[Pediatrics] What causes precocious puberty in girls?

Early puberty in girls—also known as precocious puberty—is defined as the onset of secondary sexual characteristics before age 8 years. This includes breast development (thelarche), pubic hair growth (pubarche), accelerated linear growth, and, in some cases, menarche. The underlying causes fall into two broad categories: central (gonadotropin-dependent) and peripheral (gonadotropin-independent) precocious puberty.

Central precocious puberty (CPP) is the most common form and results from premature activation of the hypothalamic–pituitary–gonadal (HPG) axis. In most cases—particularly in girls aged 6–8 years—the cause is idiopathic, meaning no structural abnormality or identifiable pathology is found. However, organic causes must be ruled out, especially in younger children (<6 years) or those with atypical features (e.g., rapid progression, neurological symptoms, or developmental delay). These may include hypothalamic hamartomas, optic pathway gliomas, cranial irradiation, traumatic brain injury, or inflammatory conditions such as sarcoidosis or encephalitis.

Peripheral precocious puberty (PPP) arises from sex hormone excess independent of HPG axis activation. Causes include ovarian cysts (often functional and self-limited), congenital adrenal hyperplasia (especially non-classic or late-onset forms), McCune–Albright syndrome (characterized by café-au-lait spots, polyostotic fibrous dysplasia, and endocrine hyperfunction), exogenous estrogen exposure (e.g., topical creams, herbal supplements, or contaminated food), and rare tumors such as granulosa cell tumors or adrenal carcinomas.

Comprehensive evaluation is essential and typically includes a detailed history (including growth trajectory, family history of early puberty, medication or supplement use, and psychosocial stressors), physical examination with Tanner staging, bone age assessment via left hand/wrist radiograph, and targeted laboratory testing—such as serum estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid function tests, and adrenal androgens. A GnRH stimulation test helps confirm central etiology, while pelvic ultrasound may identify ovarian or adrenal abnormalities. Brain MRI is indicated for suspected CNS pathology, particularly in children under age 6 or with neurologic signs.

Management depends on the underlying cause. Idiopathic CPP is often treated with gonadotropin-releasing hormone analogues (e.g., leuprolide or histrelin) to suppress puberty, preserve adult height potential, and mitigate psychosocial challenges. PPP requires treatment of the specific etiology—e.g., surgical resection of a tumor, glucocorticoid replacement in congenital adrenal hyperplasia, or discontinuation of exogenous hormones. Multidisciplinary care involving pediatric endocrinology, psychology, and sometimes neurology or oncology is critical for optimal outcomes.