Puberty starts when a part of the brain called the hypothalmus begins releasing a hormone called gonadotropin releasing hormone (GnRH).  GnRH then signals the pituitary gland to release two more hormones - luteinizing hormone (LH) and follicle-stimulating hormone (FSH) – to start sexual development.

A study funded in part by NICHD has identified a gene that appears to be the crucial signal for the beginning of puberty.  Without a functioning copy of the gene, known as GPR54, humans appear unable to enter puberty normally.

• In females:
  
  • The first sign of puberty is usually breast development. 
  • Other signs are the growth of hair in the pubic area and armpits, and acne.
  • Menstruation (or a period) usually happens last. 

• In males:
  
  • Puberty usually begins with the testicles and penis getting bigger. 
  • Then hair grows in the pubic area and armpits. 
  • Muscles grow, the voice deepens, and acne and facial hair develop as puberty continues.

Both boys and girls usually have a growth spurt (a rapid increase in height) that lasts for about 2 or 3 years along with the signs listed above.  This brings them closer to their adult height, which they reach after puberty.

• Some children may begin puberty earlier than normal, a condition called precocious puberty.  If signs of puberty occur early (before age 7 or 8 for girls and before age 9 for boys), parents and caregivers should talk to their child’s health care provider to see if treatment is needed.

• Other children may have delayed puberty, meaning the process begins later than normal. Sometimes there is a reason for puberty starting late; for example, many young girls who are gymnasts start puberty later than those who are not gymnasts.  But in many cases, there is no known reason for the delay.

If development is later than normal, parents and caregivers should talk to a health care provider, who can make sure there is not a medical condition causing the delay.  But most kids with delayed puberty need no treatment and begin puberty on their own body’s time.