Which Tanner stage indicates a penis length unchanged during puberty?

The Tanner stages are a system used to describe the development of secondary sexual characteristics in children and adolescents. These stages reflect physical maturation in relation to puberty.

In Tanner Stage I, prepubertal boys typically have a penis that is about 3 centimeters in length and does not change or grow. Puberty marks the beginning of significant physical changes, including the growth of genitalia.

Tanner Stage II marks the onset of puberty. At this stage, there is some increase in testicular volume and the appearance of pubic hair. However, the penis remains the same size as in Stage I—there has not yet been a noticeable change in its length.

As the stages progress to Tanner Stage III and beyond, the penis begins to increase in length and girth, along with further development of pubic hair and other secondary sexual characteristics. Therefore, Tanner Stage II is the correct indication of a penis length that remains unchanged during the initial phase of puberty.