Although testosterone was not isolated until 1935, four years after its metabolite androsterone, the basic origins and effects of the substance have been known for a much longer period of time. Indeed, as early as the 1700s, testicular transplant experiments linked castration to the physiological and behavioral changes that are commonly associated with decreased levels of testosterone production in the male body.

View a second and third image of Testosterone

Testosterone is the primary male sex hormone, but is also found in women, though in much smaller amounts. An average man, for instance, may contain as many as 1,000 nanograms of testosterone in a deciliter of blood plasma, while a typical female does not usually exhibit more than 60 nanograms of the hormone in the same amount of plasma. The location of testosterone production is also different between the sexes, males producing the substance primarily in the testes and females manufacturing it in the ovaries and adrenal glands. Testosterone can be synthesized in the laboratory as well, in which case it generally occurs as a white crystalline powder that is virtually insoluble in water.

Important in a number of ways, testosterone must be present in a fetus in order for the child to develop male genitalia. Later in life, during puberty, testosterone is responsible for the further development of the male sex organs, the deepening of the voice, and the growth of facial hair. The hormone is also associated with protein synthesis stimulation and increased muscle development. It is for this latter effect of testosterone that steroids similar to the hormone have been utilized as performance-enhancing drugs, especially by athletes. However, an increased awareness of the harmful side effects of steroid usage may have helped stem their popularity in recent years. Medical use of testosterone includes treatments for frigidity, impotence, and certain varieties of breast cancer.

Questions or comments? Send us an email.

© 1998-2022 by Michael W. Davidson and The Florida State University. All Rights Reserved. No images, graphics, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.

This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.

Last modification: Friday, Nov 13, 2015 at 02:19 PM

Access Count Since November 20, 2003: 14188

All of the images in this gallery were captured with a QImaging Retiga camera system.
For more information on these cameras, use the button below to access
the QImaging website:

For more information on microscope manufacturers,
use the buttons below to navigate to their websites: