To diagnose precocious puberty, the doctor will:

  • Review your child's and your family's medical history
  • Do a physical exam
  • Run blood tests to measure hormone levels

X-rays of your child's hand and wrist also are important for diagnosing precocious puberty. These X-rays can help the doctor determine your child's bone age, which shows if the bones are growing too quickly.

Determining the type of precocious puberty

Your child's doctor will also need to find out which type of precocious puberty your child has. To do so, he or she will perform a test called a gonadotropin-releasing hormone (Gn-RH) stimulation test, and then take a blood sample. In children with central precocious puberty, this hormone will cause other hormone levels to rise. In children with peripheral precocious puberty, other hormone levels stay the same.

Additional testing for central precocious puberty

  • Magnetic resonance imaging (MRI). A brain MRI is usually done for children who have central precocious puberty to see if any brain abnormalities are causing the early start of puberty.
  • Thyroid testing. The doctor may also test your child's thyroid if he or she shows any signs of slow thyroid function (hypothyroidism), such as fatigue, sluggishness, increased sensitivity to cold, constipation, a drop in school performance or pale, dry skin.

Additional testing for peripheral precocious puberty

Other tests also are necessary for children with peripheral precocious puberty to find the cause of their condition. For example, the doctor may run additional blood tests to check other hormone levels or, in girls, he or she may do an ultrasound to check for an ovarian cyst or tumor.