- Hypothalamus acts as a coordinating center of the endocrine system because it sends a signal to the pituitary gland to produce hormones.
- Hormone derangements in hypothalamus-pituitary axis are associated with worsening of kidney function.
- A group of neurons in the hypothalamus is crucial for maintenance of blood sugar levels.
- Overactive hypothalamus and excessive production of hormone cortisol are common among patients with depression and other mood disorders.
- Hypothalamic neural stem cells decline over time. This decline speeds up the aging process.
The hypothalamus is a small brain region responsible for the production of many hormones which regulate sleep, body temperature, and other functions in a human body. The term hypothalamus derives from Greek and means under thalamus, which is exactly where it is located in the brain – under the thalamus. Although a small area, the hypothalamus is an integral part of the brain and it contains a control center for many functions of the autonomic nervous system and affects the endocrine system. Hypothalamus has a multitude of roles which will be discussed below.
The hypothalamus is one of the most important parts of the brain, involved in many kinds of motivation, among other functions. The hypothalamus controls the “Four F’s”: fighting, fleeing, feeding, and mating.
~ Marvin Dunnette
Hypothalamus hormone table
Hypothalamus is located the base of a human brain, below the thalamus and above the optic chiasm (part of the brain where optic nerves cross) and the pituitary gland. Although the pituitary gland is considered as the master gland of the body, the hypothalamus plays a major role in its functioning.
Hypothalamus acts as a coordinating center of the endocrine system because it sends a signal to the pituitary gland to produce hormones. The hypothalamic-pituitary axis has a direct impact on the adrenal gland, thyroid, gonads, and it influences growth, water balance, and milk production. Pituitary hormones secreted by the hypothalamus are listed below . 1
|Area of the Hypothalamus||Hormone||Target Organs||Function|
|Growth hormone (GH)||Adipose tissue, liver||Supports growth of body tissues|
|Prolactin||Mammary gland||Milk production|
|Luteinizing hormone (LH)||Testis and ovary||Control of reproductive function|
|Thyroid-stimulating hormone (TSH)||Thyroid||Secretion of thyroid hormones|
|Adrenocorticotropic hormone (ACTH)||Adrenal
|Secretion of glucocorticoids (steroid hormones)|
|Follicle-stimulating hormone (FSH)||Testis and
|Control of reproductive function|
|Milk ejection, uterine contractions|
|Anti-diuretic hormone (ADH)||Kidney||Body water conservation|
|Melanocyte-stimulating hormone||Skin||Stimulates melanin formation in melanocytes|
What does the hypothalamus do?
Hypothalamus works as a connector or mediator between endocrine and nervous systems. This explains why it participates in many processes that occur in our body. Below, you can see the rundown of functions where hypothalamus plays a role.
Thirst center in the brain located in hypothalamus
Everybody gets thirsty, but it is a little-known fact that thirst center is located in the hypothalamus. Special sensors in hypothalamus monitor the body’s concentration of sodium and other substances. In addition, hypothalamus receives inputs from sensors in the blood vessels that monitor blood volume and pressure. When sodium concentration increases or blood volume and pressure experience changes, the hypothalamus sends signals that make you thirsty . 2 Research shows that hypothalamus has two distinct populations of neurons that control thirst in two opposite directions (inducing thirst and suppressing it). 3
The main role of the thyroid is to regulate the metabolism. This butterfly-shaped gland is regulated by the hypothalamus and the pituitary gland. In fact, the hypothalamus-pituitary-thyroid axis (HPT axis) is a unique part of the neuroendocrine system which helps control metabolism and determines the set point for the production of thyroid hormone. 4 When thyroid levels decline, the hypothalamus starts to secrete thyrotropin-releasing hormone (TRH) which sends a signal to the pituitary to produce TSH. 5 As a result, thyroid secretes its hormones.
Hypothalamus and memory
Hypothalamus also takes part in the memory process through one of its nuclei called the mammillary nucleus. Due to its connection with the hippocampus, 6 this nucleus is associated with memory. One research also showed that a deep brain stimulation of hypothalamus evoked autobiographic memories or déjà vu in an obese patient when scientists were trying to identify potential appetite suppressant sites. 7
Hypothalamus and taste
Evidence shows that lateral hypothalamus (LH) regulates feeding behavior and taste processing although the latter is still poorly understood. Taste-specific LH neurons fall into two main subtypes of responses: affinity and aversions. Even though neurons that produce both types of responses are found in the same hypothalamus region, they may participate in distinct functional networks. 8 This means that lateral hypothalamus plays a crucial role in your taste aversions and preferences.
Hypothalamus and hunger
A key brain area that is involved in regulation of ingestive behavior is hypothalamus. In this part of your brain, a multitude of neuropeptides regulate appetite. 9 As mentioned above, lateral hypothalamus controls feeding behavior, but other regions take part in this function too. Ventromedial hypothalamus interacts with LH and has an influence on hunger motivation or feeling of fullness. Inconsistencies with VH action could be one of many mechanisms behind overweight/obesity 10 as it doesn’t send a signal that person isn’t hungry anymore.
Hypothalamus and menopause
Menopause is associated with lower levels of estrogen which causes numerous symptoms that women experience. The brain controls the release of estrogen through the hypothalamus-pituitary-gonadal axis and. Your brain also responds to estrogen levels in the body. Although hypothalamus initiates the neuroendocrine functions, the circuits that respond to estrogens also extend to the hippocampus, and other areas. 11
One study found that hormone secretion patterns in older women demonstrate major alterations of hypothalamic-pituitary feedback mechanisms together with decreased ovarian function. Aging women experience hypothalamic-pituitary insensitivity to estrogen which is manifested through both positive and negative feedback mechanisms. Essentially, menopause is linked with decreased expression of estrogen receptor in hypothalamic areas, 12 but more research is necessary to elucidate this topic.
Hypothalamus and sleep & yawning
Sleep is one of many functions regulated by the hypothalamus. Some studies show that posterior hypothalamus is the wakefulness center. In addition, the ventrolateral nucleus, a small area of the hypothalamus, is particularly involved in the switch between sleep and wakefulness. Neurons in this area promote sleep by inhibiting activity in brainstem areas that maintain wakefulness and a group of neurons in this region are specifically activated when you sleep. 13
Not only does hypothalamus regulate sleep and wakefulness, but its effects also extend to yawning. The paraventricular nucleus in hypothalamus contains cell bodies of oxytocinergic neurons (produce oxytocin) projecting to brain areas outside hypothalamus that also play a role in the expression of yawning. 14
Hypothalamus and sweating
Two types of glands are associated with sweating: eccrine (account for the most of sweat glands you have) and apocrine glands (found primarily in your armpits). Sweating is a part of thermogenesis and it usually occurs when sweat glands that are stimulated by the sympathetic nervous system to control temperature, get a signal from the hypothalamus to start cooling themselves off by producing sweat. One study found that changes in skin temperature shift the hypothalamic set-point temperature at which sweating begins. 15
Hypothalamus and kidney function
As seen above in the table with hormones secreted by the hypothalamus, anti-diuretic hormone targets kidneys and takes part in body water reabsorption. That is why this tiny area of your brain regulates health and functioning of the kidneys. Research shows that hormone derangements in hypothalamus-pituitary axis are associated with worsening of kidney function. As a result, the imbalance in the production of these hormones is implicated in the genesis of chronic kidney disease. 16
Hypothalamus and menstrual cycle
Menstrual cycle involves the synergistic function of pituitary, hypothalamus, ovaries, and the endometrium. Hypothalamus is the one that initiates the beat for the menstrual cycle through secretion of gonadotropin-releasing hormone (GnRH) which stimulates the pituitary to secrete luteinizing hormone and FSH. Then, the pituitary translates tempo set by hypothalamus into a signal, production of the above-mentioned hormones, that ovarian follicles interpret easily. Production of estrogen causes positive feedback by the hypothalamus and raises levels of LH and GnRH. This marks the process of ovulation where hormone progesterone is secreted. The role of this hormone is to prepare the endometrium for possible implantation of an embryo. 17 This is a standard process that culminates with a monthly period. Essentially, the entire process starts in your hypothalamus which induces chains of effects.
Hypothalamus and blood sugar
Evidence shows that a group of neurons in the hypothalamus is crucial for maintenance of blood sugar levels. When a team of scientists used a special technique on mice to switch these neurons on, blood glucose increased while insulin decreased, and animals ate more. On the other hand, when they switched off these neurons results were the opposite and blood glucose levels reduced. 18 These findings debunk the belief that blood glucose is under control of pancreas only and show that hypothalamus plays a major role too.
Hypothalamus and low testosterone
Testosterone is crucial for the sexual and reproductive health of every man, but it also participates in many processes in the body. As men age, levels of this hormone decline, but many other factors accelerate this process. We can categorize hypogonadism to primary and secondary. The latter indicates a problem in the hypothalamus or the pituitary gland. Hypothalamus produces the GnRH which signals the pituitary to make FSH and LH. In turn, LH signals testes to produce testosterone. 19 Irregularities with either hypothalamus or pituitary can affect testosterone production. Low testosterone can also be a result of the Kallmann syndrome, a condition associated with abnormal function of the hypothalamus and deficiency in GnRH. 20
Hypothalamus also takes part in male puberty and reproduction through activation of the hypothalamus-pituitary-gonadal axis which increases levels of LH, FSH, and sex hormones. 21
Hypothalamus and fight or flight
The fight or flight stress response starts in your brain. Stressful stimuli send the information to the amygdala, a brain region that takes part in emotional processing. When amygdala perceives the danger, it sends a signal to the hypothalamus, which acts as a command center. Hypothalamus activates the sympathetic nervous system and the adrenal-cortical system. The first uses nerve pathways to initiate reactions in the body while the latter uses bloodstream. Combination of these two effects creates fight or flight response. 22
Hypothalamus and depression
A growing body of evidence confirms that activation of HPA axis is common in depressed patients. Essentially, overactive hypothalamus and excessive production of hormone cortisol are common among patients with depression and other mood disorders. It is theorized that activation of HPA axis could be associated with structural changes in components of the axis. 23
Hypothalamus and homeostasis
The primary function of the hypothalamus is the maintenance of the body’s internal balance of homeostasis. What is homeostasis, actually? It comes from Greek words for same and steady and refers to any process that living beings use to actively maintain stable conditions necessary for survival. Evidence shows that interaction between positive and negative feedback loops in the hypothalamus-pituitary-adrenal system contributes to the regulation of homeostasis. 24
Hypothalamus and regulation of body temperature
Hypothalamus is crucial for regulation of body temperature. Certain neurons are sensitive to changes in local preoptic (area of the hypothalamus) temperature. In addition, these neurons also receive input from peripheral thermoreceptors and thus control multiple thermoregulatory processes. Warming of the preoptic area intensifies the firing rate in warm-sensitive neurons and induce sweating and panting which are heat loss responses. Cooling of the preoptic area enhances firing rate in cold-sensitive neurons and leads to heat retention and production. 25
Hypothalamus and weight loss
Although evidence on this subject are limited, hypothalamus could play a role in weight loss. As mentioned above, this is the area of the brain that regulates hunger and body temperature, both of which are necessary for successful weight loss. One study showed that low-frequency deep brain stimulation of hypothalamus helped the patient lose 6% of body weight over five months without any changes in diet and exercise. 26
Hypothalamus and aging
Aging is yet another process that hypothalamus regulates. Research shows that the number of hypothalamic neural stem cells decline over time. This decline speeds up the aging process. The effects of this loss aren’t irreversible. It’s entirely possible to slow and reverse various aspects of aging by replenishing stem cells or molecules they produce. Hypothalamic stem cells could exhibit their anti-aging effects by releasing molecules called microRNAs. 27
Hypothalamus is a brain area that despite being small regulates and participates in many processes in a human body. This brain region performs both endocrine and neural functions and although scientists have been investigating it for many years, there’s still a lot to learn about hypothalamus. One thing is for sure, the activity of hypothalamus and its stimulation are necessary for good health and wellbeing.
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