Rare Brain Tumors in Young Girls Trigger Early Puberty and Hormone Clues Doctors Should Not Miss

A team of pediatric endocrinologists in Guangzhou, China, has described three young girls whose early breast development turned out to be the first visible sign of a hormone-secreting brain tumor. The report, published in Frontiers in Endocrinology by researchers at The First Affiliated Hospital of Sun Yat-sen University, brings together the clinical stories of three girls aged between five and six at disease onset, all of whom were eventually diagnosed with beta-human chorionic gonadotropin (β-hCG)-secreting intracranial germ cell tumors. The cases are notable because this tumor type almost never drives precocious puberty in girls, and because every one of them first showed a deceptively mundane symptom that parents and even clinicians can easily overlook: extreme thirst and urination.

The three children, treated at the hospital’s Department of Pediatric Endocrinology between 2020 and 2025, each began drinking and urinating excessively months before anyone sought medical help. One girl’s parents noticed the symptoms a full year before breast budding appeared; the others waited five months and seventeen months respectively. By the time they reached the clinic, all three had breast development, and laboratory testing revealed the two hallmarks that would define their illness: peripheral precocious puberty, in which sex hormones rise without activation of the brain’s master puberty switch, and arginine vasopressin deficiency, previously known as diabetes insipidus, in which the pituitary fails to produce the hormone that concentrates urine.

The diagnostic picture that emerged was strikingly consistent. Magnetic resonance imaging of the pituitary region revealed space-occupying lesions in or near the sella turcica, the bony cradle at the base of the brain where the pituitary gland sits. One girl had a suprasellar tumor measuring roughly 23 by 20 by 24 millimeters; another showed uniform thickening of the pituitary stalk about five millimeters wide; the third had a hypothalamic tumor of about 30 by 27 by 32 millimeters. Crucially, blood tests showed β-hCG concentrations of 5010.0, 314.3, and 202.8 milli-international units per milliliter, against a normal upper limit of less than 1.0. Cerebrospinal fluid samples carried the same marker at elevated levels in all three children.

β-hCG is a hormone best known for sustaining pregnancy, but certain tumors hijack the genes that produce it. Among intracranial germ cell tumors, which account for roughly 3 to 15 percent of primary pediatric brain tumors, choriocarcinomas, embryonal carcinomas, and immature teratomas secrete large amounts of the hormone, while germinomas typically release smaller quantities. Because β-hCG structurally mimics luteinizing hormone, it can switch on hormone production in the gonads. In boys, this effect is well documented: tumor-derived β-hCG activates receptors on testicular Leydig cells, driving testosterone output and triggering puberty that bypasses the hypothalamic-pituitary-gonadal axis entirely.

Girls, however, rarely respond the same way. Ovarian activation normally requires both luteinizing hormone and follicle-stimulating hormone working in concert, and β-hCG has only weak FSH-like activity. Classic work cited in the report suggests that a blood β-hCG concentration of 1000 milli-international units per milliliter is roughly equivalent to an FSH level of just 2 international units per liter. That mismatch helps explain why, before this series, only six girls with β-hCG-secreting intracranial germ cell tumors and precocious puberty had ever been reported in the medical literature, nearly all with tumors in the sellar region rather than the pineal region where boys’ tumors tend to arise.

The Guangzhou team argues that several mechanisms probably conspired in their patients. At supraphysiological concentrations, β-hCG may push enough FSH-like signal to matter. The hormone also shares its receptor with LH on ovarian theca cells, where sustained activation of the cAMP-PKA pathway upregulates steroidogenic enzymes such as CYP17A1, driving production of androstenedione and testosterone that aromatase can then convert into estrogens. Some tumor cells may even carry aromatase themselves: in a 2021 Japanese case, an intracranial choriocarcinoma from a girl with precocious puberty stained strongly for both hCG and aromatase, suggesting the tumor was directly manufacturing estrogen. Two of the three Chinese patients also had elevated prolactin, which fell after treatment, and the authors note that stalk compression can release lactotroph cells from dopaminergic inhibition while prolactin itself may heighten ovarian sensitivity to gonadotropins.

Treatment followed established pediatric protocols. Each girl received platinum-based chemotherapy, using cisplatin or carboplatin combined with etoposide, followed by ifosfamide and etoposide cycles, and then radiotherapy. The response was rapid and measurable. After just two chemotherapy cycles, breast and pubic hair development had regressed to Tanner stage I in all three children. β-hCG levels in blood and spinal fluid normalized within two to three cycles, MRI showed tumor shrinkage in every case, and estradiol and testosterone concentrations fell. Two of the girls required replacement hormones for multiple pituitary deficits, including hydrocortisone, desmopressin, and levothyroxine, and both showed complete tumor disappearance on follow-up imaging.

The recovery was not entirely straightforward, and the complications carry lessons of their own. One girl developed cerebral salt-wasting syndrome during treatment, with sodium dropping to 122 millimoles per liter, urinary sodium excretion climbing to 476 millimoles per day, and a fractional excretion of sodium of 33 percent, all reversed with fludrocortisone. Another experienced ifosfamide encephalopathy. Most consequentially, seven months after finishing radiotherapy, the first patient returned with renewed breast development and a growth spurt of 13 centimeters per year. Her GnRH stimulation test showed an LH peak of 15.04 international units per liter with an LH-to-FSH ratio of 1.2, bone age advanced five years’ worth in twelve months of calendar time, and she was diagnosed with rapidly progressive central precocious puberty, now treated with a GnRH agonist.

The authors interpret this late complication as a physiological rebound. While the tumor poured out β-hCG, the resulting estrogen suppressed the child’s own hypothalamic-pituitary-gonadal axis through negative feedback. Once treatment eliminated the tumor and its hormone, that suppression lifted abruptly, potentially unleashing the premature activation of the puberty center that defines central precocious puberty. This pattern, previously described after treatment of pineal germ cell tumors, argues for vigilant long-term endocrine surveillance after germ cell tumor therapy, with follow-up at least every six months covering growth, secondary sexual characteristics, hormone panels, and bone age.

The practical message for clinicians and parents is concrete. When a child of either sex presents with early puberty alongside signs of multiple pituitary failures, such as excessive thirst and urination from arginine vasopressin deficiency, or mass-effect symptoms like declining vision, the authors recommend routine measurement of serum β-hCG and alpha-fetoprotein together with contrast-enhanced sellar MRI to rule out organic lesions including germ cell tumors. The team acknowledges the limits of their work: the series is small, retrospective, and lacked biopsy confirmation, so the mechanistic explanations remain hypotheses drawn from prior literature. Even so, the pattern they describe, precocious puberty preceded by months of unexplained polyuria and polydipsia, may give physicians an earlier window into a rare but treatable tumor, before the hormone storm has done its work.

Subject of Research: β-hCG-secreting intracranial germ cell tumors presenting as precocious puberty and arginine vasopressin deficiency in girls

Article Title: Case Report: Intracranial germ cell tumors in girls presenting with peripheral precocious puberty and arginine vasopressin deficiency

Article References: Xin, W., Ma, H., Li, Y., Zhang, J., Guo, S., Zheng, R., Wang, B., Xiao, H., & Chen, Q. (2026). Case Report: Intracranial germ cell tumors in girls presenting with peripheral precocious puberty and arginine vasopressin deficiency. Frontiers in Endocrinology, 17, Article 1886797. https://doi.org/10.3389/fendo.2026.1886797

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1886797

Keywords: intracranial germ cell tumors, precocious puberty, beta-hCG, arginine vasopressin deficiency, diabetes insipidus, pediatric endocrinology, pituitary MRI, chemotherapy, radiotherapy, central precocious puberty, tumor markers, hypothalamus