Last updated:
6/23/2025
Years published: 2021, 2025
NORD gratefully acknowledges Shana E. McCormack, MD, MTR, Scientific Director, Neuroendocrine Center in the Division of Endocrinology and Diabetes, Children’s Hospital of Philadelphia & Associate Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania; M. Jennifer Abuzzahab, MD, Pediatric Endocrinologist, McNeely Pediatric Diabetes Center and Endocrine Clinic, Children’s Minnesota; Ashley H. Shoemaker, MD, MSCI, Associate Professor of Pediatrics, Vanderbilt University Medical Center; and Christian L. Roth, MD, Professor, Seattle Children’s Hospital, for the preparation of this report.
Summary
“Hypothalamic obesity” refers to excess weight gain that may follow from an injury to the hypothalamus, a brain region with many important functions including energy balance, temperature and autonomic nervous system regulation, modulation of sleep and daily (circadian) rhythm and controlling pituitary hormones. Hypothalamic obesity can be part of “hypothalamic syndrome”, a collection of symptoms from hypothalamic injury reflecting the many varied functions of the hypothalamus.
The hypothalamus helps regulate both energy intake (how much a person eats) and energy expenditure (how many calories are burned). When the hypothalamus is injured, the delicate balance between how much energy a person takes in and how much they burn is disrupted.
This imbalance can result in increased appetite, reduced energy use, or both, leading to rapid and significant weight gain. Some people may have excessive hunger (hyperphagia) and find it difficult to feel satiated (full). Others may gain weight even with reduced calorie intake due to a very low resting metabolic rate, meaning their body uses fewer calories at rest. People may also become less physically active, which can further contribute to weight gain.
The term “hypothalamic obesity” typically refers to obesity caused by structural injury to the hypothalamus. This may occur as a complication of brain tumor surgery, or due to tumors such as craniopharyngiomas, germinomas, gliomas, hamartomas and pituitary adenomas.¹ Other possible causes include traumatic brain injury (head traumas), infections, inflammatory conditions, radiation therapy, or bleeding in the brain.
These differences in how the body regulates weight distinguish hypothalamic obesity from more common forms of obesity.
Additionally, damage to the hypothalamus often affects other body systems, as the hypothalamus controls the pituitary gland, a gland responsible for producing many hormones. Common related health issues include hormonal deficiencies (hypopituitarism) requiring long-term hormone replacement therapy, imbalances in fluids and electrolytes, often due to vasopressin deficiency (previously known as central diabetes insipidus), sleep disturbances, temperature dysregulation, and problems with blood pressure and heart rate control, vision problems if the optic nerves are involved, and emotional, behavioral, and psychological challenges, which may also affect the individual’s family.
At present, there are no FDA-approved treatments specifically for hypothalamic obesity. However, several potential therapies are being studied in clinical trials.
A comprehensive management plan may include a special nutritional support and diet, physical activity programs and exercises, behavioral and psychological therapy, medication, and for some people, bariatric or other surgical options to lose weight.
Because responses to treatment can vary greatly, care is best provided by a multidisciplinary team experienced in managing complex metabolic and endocrine conditions. Emotional support and mental health resources are also essential to help individuals live well with hypothalamic obesity.
Some individuals may be born with genetic disorders (e.g., Prader-Willi syndrome) or brain malformations that affect hypothalamic function and also lead to obesity. These conditions demonstrate the critical role of the hypothalamus in regulating metabolism. However, the focus of this report is on acquired hypothalamic obesity that is obesity that develops after a hypothalamic injury occurs.
Introduction
Some of the earliest understanding of the role of the hypothalamus in weight regulation came from studies of individuals with hypothalamic tumors.² In 1900, Dr. Joseph Babinski,³ and in 1901, Dr. Alfred Froehlich,⁴ described patients who experienced both obesity and a failure to go through puberty. In 1904, Dr. Paul Ehrlich proposed that these symptoms were due to damage to the hypothalamus, not the pituitary.²
In the past, this condition was called Froehlich syndrome or sometimes these terms are used interchangeably. However, Froehlich syndrome can be considered as a form of acquired hypothalamic obesity, representing a more “classic” presentation, marked by delayed puberty and growth in children and adolescents with hypothalamic tumors. In contrast, acquired hypothalamic obesity encompasses a broader, more complex condition that affects people of any age and includes not only metabolic and hormonal dysfunction but also neurological, behavioral, and autonomic problems.
Note that NORD maintains a report on Froehlich syndrome because it may still be used as a clinical diagnosis. However, the term is now largely outdated in modern practice. When addressing cases involving obesity and hypogonadism, it is generally more appropriate to use precise terminology, either by identifying the underlying cause, when known, or by describing the specific hormonal abnormalities involved.
The key clinical feature of acquired hypothalamic obesity is excess weight gain following injury to the hypothalamus. The patient’s clinical presentation depends on the cause of the injury. For individuals with hypothalamic obesity related to brain tumors, a minority have obesity at the time they are diagnosed with the brain tumor, suggesting that the brain tumor has already caused injury leading to weight gain that is unfortunately likely to be persistent.5 More often, weight gain occurs after the tumor is removed surgically, suggesting a side effect of traditional surgical approaches is hypothalamic obesity and excess weight gain.6 Newer, less invasive surgical techniques, including endoscopic endonasal techniques (approaching the tumor through the nose) may be less likely to cause hypothalamic damage that leads to obesity.7,8 Increasingly, radiation is used as first line therapy, or in conjunction with subtotal tumor resection. Hypothalamic injury can still occur, but the symptoms may be delayed and occur months to years after radiation. For individuals with hypothalamic injury from other causes, for example, traumatic brain injury or inflammation, the weight gain tends to begin at the time of the injury or very shortly after the acute problem has been treated.
The most common concern expressed by individuals with hypothalamic obesity is how resistant the weight gain is to conventional approaches to weight management, such as healthy nutrition, caloric restriction and exercise. Another frequent observation is that individuals with hypothalamic obesity use less energy, both at rest9,10 and/or with physical activity and exercise.11 Because their bodies use less energy, individuals find that they can continue to gain weight even when caloric intake is restricted. Some, but not all, individuals also have a severe disorder of appetite regulation called hyperphagia, or excess appetite, and rarely feel satisfied after meals.12 These abnormal eating behaviors are often distressing to individuals and families and further contribute to weight gain. The hypothalamus also regulates other body functions that, when disrupted, cause symptoms. For example, individuals can have difficulty initiating and sustaining sleep. They can have excess daytime sleepiness related to sleep impairment and problems maintaining circadian (day-night) alignment. Some individuals experience difficulties maintaining body temperature within typical range. Some also have challenges with regulating heart rate and blood pressure in response to the body’s needs. Individuals with hypothalamic hamartomas can have a particular kind of seizure called gelastic seizures. Tumors located in this area can also lead to damage of the optic nerves and chiasm, leading to visual impairment, including blindness. While hypothalamic and pituitary damage often leads to delayed puberty and hypogonadism, sometimes hypothalamic injury causes early puberty development, which first manifests as breast development in girls and testicular enlargement in boys. Often, individuals are affected by pituitary hormone deficiencies, most notably arginine vasopressin deficiency, formerly called central diabetes insipidus, which affects fluid balance. (See “Related Disorders” and “Clinical Testing and Work-up” sections below for additional details regarding hypopituitarism.)
The single most important cause of acquired hypothalamic obesity is injury to the parts of the hypothalamus that regulate energy balance. Magnetic resonance imaging (MRI) studies have found that damage in particular areas in the hypothalamus towards that back of the brain, including the mamillary bodies, predicts obesity after surgical resection of a brain tumor.13 Other risk factors for the development of future obesity include obesity at the time of treatment and in individuals with brain tumors, papilledema, or swelling in the back of the eye indicating high pressure around the brain, at time of initial diagnosis.5 Finally, children whose mothers had higher body mass index (BMI) at diagnosis were also at increased risk for future obesity, indicating that complex genetic and environmental factors can continue to contribute to weight gain even in hypothalamic forms of obesity.14
Multiple factors likely combine to cause excess weight gain after hypothalamic injury and individuals vary in the extent to which they experience these different phenomena.15 These factors include: decreased energy use (both at rest, and with activity), increased appetite and decreased sense of being full after meals, chronically high circulating levels of the energy-storing hormone insulin, potential resistance to the appetite-regulating hormone leptin, disordered sleep and circadian phase regulation, pituitary hormone deficiencies and psychosocial factors that influence healthful behaviors.16,17 The potential roles for disordered signaling by enteroendocrine hormones and/or neuropeptides that regulate energy balance (e.g., ghrelin, oxytocin) are the focus of investigation. Much remains to be learned from ongoing research.
The epidemiology of acquired forms hypothalamic obesity directly reflects the epidemiology of the underlying causes of hypothalamic injury and rates of associated obesity. Multiple hypothalamic/pituitary brain tumors can lead to hypothalamic obesity. In one registry study, individuals with craniopharyngioma accounted for the majority (62%) of the cohort. By some estimates, there are 0.5-2.5 new cases of craniopharyngioma per 1 million individuals per year.18,19 The adamantinomatous sub-type of craniopharyngioma presents typically at one of two times in life, childhood (ages 5-15y) or middle adulthood (45-60y), while the papillary sub-type occurs almost entirely in adults.20 The epidemiology of the other types of tumors and injuries that lead to hypothalamic obesity demonstrates that this condition can affect individuals at any age.
The diagnosis of hypothalamic obesity is suspected when excess weight gain occurs in the context of a hypothalamic injury, as suggested by brain imaging studies. The diagnosis is additionally supported when the timing of the injury coincides with the onset of brisk and recalcitrant weight gain. The presence of one or more hypothalamic/pituitary hormone deficits is also evidence of clinically relevant injury.21 These signals (evidence of hypothalamic injury by brain imaging, timing of weight gain related to the injury and frequently the presence of other hormone deficits) help distinguish acquired hypothalamic obesity from the more common non-syndromic obesity that occurs from a complex interaction of genetic and environmental risk factors.
Clinical Testing & Work-Up
Clinical testing in the setting of hypothalamic obesity includes evaluation for disorders related to potential associated hypothalamic/pituitary hormone deficiencies: arginine vasopressin deficiency (formerly called central diabetes insipidus), adrenal insufficiency (cortisol deficiency), hypothyroidism (thyroid hormone deficiency), growth hormone deficiency and hypogonadism (deficiency of estrogen and progesterone in females and testosterone in males).
Also, it is important that individuals be evaluated for the myriad potential downstream health effects of obesity, including metabolic dysfunction associated steatotic liver disease (MASH), type 2 diabetes mellitus, abnormal lipid profile, sleep-disordered breathing, pseudotumor cerebri syndrome, orthopedic problems and psychosocial/mental health disorders.22 These complications of obesity may occur at excess rates in individuals with hypothalamic obesity as compared to individuals with “common” obesity with similar body mass index (BMI).
At the time of this writing, there are no FDA approved therapies specifically for hypothalamic obesity, though multiple options are currently in clinical trials. Currently, treatment includes evaluation and treatment of the underlying condition and other health problems, as well as trying a variety of strategies to manage obesity, which historically has not been as responsive to available medications. However, the advent of newer, more effective drug treatments for multifactorial polygenic obesity, including glucagon-like peptide receptor 1 (GLP1R) agonists27 and combination GLP1R/glucose-dependent insulinotropic polypeptide receptor (GIPR) agonists has provided additional treatment options.28, 29
Hypothalamic obesity is most appropriately addressed by an experienced, well-coordinated, multi-disciplinary team that designs and implements an individualized treatment approach. This approach should take into consideration other medical problems that the patient has, as well as patient/family circumstances and preferences. Ongoing care for the cause of the injury can help minimize the risk or extent of further hypothalamic injury. For survivors of brain tumors, care includes regular imaging surveillance to ensure early detection of any tumor recurrence. Management of hypothalamic obesity is complex and includes optimization of pituitary hormone replacement, nutrition (often, lower- or controlled carbohydrate approaches and/or portion control are trialed), physical activity and exercise, mental and behavioral health interventions and sometimes weight loss medications and/or or metabolic/bariatric surgery.17 Overall, aside from surgery, the benefits, if any, of these interventions are modest and may not be experienced by all patients. Medications with some evidence for potential benefit in at least a sub-set of patients include stimulants, metformin and glucagon-like peptide 1 receptor (GLP1R) agonists23; the GLP1R agonist class of medications is growing, and includes agents already approved for multifactorial, polygenic adolescent and adult obesity.23,24 Some individuals with hypothalamic obesity seem to respond well to these agents, though responses vary and the expected side effects of nausea and vomiting may be difficult for some to tolerate.28,29 Other medications already approved for use in multifactorial, polygenic obesity are also often trialed in hypothalamic obesity with variable degrees of success. For some patients, metabolic/bariatric surgery is an alternative to consider that may be helpful. For all individuals, it is critical to support both the patient and family at diagnosis and over time, since hypothalamic obesity can have significant impact on function and quality of life.
Individuals with hypothalamic obesity may or may not benefit from newly developed treatments for multifactorial, polygenic obesity, and such treatments may pose unique risks in the setting of conditions like hypopituitarism. An important area of research is studying the effects of treatments already approved for obesity specifically in individuals with hypothalamic obesity, with particular emphasis on safety. Since hypothalamic obesity may have causes distinct from multifactorial, polygenic obesity, treatments that address, for example, other potential hypothalamic/pituitary hormone problems such as oxytocin deficiency25 or autonomic dysfunction26 may hold promise. Recently, a phase 2 study of setmelanotide, a melanocortin 4 receptor (MC4R) agonist acting on brain energy balance pathways, already approved for several genetic forms of obesity, demonstrated promising effects in acquired hypothalamic obesity30; a phase 3 trial is underway with results forthcoming. Current research is also focused on strategies to identify the most appropriate treatment approach for each individual, because individuals vary in their presentation and experience of hypothalamic obesity and also have different responses to treatments. Multiple metabolic processes contribute to hypothalamic obesity, so it is expected that a combination of treatments may be most effective. However, how best to combine existing and/or novel therapies is not yet known. Patients and families, in partnership with the research community, can help to address these important questions.
Information on current clinical trials is posted on the Internet at https://clinicaltrials.gov/ All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact:
https://www.centerwatch.com/
For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/
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