Central Precocious Puberty
A 6-year-old girl has had breast development for three months, followed by an adult type body odour. She has no headaches or visual complaints. Her height has crossed from the 50th to the 90th percentile over the past year. Examination shows Tanner stage 3 breasts, Tanner stage 2 pubic hair, and no café-au-lait macules. Basal LH is 2.4 IU/L and estradiol is elevated. What is the most likely underlying cause?
- A.Long-standing primary hypothyroidism
- B.Idiopathic central precocious pubertyCorrect
- C.Estrogen-secreting ovarian tumour
- D.Congenital adrenal hyperplasia
Explanation
This girl has gonadotropin dependent, or central, precocious puberty, evidenced by a pubertal basal LH together with breast development preceding pubic hair and an accelerated height velocity. In girls the overwhelming majority of central precocious puberty is idiopathic, with no identifiable central nervous system lesion, whereas in boys a much higher proportion is caused by intracranial pathology such as hypothalamic hamartoma, glioma, or the sequelae of cranial irradiation. The pathophysiology is premature reactivation of pulsatile GnRH secretion, which drives the normal pubertal sequence in the correct order but at the wrong age. The clinical importance lies in premature epiphyseal fusion from sex steroid exposure, which shortens adult height, and in the psychosocial impact on a young child. Evaluation begins with basal LH, and a pubertal value confirms central activation; if basal LH is prepubertal, a GnRH stimulation test is used to unmask central activation. Once central precocity is confirmed, brain MRI is performed in all boys and in girls younger than 6 years, and treatment is a depot GnRH analogue to suppress the axis. An estrogen secreting ovarian tumour would suppress gonadotropins rather than raise LH and is usually palpable or visible on ultrasound. Congenital adrenal hyperplasia causes androgen excess with pubic hair and clitoromegaly rather than isolated estrogenization, and long-standing primary hypothyroidism causes precocity with delayed rather than advanced bone age.
Why each option
- A.
- Long-standing hypothyroidism can cause precocious puberty but classically with poor growth and a delayed bone age, the opposite of this child's growth acceleration.
- B.
- Correct. A pubertal basal LH with the normal breast then pubic hair sequence indicates central precocity, and in girls this is idiopathic in most cases.
- C.
- An estrogen-secreting ovarian tumour causes peripheral precocity with suppressed LH and FSH and is usually detectable on pelvic imaging.
- D.
- Congenital adrenal hyperplasia produces androgen excess with pubarche and clitoromegaly, not estrogen driven breast development with a pubertal LH.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024, Disorders of Pubertal Development
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