The Tanner stages, also known as Tanner scaling, are a system used to track the development and progression of secondary sex characteristics during puberty. Developed by Dr. James Tanner, a British pediatrician, this scale is divided into five stages and is based on external physical development characteristics. It’s widely used in both clinical settings and research to assess and understand the changes that occur during puberty.

Tanner Stages in Individuals with Ovaries:

1. Stage 1:
   • Pre-pubertal stage with no visible signs of puberty.
   • The ovaries and uterus are child-sized.
2. Stage 2:
   • Breast development begins with the appearance of small, firm, tender lumps under the nipples, known as breast buds.
   • The start of pubic hair growth, which is usually fine and straight.
3. Stage 3:
   • Breasts continue to grow and become more rounded.
   • Pubic hair becomes darker and starts to curl.
4. Stage 4:
   • Breast development continues with the formation of a secondary mound above the primary breast contour.
   • Pubic hair is now coarse, curly, and thick, but not yet covering the entire pubic area.
5. Stage 5:
   • Mature adult breasts are formed.
   • Pubic hair extends to the inner thighs and resembles adult hair in coarseness and pattern.

Tanner Stages in Individuals with Testes:

1. Stage 1:
   • Pre-pubertal stage with no visible signs of puberty.
   • The testes, scrotum, and penis are about the same size and proportion as in early childhood.
2. Stage 2:
   • Enlargement of the testes and scrotal skin begins to thin and redden.
   • Initial pubic hair growth, which is soft and lightly colored.
3. Stage 3:
   • Growth of the testes and penis (length more than breadth).
   • Pubic hair becomes darker and starts to curl.
4. Stage 4:
   • Further growth of the testes and penis with development of the glans.
   • Pubic hair is now coarse and curly, similar to adult hair but covering a smaller area.
5. Stage 5:
   • Testes, scrotum, and penis are fully developed to adult size and shape.
   • Pubic hair has spread to the inner thighs and is in an adult pattern.

The Tanner stages provide a framework for understanding the physical changes of puberty but don’t encompass the hormonal, emotional, and cognitive changes that also occur. It’s important to recognize that individuals may progress through these stages at different rates, and the age at which these changes begin can vary widely. Tanner staging is used both for assessing normal adolescent development and for planning gender-affirming treatments for transgender and gender-diverse youth.