molecular mass is 288.4 amu, or atomic mass units, making it a very heavy molecule. The molecule is tetracyclic, meaning that it consists of four separate rings of carbon atoms that are attached to one another. This conformation of atoms is quite stable. The molecule has a melting point of 311 degrees Fahrenheit, meaning that it would be a solid if purified at room temperature.
Chemical Reactivity and Toxicity
The testosterone molecule consists of very few chemically reactive areas, given its large size. In their book "Biochemistry," Drs. Mary Campbell and Shawn Farrell note that the testosterone molecule consists mostly of carbon-carbon single bonds and carbon-hydrogen single bonds. Both bond types are quite unreactive. In fact, testosterone's job in the body is not to "react," but rather to bind to hormone receptors on target organs. Testosterone, therefore, acts more like a chemical "key" than a chemical reagent, and in binding to receptors, it causes organs to secrete products or engage in particular activities for which the hormone is a necessary initiator. Testosterone does engage in some chemical reactions, however--the liver, for instance, metabolizes testosterone to remove it from the blood. The "Material Safety Data Sheets" for testosterone note that taken internally in large amounts, testosterone can cause gastric upset, vomiting and diarrhea. It's also a known carcinogen--large amounts of it can cause cancer.
Chemical Relatives
Testosterone is made in the body from cholesterol, a closely related and similarly shaped molecule. The series of chemical reactions that produce testosterone from cholesterol involves many enzymes, or proteins that help reactions to take place faster than they otherwise would. Several other steroid hormones are also synthesized by the body from cholesterol--these hormones include estrogen, progesterone and aldosterone, explains Dr. Gary Thibodeau in his book "Anatomy and Physiology."
References
- "CRC Handbook of Chemistry and Physics"; David Lide; 1974
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
- "Material Safety Data Sheet"; Testosterone; Rev September 2009
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
