Hypothalamus

What is the hypothalamus?

The hypothalamus is a structure deep within your brain. It’s the main link between your endocrine system and your nervous system. Your hypothalamus keeps your body balanced in a stable state called homeostasis.

What does your hypothalamus do?

Your hypothalamus receives chemical messages from nerve cells in your brain and from nerve cells in your body (your peripheral nervous system), which is also responding to signals outside your body.

Your hypothalamus’s main function is to react to these messages to keep your body in a stable state or internal balance. Just like you may have a “smart control” system to seamlessly manage all functions in your home, your hypothalamus is your body’s “smart control” coordinating center. Your hypothalamus helps manage your:

• Body temperature.
• Blood pressure.
• Hunger and thirst.
• Sense of fullness when eating.
• Mood.
• Sex drive.
• Sleep.

Your hypothalamus performs many of its “body balancing” jobs either by directly influencing the autonomic nervous system or by managing hormones. Your autonomic nervous system (bodily functions that work automatically) control several important functions, such as your heart rate and breathing (respiration).

Hormones are the “chemical messengers” that travel in your bloodstream to another part of your body. Hormones communicate either with another endocrine gland (which release other hormones) or with a specific organ.

Your hypothalamus:

• Makes some hormones itself that are stored elsewhere (in your posterior pituitary).
• Sends signals (hormones) to your pituitary gland, which either releases hormones that directly affect a part of your body or sends another signal (hormone) to a different gland in your body that then releases its hormone.

How does the hypothalamus interact with the pituitary gland?

Your pituitary gland sits just below your hypothalamus. It consists of two lobes, called the anterior pituitary and posterior pituitary. Your hypothalamus is connected to and communicates with your anterior lobe through a network of blood vessels. It communicates with your posterior lobe by tissue called the pituitary stalk.

Your hypothalamus sends signals in the form of releasing hormones to tell the anterior and posterior pituitary when to release (secrete) its hormones.

Anterior pituitary

This chart shows the hormones released by your hypothalamus to your anterior pituitary, the hormone the pituitary releases in turn and what the hormone does.

Posterior pituitary

Your hypothalamus makes two hormones but stores them in the posterior pituitary. When these hormones are needed, your hypothalamus sends a signal to the posterior pituitary to release them into the bloodstream. These two hormones are:

• Oxytocin: This hormone assists in the birthing process (stimulates uterine muscle contraction) and in lactation (release of breast milk). It’s also thought to play a role in human bonding, sexual arousal, trust, recognition, sleep cycle and feelings of well-being.
• Vasopressin: This hormone, also called antidiuretic hormone (ADH), regulates control of your body’s water/urine volume and blood pressure.

Other roles of the hypothalamus

Your hypothalamus also produces these hormones:

• Dopamine. Dopamine is the “feel-good” hormone. It gives you a sense of pleasure. It gives you the motivation to do something when you are feeling pleasure. Dopamine signals the pituitary to stop releasing prolactin.
• Somatostatin. This hormone prevents the secretion of several other hormones, including growth hormone, thyroid-stimulating hormone, cholecystokinin and insulin. In turn, all of these hormones control the production of somatostatin.

Your hypothalamus also corrects any imbalances in body temperature, stress and your daily bodily rhythms.

Where is the hypothalamus located?

Your hypothalamus, which is about the size of an almond, is located below the thalamus and above your pituitary gland. It sits directly above the brainstem at the base of your brain.

What happens if the hypothalamus is damaged?

When your hypothalamus is damaged, it doesn’t function as it should. Another term for when there’s a problem with your hypothalamus is hypothalamic dysfunction.

Causes of hypothalamic dysfunction include:

• Head injuries, such as a traumatic brain injury.
• Brain infection.
• Brain tumor in or around your hypothalamus or brain aneurysms.
• Significant weight loss caused by eating disorders, such as bulimia or anorexia.
• Brain surgery.
• Radiation therapy and chemotherapy.
• Birth defects involving the brain or hypothalamus.
• Inflammatory disease including multiple sclerosis and neurosarcoidosis.
• Some genetic disorders, such as growth hormone deficiency.

Hypothalamus dysfunction plays a role in:

• Hypothalamic-pituitary disorders: Because of the close interactions between your hypothalamus and pituitary gland, conditions that affect either are called hypothalamic-pituitary disorders. Certain hormone tests can help determine the exact hormone involved to make a more specific diagnosis.
• Hypopituitarism: This condition can be caused by damage to your pituitary gland or to your hypothalamus, which directly affects the pituitary gland.
• Diabetes insipidus: This condition happens when your hypothalamus doesn’t produce and release enough vasopressin. This causes your kidneys to lose too much water and results in excessive peeing and thirst.
• Prader-Willi syndrome: This inherited disorder causes your hypothalamus not to recognize the sensation that you’re full when you’re eating. Without this sensation, you have a constant urge to eat and are at risk for obesity.
• Kallmann syndrome: This syndrome has a genetic link to hypothalamic disease, causing such hypothalamic problems in children as delayed or no puberty.
• Acromegaly and pituitary gigantism: These are rare disorders of growth due to excessive release of growth hormone from your pituitary gland.
• Syndrome of inappropriate antidiuretic hormone: This occurs when the antidiuretic hormone level is too high. Causes include stroke, hemorrhage, infection, trauma, cancer and certain medications.
• Central hypothyroidism: Central hypothyroidism is a rare disorder that occurs due to both hypothalamic and pituitary disorders. The most common cause is a pituitary tumor such as a pituitary adenoma.
• Functional hypothalamic amenorrhea: This condition is the absence of a period for more than three months in people assigned female at birth (AFAB) who previously had regular periods or more than six months in people AFAB who have irregular menstruation. The most common cause of this condition is hypothalamic dysfunction.
• Hyperprolactinemia: A decrease in dopamine levels cause an increase in prolactin levels. Causes include a tumor, damage to nerve cells in the hypothalamus and other causes.

What are the symptoms of hypothalamus dysfunction?

Symptoms of hypothalamus dysfunction correspond to the types of hormone involved and if the hormone level is too low or too high. Some symptoms of a hypothalamus problem may include:

• High blood pressure or low blood pressure.
• Water retention or dehydration.
• Weight loss or weight gain with or without changes in appetite.
• Infertility.
• Poor bone health.
• Delayed puberty.
• Muscle loss and weakness.
• Body temperature fluctuations.
• Trouble sleeping (insomnia).
• Frequent need to pee.