The hypothalamus is a small but important area in the center of the brain. It plays a key role in the production of hormones and helps stimulate many important processes in the body and is located in the brain, between the pituitary gland and the thalamus.
What are the functions of the hypothalamus?
The main function of the hypothalamus is to maintain the body in homeostasis as far as possible.
Homeostasis means a healthy and balanced body state. The body is always trying to achieve this balance. The sensation of hunger, for example, is the brain’s way of letting its owner know that it needs more nutrients to achieve homeostasis.
The hypothalamus acts as a connector between the endocrine and nervous systems to achieve this. It is involved in many essential functions of the body, such as
- Body temperature
- Thirst
- Appetite and weight control
- Emotions
- Sleep cycles
- Sexual desire
- Childbirth
- Blood pressure and heart rate
- Production of digestive juices
- Balance of body fluids
As the different systems and parts of the body send signals to the brain, they alert the hypothalamus to any imbalanced factors that need to be addressed. The hypothalamus then responds by releasing the appropriate hormones into the bloodstream to balance the body.
An example of this is the remarkable ability of the human being to maintain a constant internal temperature of around 36.5°
If the hypothalamus receives the signal that the internal temperature is too high, it will tell the body to sweat. If it receives the signal that the temperature is too cold, the body will create its own heat by shivering.
What parts is the hypothalamus divided into?
Anterior hypothalamic nucleus
This area is also called the supraoptic region. Its main nuclei are the supraoptic and paraventricular. There are also other smaller nuclei in the anterior region.
The supraoptic nucleus of the hypothalamus is closely connected with the paraventricular area and its vasopressin neurons have a regulatory role in fluid homeostasis and blood pressure regulation
The paraventricular nucleus of the hypothalamus (PVN) is one of the most important autonomic control centers in the brain, with neurons playing essential roles in the control of stress, metabolism, growth, reproduction, the immune system and other more traditional autonomic functions (gastrointestinal, renal and cardiovascular).
The nuclei of the anterior region are largely involved in the secretion of several hormones. Many of these hormones interact with the nearby pituitary to produce additional hormones.
Some of the most important hormones produced in the anterior region are
- Corticotropin-releasing hormone (CRH). CRH is involved in the body’s response to physical and emotional stress. It signals the pituitary gland to produce a hormone called adrenocorticotropic hormone (ACTH). ACTH triggers the production of cortisol, an important stress hormone.
- Thyrotropin-releasing hormone (TRH). TRH production stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH). TSH plays an important role in the function of many parts of the body, such as the heart, gastrointestinal tract and muscles.
- Gonadotropin-releasing hormone (GnRH). The production of GnRH causes the pituitary gland to produce important reproductive hormones, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
- Oxytocin. This hormone controls many important behaviors and emotions, such as sexual arousal, confidence, recognition and maternal behavior. It is also involved in some functions of the reproductive system, such as childbirth and lactation.
- Vasopressin. Also called antidiuretic hormone (ADH), this hormone regulates water levels in the body. When vasopressin is released, it signals the kidneys to absorb water.
- Somatostatin. Somatostatin prevents the pituitary gland from releasing certain hormones, including growth hormone and thyroid-stimulating hormone.
The anterior region of the hypothalamus also helps regulate body temperature through sweat. It also maintains circadian rhythms
These are physical and behavioral changes that occur on a daily cycle. For example, being awake during the day and sleeping at night is a circadian rhythm related to the presence or absence of light.
Tuberal region
This area is also called the tuberal region. Its main nuclei are the ventromedial and arcuate.
The ventromedial nucleus helps control appetite, while the arcuate nucleus is involved in the release of growth hormone releasing hormone (GHRH). GHRH stimulates the pituitary gland to produce growth hormone. This is responsible for the growth and development of the body.
Posterior hypothalamic nucleus
This area is also called the mammillary region. The posterior hypothalamic nucleus and the mammillary nuclei are its main nuclei.
The posterior hypothalamic nucleus helps regulate body temperature by triggering shivering and blocking sweat production.
The role of the mammillary nuclei is less clear. Researchers believe it is involved in memory function
Conditions associated with damage to the hypothalamus
When the hypothalamus does not function properly, it is called hypothalamic dysfunction.
Several things can cause hypothalamic dysfunction, including the following
- Head injuries
- Certain genetic disorders, such as growth hormone deficiency
- Birth defects affecting the brain or hypothalamus
- Tumors in or around the hypothalamus
- Eating disorders, such as anorexia or bulimia
- Autoimmune diseases
- Surgery affecting the brain
The hypothalamus can be affected by nutrition and exercise. If the body does not have enough energy, it goes into a state of stress and produces cortisol, which can dampen the activity of the hypothalamus and cause problems. The stress response can be caused by eating disorders leading to:
- Underweight
- Emotional stress
- Too much exercise
- Not eating enough calories
High stress, drugs such as cocaine, and eating too much saturated fats that cause inflammation can lead to hypothalamic dysfunction. The dysfunction can affect many other activities in the body.
Below we are going to describe some of the existing hypothalamic dysfunctions
Hypothalamic obesity
A lesion in the hypothalamus can cause eating problems. People who have hypothalamic obesity may have symptoms such as:
- Rapid weight gain
- Excessive weight gain
- Uncontrollable appetite
- Low metabolism
Functional Hypothalamic Amenorrhea
This condition is sometimes called secondary amenorrhea and occurs when the menstrual period disappears in women
When the body does not get enough energy from food, it can result in high cortisol levels. Cortisol dampens the hypothalamus-ovary connection, resulting in low amounts of hormones. This affects ovulation and results in missed periods.
Functional hypothalamic amenorrhea can also be caused by a brain tumor.
Central diabetes insipidus
This type of diabetes is a rare autoimmune disorder in which the immune system damages the hypothalamus. Parts of the hypothalamus release a hormone called antidiuretic hormone, or vasopressor, which helps the kidneys filter water and maintain hydration.
Damage to the hypothalamus results in a lack of antidiuretic hormone and causes frequent urination and thirst.
Kallman’s syndrome
Dysfunction of the hypothalamus can result in absent or delayed puberty and lack of sense of smell, as in Kallman syndrome
This is a genetic disease that causes problems in the hypothalamus. It involves an insufficiency of hormones that affect sexual development. Symptoms may include:
- Absent menstrual periods
- Undescended testicles
- Small penis
- Absent or small breasts
- Kidney problems
- Hearing problems
- Cleft lip
- Cleft palate
Syndrome of inadequate antidiuretic hormone secretion
This syndrome causes high levels of antidiuretic hormone and low levels of electrolytes. It is usually caused by a stroke, infection, or cancer that damages the hypothalamus. An excess of this hormone can cause low sodium levels and lead to:
- Weakness
- Vomiting
- Tiredness
- Headaches
- Difficulty thinking
Prader-Willi syndrome
This is a rare inherited disorder. It causes the hypothalamus to not register when someone is full after eating
People with Prader-Willi syndrome have a constant need to eat, which increases the risk of obesity. Other symptoms include a slower metabolism and decreased muscle mass
In addition, people with this syndrome may have:
- Intellectual disabilities
- Poor growth
- Small genitalia
- Obesity
- Behavioral problems
Treatment of hypothalamic disorders
Most hypothalamic disorders are treatable, but treatment depends on the cause and the disorder.
Treatments may include:
- Surgery or radiation for tumors
- Hormonal medication for hormone problems such as hypothyroidism
- Appetite suppressant medications for overeating problems
- Diet plans
- Medications for obesity such as metformin
