Precocious Puberty

Precocious Puberty

Precocious puberty is the onset of pubertal development at an unusually early age. In the UK, this is defined as the appearance of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. A full and accurate assessment is essential to determine the cause, as this can range from a normal variant to a serious underlying medical condition.

 

Classification

Precocious puberty is classified based on its aetiology and the hormone pathway involved.

  1. Central (GnRH-dependent) Precocious Puberty: This is the most common form and is caused by the premature activation of the hypothalamic-pituitary-gonadal (HPG) axis.

    • Idiopathic: The most frequent cause, especially in girls, with no underlying pathology identified.

    • Central Nervous System (CNS) Pathology: In boys, a CNS lesion (e.g., a hamartoma or a tumour) is a common cause.

  2. Peripheral (GnRH-independent) Precocious Puberty: This is caused by the release of sex hormones from a source other than the pituitary-gonadal axis.

    • Adrenal Disorders: Adrenal tumours or Congenital Adrenal Hyperplasia (CAH) can cause the premature production of androgens.

    • Gonadal Tumours: Ovarian or testicular tumours can produce sex hormones.

    • Exogenous Hormones: Accidental ingestion of sex hormones or exposure to environmental chemicals.

  3. Incomplete Precocious Puberty: This is a benign, self-limiting condition where a child shows isolated signs of puberty without full progression.

    • Isolated Thelarche: Premature breast development in girls.

    • Isolated Adrenarche: Early pubic hair development.

 

Clinical Assessment

History

  • Onset and Progression: Determine the age of onset and the rate of progression of pubertal signs.

  • Associated Symptoms: Ask about headaches, visual changes, or other neurological symptoms that might suggest a CNS tumour.

  • Family History: A family history of early puberty is common in idiopathic cases.

 

Examination

  • Accurate Measurements: Plot height and weight on a growth chart to assess the acceleration of growth.

  • Tanner Staging: Use Tanner staging to assess the extent of pubertal development. In boys, a testicular volume of 4 ml or more is a key sign of puberty.

  • Systemic Exam: Perform a full systemic examination to look for any signs of an underlying condition.

 

Investigations

  • First-line:

    • Bone Age: An X-ray of the left wrist is essential. A significantly advanced bone age confirms true precocious puberty.

    • Endocrine Bloods: Baseline blood tests should include LH, FSH, and sex hormones (oestradiol in girls, testosterone in boys).

  • Confirmatory Tests:

    • GnRH Stimulation Test: This is the gold standard for differentiating between central and peripheral precocious puberty.

    • Ultrasound: A pelvic ultrasound in girls can assess for ovarian cysts or tumours.

    • MRI Brain: An MRI of the brain is recommended for all boys with central precocious puberty and in girls with atypical or rapid progression to rule out a CNS lesion.

  • Other: An abdominal ultrasound may be needed if an adrenal tumour is suspected.

 

Management

  • Central Precocious Puberty: The goal is to stop the pubertal progression and preserve adult height potential. This is typically managed with GnRH analogues, which act as a ‘pubertal brake’ until the appropriate age.

  • Peripheral Precocious Puberty: Management is directed at treating the underlying cause, such as surgery for a tumour.

  • Incomplete Precocious Puberty: These children do not require treatment but should be monitored for any signs of progression to true precocious puberty.