Tanner scale

The Tanner scale (also known as the Tanner stages) is a scale of physical development in children, adolescents and adults. The scale defines physical measurements of development based on external primary and secondary sex characteristics, such as the size of the breasts, genitalia, testicular volume and development of pubic and axillary hair. This scale was first identified by James Tanner, a British pediatrician, and thus bears his name.

Due to natural variation, individuals pass through the Tanner stages at different rates, depending in particular on the timing of puberty. In HIV treatment, the Tanner scale is used to determine which treatment regimen to follow (adult, adolescent, or pediatric).

Definitions of stages
Adapted from text by Lawrence Neinstein, MD.

Genitals (male)

 * Tanner I : prepubertal (testicular volume less than 1.5 ml; small penis of 3 cm or less) [typically age 9 and younger]
 * Tanner II : testicular volume between 1.6 and 6 ml; skin on scrotum thins, reddens and enlarges; penis length unchanged [9-11]
 * Tanner III : testicular volume between 6 and 12 ml; scrotum enlarges further; penis begins to lengthen to about 6 cm [11-12.5]
 * Tanner IV : testicular volume between 12 and 20 ml; scrotum enlarges further and darkens; penis increases in length to 10 cm and circumference [12.5-14]
 * Tanner V : testicular volume greater than 20 ml; adult scrotum and penis of 15 cm in length [14+]

Breasts (female)

 * Tanner I : no glandular tissue: areola follows the skin contours of the chest (prepubertal) [typically age 10 and younger]
 * Tanner II : breast bud forms, with small area of surrounding glandular tissue; areola begins to widen [10-11.5]
 * Tanner III : breast begins to become more elevated, and extends beyond the borders of the areola, which continues to widen but remains in contour with surrounding breast [11.5-13]
 * Tanner IV : increased breast size and elevation; areola and papilla form a secondary mound projecting from the contour of the surrounding breast [13-15]
 * Tanner V : breast reaches final adult size; areola returns to contour of the surrounding breast, with a projecting central papilla. [15+]

Pubic hair (both male and female)

 * Tanner I : no pubic hair at all (prepubertal Dominic state) [typically age 10 and younger]
 * Tanner II : small amount of long, downy hair with slight pigmentation at the base of the penis and scrotum (males) or on the labia majora (females) [10–11.5]
 * Tanner III : hair becomes more coarse and curly, and begins to extend laterally [11.5–13]
 * Tanner IV : adult-like hair quality, extending across pubis but sparing medial thighs [13–15]|
 * Tanner V : hair extends to medial surface of the thighs [15+]

Criticism
The scale has been criticized by the pornography industry for its potential to lead to false child pornography convictions, such as in the case when government experts used it to assert that pornographic actress Lupe Fuentes was underage. Fuentes personally appeared at the trial and provided documentation that showed that the DVDs in question were legally produced. The author of the classification system himself has argued that age classification utilizing the Tanner stages represents invalid use. Tanner stages do not match with chronological age but rather maturity stages and thus are non-diagnostic for age estimation.