Years After Brain Tumor Treatment, a Young Woman’s Body Lost Its Ability to Stay Warm

Deep in the base of the brain, a structure barely larger than an almond quietly governs some of the most fundamental processes that keep a human body alive. The hypothalamus regulates hunger, thirst, sleep, hormone release, and, crucially, body temperature. When this tiny control center is damaged, the consequences can be subtle at first and then, years later, startlingly severe. A new case report published in Clinical Case Reports by Ayumi Nishimura and colleagues describes a young Japanese woman whose body temperature regulation unraveled nearly a decade after successful treatment of a brain tumor, offering a vivid reminder that the aftermath of cancer therapy can unfold on timescales that most follow-up protocols simply do not anticipate.

The story began when the patient was thirteen years old. She visited a local clinic complaining of fatigue and fever, and routine laboratory tests revealed two red flags that pointed away from an ordinary infection: hypothyroidism and abnormally elevated sodium levels in her blood, a condition known as hypernatremia. Both findings suggested a problem with the pituitary gland and the hormonal circuitry it controls. A cranial computed tomography scan then identified a mass in the suprasellar region, the anatomical neighborhood just above the pituitary where the optic chiasm, pituitary stalk, and hypothalamus are packed closely together. She was referred to a pediatric department for further evaluation.

Because the mass sat in a location where surgical biopsy carried a high risk of injuring surrounding brain structures, the medical team did not attempt to obtain tissue for histological examination. Instead, they relied on indirect evidence. Magnetic resonance imaging showed a suprasellar mass extending toward the third ventricle and the pineal region, involving the hypothalamus itself. In addition, the patient’s serum level of beta-human chorionic gonadotropin, a hormone sometimes secreted by certain germ cell tumors, was mildly elevated at 0.3 nanograms per milliliter. Taken together, the imaging findings and the tumor marker were sufficient for a clinical diagnosis of primary intracranial germinoma, a rare germ cell tumor that arises in the midline of the brain and is particularly common in children and adolescents. At the time of diagnosis, she already had panhypopituitarism, meaning near-total loss of pituitary hormone production, and central diabetes insipidus, a condition in which the brain fails to produce the hormone that allows the kidneys to conserve water.

Treatment followed a standard strategy for intracranial germinoma: chemotherapy using the CARE regimen, followed by whole-ventricular irradiation at a total dose of 23.4 Gy delivered in thirteen fractions. The response was excellent. Follow-up magnetic resonance imaging demonstrated marked tumor regression, and the beta-human chorionic gonadotropin level normalized to 0.1 nanograms per milliliter or below. Yet even before treatment, the tumor’s location had already left its signature on her thermoregulation. She suffered persistent hyperthermia, with body temperatures ranging from 37 to 38 degrees Celsius, despite the absence of any clinical or laboratory evidence of infection or inflammation. The team suspected that the tumor’s infiltration of the hypothalamus had disrupted the brain’s thermostat. Roughly one month after therapy ended, her temperature settled into a normal range of 36 to 37 degrees, and for several years she remained clinically stable, with only occasional mild temperature elevations during summer months.

The first sign that something deeper was wrong arrived eight years after the original diagnosis, when the patient was twenty-one. In February of that year, she presented with fatigue, abdominal pain, and poor oral intake. Laboratory tests revealed hyponatremia, a dangerously low blood sodium level of 131 milliequivalents per liter, along with hypoglycemia, a blood glucose of 66 milligrams per deciliter. Her body temperature on arrival was 34.5 degrees Celsius, well below the threshold of clinical hypothermia. Physicians initially interpreted the picture as a sick-day state triggering relative adrenal insufficiency, and they administered stress-dose steroids while admitting her for active external warming. Her symptoms improved and she was discharged after seven days. Notably, however, the serum cortisol level drawn at presentation, which became available only later, was actually elevated at 56.2 micrograms per deciliter, a detail that would prove important.

A year later, the pattern repeated with greater severity. In January, at twenty-two years of age, she arrived with fatigue and was found to be profoundly hypothermic at 33.3 degrees Celsius with a bradycardic heart rate of just 41 beats per minute. In March of the same year she was readmitted with fatigue and decreased responsiveness, her temperature at 35.2 degrees. Once again, stress-dose steroids failed to produce rapid improvement, and once again the later cortisol measurement came back elevated, this time at 42.1 micrograms per deciliter. Brain magnetic resonance imaging showed no tumor recurrence and no new lesions. Hypothermia in the 34-degree range persisted throughout her hospitalization, but with active external warming her general condition gradually recovered, and she was discharged on the eleventh day.

The clinical reasoning that followed is what makes this case instructive. Adrenal crisis, the most feared endocrine emergency in patients with pituitary dysfunction, was initially suspected during both hypothermic episodes. But two observations argued against it: the cortisol levels measured during the episodes were elevated rather than low, and steroid supplementation did not rapidly resolve the symptoms. Combined with the absence of tumor recurrence on imaging, these findings pointed the team toward a different diagnosis: delayed hypothalamic dysfunction, a recognized late complication of cranial radiotherapy that can emerge months to decades after treatment in a dose- and time-dependent manner. The hypothalamus, the report’s authors emphasize, is more radiosensitive than the pituitary gland and may suffer functional impairment even at relatively low radiation doses. The whole-ventricular irradiation this patient received at 23.4 Gy may therefore have contributed to the slow, delayed failure of her brain’s temperature control system.

The metabolic derangements that accompanied her hypothermic episodes also fit this explanation. Hyponatremia and hypoglycemia during such episodes are more plausibly attributable to hypothermia itself than to adrenal failure. Severe cold impairs hepatic gluconeogenesis, the liver’s production of glucose, and blunts the counterregulatory hormonal responses, including glucagon release and sympathetic nervous system activation, that normally defend blood sugar and blood pressure against stress. Reduced oral intake compounds the problem. In other words, the hypothermia was not merely a symptom; it was the primary engine of her clinical deterioration and impaired consciousness, driving the laboratory abnormalities that had initially misled her physicians toward a diagnosis of adrenal insufficiency.

What can be done for a patient whose internal thermostat has failed? The report notes that several pharmacological agents targeting neurotransmitter systems have shown benefit in select cases of hypothermia associated with hypothalamic dysfunction, but no established therapy exists and the supporting evidence remains limited. Active external warming therefore constitutes the mainstay of management, encompassing direct measures such as electric blankets and hot water bottles as well as environmental temperature control with heating devices. Acting on this understanding, the medical team recommended proactive thermal management during the winters when the patient was twenty-three and twenty-four: maintaining room temperature above 20 degrees Celsius, using an electric blanket, and consuming warm beverages as part of daily life. Since these measures were implemented, she has experienced no further episodes of clinical deterioration or decreased consciousness requiring hospitalization, a strikingly simple intervention with apparently decisive results.

The broader lesson of this case extends well beyond one patient. Intracranial germinomas are cured in the great majority of cases, and long-term survival is the expected outcome. But as childhood and adolescent brain tumor survivors live decades beyond their treatment, the late effects of therapy become the dominant medical challenge. Endocrine surveillance for growth hormone deficiency, hypogonadism, and adrenal insufficiency is standard practice, yet thermoregulatory capacity is rarely assessed systematically. This report suggests it should be. A hypothalamic thermostat damaged by tumor infiltration or by radiation may compensate quietly for years before failing, and the failure mode, recurrent profound hypothermia masquerading as adrenal crisis or sepsis, is easy to misdiagnose. For clinicians caring for long-term survivors of suprasellar and hypothalamic tumors, the message is concrete: follow-up should address not only endocrine function but also thermoregulatory function, and practical lifestyle guidance about cold exposure may prevent life-threatening complications years after apparently successful treatment. In an era when cancer survival is increasingly measured in decades, the hypothalamus, that small almond-shaped guardian of the body’s internal climate, deserves a permanent place on the list of structures to watch.

Subject of Research: Delayed hypothalamic thermoregulatory dysfunction causing recurrent hypothermia after treatment of a suprasellar germinoma

Article Title: Delayed Hypothalamic Dysfunction Presenting as Recurrent Hypothermia After Treatment of Suprasellar Germinoma: A Case Report

Article References: Nishimura, A., Kado, T., Fujisaka, S., Kato, M., & Ishiki, M. (2026). Delayed Hypothalamic Dysfunction Presenting as Recurrent Hypothermia After Treatment of Suprasellar Germinoma: A Case Report. Clinical Case Reports, 14(10), Article e73535. https://doi.org/10.1002/ccr3.73535

Image Credits: AI Generated

DOI: 10.1002/ccr3.73535

Keywords: hypothalamus, hypothermia, suprasellar germinoma, cranial radiotherapy, thermoregulation, late complications, pituitary dysfunction, brain tumor survivorship, cortisol, case report, endocrinology, radiation therapy