Clinical scenario:
A 6-year-old girl is brought with progressive breast development and pubic hair over the past 8 months. Examination shows Tanner stage 3 breast development and Tanner stage 2 pubic hair. Her growth velocity has increased, and bone age is advanced by 2 years. Pelvic ultrasound shows an enlarged uterus and bilateral multicystic ovaries. Basal LH is elevated, and GnRH stimulation produces a pubertal LH response.
Which of the following is the most appropriate next investigation?
A. Adrenal computed tomography
B. Brain MRI with hypothalamic-pituitary protocol
C. Karyotype
D. Pelvic computed tomography
E. Serum estradiol
Correct answer & Explanation:
Answer: B. Brain MRI with hypothalamic-pituitary protocol
Explanation
The pubertal LH response to GnRH stimulation confirms central (gonadotropin-dependent) precocious puberty.
In a girl with confirmed central precocious puberty, particularly when presentation is before 6 years of age, brain MRI is indicated to exclude a hypothalamic-pituitary lesion such as a hypothalamic hamartoma, tumor, or other central nervous system pathology.
Serum estradiol may support the diagnosis but does not determine its cause. Adrenal imaging is more appropriate when there are features suggesting adrenal androgen excess, while pelvic imaging does not adequately evaluate the central causes.
The key exam sequence is:
Precocious puberty → confirm central activation with GnRH stimulation → investigate the CNS with brain MRI.
