Tanner Stages of Puberty

boys

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The presence of pubic hair or armpit odor prior to enlargement of the testicles is the result of adrenal androgens.

In boys, the visible indications of puberty occur as a result of changes in tissues which contain testosterone receptors. Most of that testosterone comes from the testicles. Once the HPG axis becomes active, increases in testicle size provide increased testosterone output, and testosterone drives the visible changes of puberty.

For more information, see the puberty index page.

stage genitals testicle length pubic hair annual height velocity other

I

infrequent erections

less than
1.6 cm
(5/8 in)

villus hair only
(through age 11 years)

5.0 to 6.0 cm
(2 to 2-1/2 in)

adrenarche

II

scrotum skin thins and reddens; frequent erections

2.5 to 3.2 cm
(1 to 1-1/4 in)

sparse, slightly pigmented
(average 12-1/2 years)

7.0 to 8.0 cm
(2-3/4 to 3-1/4 in)

leaner body

III

lengthening of penis

3.3 to 4.0 cm
(1-3/8 to 1-1/2 in)

coarser, darker, curled
(average age 14 years)

8.0 cm
(3-1/4 in)

some temporary swelling of breasts,
voice breaks

IV

thickening of penis, darkening of scrotum skin

4.1 to 4.5 cm
(1-5/8 to 1-3/4 in)

adult type, but not beyond pubic area
(average age 15 years)

10.0 cm
(4 in)

acne, underarm hair, voice deepens

V

adult genitals

4.5 cm
(1-3/4 in)

adult type, spreading onto inner thigh
(average 15-1/2 years)

full height reached at age 18 or 19

beard, continuing muscle dev.