Stages of Puberty: In Boys and Girls

The Tanner scale (also known as the Tanner stages or Sexual Maturity Rating (SMR)) 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, genitals, testicular volume, and development of pubic hair.

Tanner stage 1: In Tanner stage 1, there aren’t any obvious physical changes, but it describes the child’s appearance before any physical signs of puberty appear. These initial signs, although not visible, usually begin around the age of 8 years in girls and around 10 years in boys. The brain starts sending signals to the body, getting the body ready for physical changes. The hypothalamus is a gland that releases gonadotropin-releasing hormone (GnRH). GnRH stimulates the pituitary gland, a small gland under the brain that secretes hormones that regulate other glands in the body and body functions, such as growth hormone (GH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH).

Tanner stage 2: In Tanner stage 2, the early physical changes of puberty begin to appear.

Girls: The physical changes of puberty begin between the ages of 9 and 11 years. The signs include:

• Breast “buds” form under the nipple.
• Itching and tenderness are felt over and around the nipples.
• Breast buds may be of different sizes and grow at different rates.
• The areola (the darker area around the nipple) becomes larger.
• Small amounts of pubic hair start appearing.
• The size of the uterus increases.

Some girls may have their first period during this stage. Girls with higher body mass index may experience an earlier onset of puberty. 

Boys: Puberty usually starts around the age of 11 years in boys.

• The testicles begin to enlarge.
• Small amount of pubic hair forms at the base of the penis.

Tanner stage 3: Physical changes are becoming more obvious and visible.

Girls: Physical changes in girls begin after the age of 12 years. These changes include:

• Breast “buds” continue to grow.
• Pubic hair becomes thicker and curly.
• Hair starts forming under the armpits.
• Acne may appear on the face, upper chest, and back.
• The growth rate is the highest during this stage (around 3.2 inches per year).
• Fat builds up in the hips and thighs.
• Body odor may develop at this stage or earlier.

Boys: Physical changes in boys usually start around the age of 13 years. These changes include:

• The penis and testicles continue to grow bigger.
• Some breast tissue may develop under the nipples, which usually disappears after a few years.
• Boys may have wet dreams (ejaculation at night).
• Voice begins to change; it may “crack”.
• Muscles get larger.
• Height increases at the rate of 2-3.2 inches per year.
• Body odor may develop at this stage or earlier.

Tanner stage 4: In stage 4, puberty is in full swing. Both boys and girls notice many visible and internal changes. 

Girls: Puberty begins after the age of 13 years. Changes include: 

• Breasts appear larger and fuller in shape.
• Pubic hair becomes thicker.
• Many girls get their first period between the ages of 12 and 14 years, but it can start earlier, especially if the body mass index is high.
• Height growth begins to slow down to about 2-3 inches per year.

Boys: Usually, puberty begins around the age of 14 years. Changes include: 

• The testicles, penis, and scrotum continue to grow and become bigger.
• Scrotum darkens in color.
• Armpit hair starts to grow.
• A deep voice becomes permanent. 
• Acne may appear on the face, back, or upper chest. 

Tanner stage 5: This final phase marks the end of physical maturation. 

Girls: Usually, puberty occurs around the age of 15 years. Changes include: 

• Breasts reach approximate adult size and shape, although breasts may change till the age of 18 years.
• Periods become regular after six months to two years of onset.
• Girls reach adult height; a minor increase may occur until 18 years.
• Pubic hair fills out, reaching the inner thighs.
• Reproductive organs and genitals are fully developed.
• Hips, thighs, and buttocks fill out in shape.

Boys: Usually, puberty starts around the age of 15 years, and most boys reach full growth by the age of 18 years. Changes include:

• Penis, testicles, and scrotum reach adult size.
• Pubic hair fills out, reaching the inner thighs.
• Facial hair starts growing, and some may need to shave.
• Growth in height slows down but continues.
• Muscles continue to grow.