What causes hypothalamic obesity?

The hypothalamus is a small but very important part of the brain. Roughly the size of an almond and located just above the brainstem (the part of the brain that connects to the spinal cord), the hypothalamus contains groups of neurons (nerve cells) with specialized functions. Body temperature, sleep-wake cycles, circadian rhythms (the body's internal clock), hormone production, thirst, hunger, and metabolism are all regulated by the hypothalamus.

Because it coordinates many functions between different systems, the hypothalamus is sometimes described as the body's "control center."

Given how important the hypothalamus is to the normal functioning of the human body, it's unsurprising that injuries, illness, and diseases that affect the hypothalamus can have a serious impact on a person's health. One example is hypothalamic obesity.

Obesity is a medical condition characterized by excess amounts of adipose tissue (fat tissue) that result in a body mass index (BMI) of 30 or greater. One of the main causes is consuming more calories than the body requires for energy—though there are many factors that can influence obesity, including genetics, coexisting medical conditions, medications, and external factors (like access to food, where a person grew up, and where they live). In other words, the causes of obesity are often complex and can vary from person to person.

What is hypothalamic obesity?

Hypothalamic obesity occurs as a direct result of damage to the hypothalamus. Mentioned above, the hypothalamus regulates multiple processes within the body. Damage to the hypothalamus can disrupt several processes that help the body maintain a healthy weight.

Hunger and satiety (fullness) signals

Like many processes in the body, hunger and fullness are regulated by hormones, or chemical messengers. For example, the hormone leptin, which triggers a satiety signal when the stomach is full. Damage to the hypothalamus can disrupt the brain’s ability to interpret these signals. As a result, a person can experience extreme and overwhelming hunger that can lead to overeating and contribute to weight gain.

Lowered metabolic rate

Metabolism is the process of the body turning food into substances that can be used for energy and building new cells. Metabolic rate refers to the speed at which the body uses energy—in other words, it is how quickly your body uses calories (units of energy contained within food and stored in adipose tissue). Damage to the hypothalamus can slow down metabolic rate. This means that the body is using less energy, which will contribute to weight gain and make it more difficult to lose weight.

Pituitary gland dysfunction

Damage to the hypothalamus also affects the pituitary gland, a hormone-producing gland that sits below the hypothalamus. This can result in low levels of growth hormone, imbalances of cortisol, and low levels of thyroid-stimulating hormone. These hormone imbalances can contribute to weight gain.

What can damage the hypothalamus?

While all cases of hypothalamic obesity are the result of damage to the hypothalamus, there are many circumstances that can lead to this damage:

• Tumors of the hypothalamus, pituitary gland, or brain stem
• Surgery, such as surgery to remove a tumor
• Traumatic brain injury (TBI)
• Radiation therapy used to treat brain tumors or head and neck cancers
• Infections, inflammation, and bleeding in the brain
• Genetic disorders that affect hypothalamic function

How is hypothalamic obesity treated?

Hypothalamic obesity can be challenging to treat, and it requires individualized care. A treatment plan should take into account and address the underlying cause of hypothalamic obesity, as well as complications and coexisting conditions.

There is no cure for hypothalamic obesity, and the goals of treatment are to manage and control the condition. Obesity treatments, including medications, diet, and exercise may be used, though these are often less effective at treating hypothalamic obesity (compared to more common forms of obesity). However, therapies for hypothalamic obesity are under development. Mental health and social support are also an important aspect of treatment.