The hypothalamus–pituitary complex can be thought of as the “command center” of the endocrine system.
Anterior and Posterior Pituitary Gland.
Image by TheVisualMD
Pituitary Gland
Woman's Brain Revealing Hypothalamus and Pituitary Gland
Image by TheVisualMD
Woman's Brain Revealing Hypothalamus and Pituitary Gland
Woman's Brain Revealing Pituitary Gland : The pituitary gland is a pea-sized endocrine gland located at the base of the skull, between the optic nerves. It is often referred to as the endocrine system's "master gland" because it regulates the activities of other glands. The pituitary, however, takes its orders from the hypothalamus, which decides which particular hormones the pituitary should release and when. The pituitary governs testosterone and estrogen production, as well as ovulation and breast milk production; it also helps regulate growth, blood pressure, maintain proper fluid balance, and other aspects of metabolism.
Image by TheVisualMD
Pituitary Gland
The hypothalamus–pituitary complex can be thought of as the “command center” of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus–pituitary complex coordinates the messages of the endocrine and nervous systems. In many cases, a stimulus received by the nervous system must pass through the hypothalamus–pituitary complex to be translated into hormones that can initiate a response.
The hypothalamus is a structure of the diencephalon of the brain located anterior and inferior to the thalamus. It has both neural and endocrine functions, producing and secreting many hormones. In addition, the hypothalamus is anatomically and functionally related to the pituitary gland (or hypophysis), a bean-sized organ suspended from it by a stem called the infundibulum (or pituitary stalk). The pituitary gland is cradled within the sellaturcica of the sphenoid bone of the skull. It consists of two lobes that arise from distinct parts of embryonic tissue: the posterior pituitary (neurohypophysis) is neural tissue, whereas the anterior pituitary (also known as the adenohypophysis) is glandular tissue that develops from the primitive digestive tract. The hormones secreted by the posterior and anterior pituitary, and the intermediate zone between the lobes are summarized in image.
Pituitary Hormones
Pituitary lobe
Associated hormones
Chemical class
Effect
Anterior
Growth hormone (GH)
Protein
Promotes growth of body tissues
Anterior
Prolactin (PRL)
Peptide
Promotes milk production from mammary glands
Anterior
Thyroid-stimulating hormone (TSH)
Glycoprotein
Stimulates thyroid hormone release from thyroid
Anterior
Adrenocorticotropic hormone (ACTH)
Peptide
Stimulates hormone release by adrenal cortex
Anterior
Follicle-stimulating hormone (FSH)
Glycoprotein
Stimulates gamete production in gonads
Anterior
Luteinizing hormone (LH)
Glycoprotein
Stimulates androgen production by gonads
Posterior
Antidiuretic hormone (ADH)
Peptide
Stimulates water reabsorption by kidneys
Posterior
Oxytocin
Peptide
Stimulates uterine contractions during childbirth
Intermediate zone
Melanocyte-stimulating hormone
Peptide
Stimulates melanin formation in melanocytes
Overview
The hypothalamus–pituitary complex is located in the diencephalon of the brain. The hypothalamus and the pituitary gland are connected by a structure called the infundibulum, which contains vasculature and nerve axons. The pituitary gland is divided into two distinct structures with different embryonic origins. The posterior lobe houses the axon terminals of hypothalamic neurons. It stores and releases into the bloodstream two hypothalamic hormones: oxytocin and antidiuretic hormone (ADH). The anterior lobe is connected to the hypothalamus by vasculature in the infundibulum and produces and secretes six hormones. Their secretion is regulated, however, by releasing and inhibiting hormones from the hypothalamus. The six anterior pituitary hormones are: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).
Source: CNX OpenStax
Additional Materials (28)
Anterior and Posterior Pituitary Gland.
Anterior and Posterior Pituitary Gland.
Image by TheVisualMD
Posterior Pituitary
Neurosecretory cells in the hypothalamus release oxytocin (OT) or ADH into the posterior lobe of the pituitary gland. These hormones are stored or released into the blood via the capillary plexus.
Image by CNX Openstax
Anterior Pituitary
The anterior pituitary manufactures seven hormones. The hypothalamus produces separate hormones that stimulate or inhibit hormone production in the anterior pituitary. Hormones from the hypothalamus reach the anterior pituitary via the hypophyseal portal system.
Image by CNX Openstax
Pituitary Gland - Anterior and Posterior - Hormones
Video by 5MinuteSchool/YouTube
Endocrine System, Pituitary Gland
Video by Carpe Noctum/YouTube
Hypothalamus Control of the Anterior Pituitary Gland - Hypothalmic Control
The hypothalamic-pituitary-adrenal axis integrates and mediates the stress response to early life and later on adversity. The perception of real and/or presumed physical and social threats causes activation of the hypothalamic-pituitary-adrenal axis. Anxious states arise from activation of the amygdala and magnify the stress response via neuronal projections to the paraventricular nucleus (PVN). The hippocampus plays an important role in the assessment of stressors and as a site of glucocorticoid receptor (GR) mediated negative feedback regulation. Release of the hypothalamic neuropeptides corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP) promotes the synthesis and secretion of adrenocorticotrophin (ACTH), a posttranslational cleavage product of anterior pituitary pro-opiomelanocortin mRNA (POMC). ACTH in turn stimulates the release of glucocorticoids from the adrenal glands. These hormones circulate throughout the whole body and the brain and bind to intracellular nuclear steroid receptors. Hippocampal mineralocorticoid (MR) receptors act to the onset of the stress response, while GR at the hippocampus, PVN, and anterior pituitary terminates the stress response. The GR further transactivates FKBP51 encoding a chaperon protein which curtails GR activity through a fast intracellular negative feedback loop.
Image by Raabe FJ and Spengler D/Wikimedia
Hypothalamic–pituitary–gonadal axis in females
Hypothalamic–pituitary–gonadal axis in females, with estrogen exerting mainly negative feedback on follicle-stimulating hormone secretion from the pituitary gland.
Image by Lu Kong, Ting Zhang, Meng Tang and Dayong Wang
The pituitary gland is a pea-sized gland located at the base of the skull between the optic nerves. The pituitary gland secretes hormones. Hormones are chemicals that travel through our blood stream. The pituitary is sometimes referred to as the \"master gland\" as it controls hormone functions such as testosterone production in males and ovulation and estrogen production in females.
Image by TheVisualMD
HPA Axis
This figure describes the relationships between cortisol synthesis by the HPA axis and cortisol binding to hippocampal MR receptors with respect to synaptic firing at CA1 hippocampal neurons
Image by Mark T McAuley1 , Rose Anne Kenny2 , Thomas BL Kirkwood1 , Darren J Wilkinson3 , Janette JL Jones4 and Veronica M Miller
Pituitary gland
Diagram showing the position of the pituitary gland in the brain
Image by Cancer Research UK uploader
Pituitary gland
Pituitary gland rendered in 3D
Image by Life Science Databases(LSDB)
Depressed Female with Visible Pituitary Gland
he HPA axis is a complex set of interactions between the hypothalamus, the pituitary gland, and the adrenal gland. These interactions provide feedback loops for controlling the brain and body's reactions to stress. In normal functioning, environmental stress activates the hypothalamus to release corticotrophin releasing factor (CRF) which in turn stimulates the pituitary gland to increase production of adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal gland to release cortisol. It is cortisol that produces effects to help us deal with stress. In clinical depression, higher than normal levels of cortisol and CRF have been detected in cerebrospinal fluid.1-3 Treatment of depression with antidepressants or electroconvulsive therapy brings down the high levels of CRH.2,4
Image by TheVisualMD
Pituitary Gland
In normal functioning, environmental stress activates the hypothalamus to release corticotrophin releasing factor (CRF) which in turn stimulates the pituitary gland to increase production of adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal gland to release cortisol. It is cortisol that produces effects to help us deal with stress.
Image by TheVisualMD
Initimate Couple with visible Brain highlighting Pituitary
This image shows a couple engaged in an intimate exchange with partial brain anatomy visible, including the pituitary gland. The pituitary secretes oxytocin, also known as \"the love hormone.\" The image supports content explaining that oxytocin, released upon orgasm, can reduce pain and promote sleep
Image by TheVisualMD
Thyroxine, Free (FT4): Pituitary Gland
The pituitary gland is often referred to as the 'master gland' because it regulates the activities of other endocrine glands. The pituitary gland, however, takes its orders from the hypothalamus, which decides which particular hormones the pituitary should release and when.
Image by TheVisualMD
Thyroxine, Total (T4): Pituitary Gland
The pituitary is a pea-size gland attached to the base of the brain. It is often referred to as the \"master gland\" because it regulates the activities of other endocrine glands. The pituitary, however, takes its orders from the hypothalamus, an area of the brain that sits above the pituitary and is connected to it by neurons. The hypothalamus decides which particular hormones the pituitary should release and when.
Image by TheVisualMD
Drawing of a body torso showing the brain, with the pituitary gland; the thyroid, with the 4 parathyroid glands; and the pancreas, with a detail of the pancreatic islets
In MEN1, the overactive glands may include the parathyroids, pancreas, or pituitary.
Image by NIDDK Image Library
Positive Feedback- Childbirth
Positive feedback is the amplification of a body’s response to a stimulus. For example, in childbirth, when the head of the fetus pushes up against the cervix (1) it stimulates a nerve impulse from the cervix to the brain (2). When the brain is notified, it signals the pituitary gland to release a hormone called Oxytocin (3). Oxytocin is then carried via the bloodstream to the uterus (4) causing contractions, pushing the fetus towards the cervix eventually inducing childbirth.
Image by Hannah.gray05
Brain Revealing Limbic System, Pituitary Gland and Hypothalamus
Brain Revealing Limbic System : 3D visualization of the lateral view of the brain. Through the transparent right hemisphere the inner structures of the brain can be seen collectively the limbic system.
Image by TheVisualMD
Pituitary Sinus
This image shows the pituitary gland situated in the pituitary sinus. It supports content explaining that the hormone oxytocin, produced in the hypothalamus and secreted by the pituitary, is released upon orgasm. Oxytocin can reduce pain and promote sleep.
Mark T McAuley1 , Rose Anne Kenny2 , Thomas BL Kirkwood1 , Darren J Wilkinson3 , Janette JL Jones4 and Veronica M Miller
Pituitary gland
Cancer Research UK uploader
Pituitary gland
Life Science Databases(LSDB)
Depressed Female with Visible Pituitary Gland
TheVisualMD
Pituitary Gland
TheVisualMD
Initimate Couple with visible Brain highlighting Pituitary
TheVisualMD
Thyroxine, Free (FT4): Pituitary Gland
TheVisualMD
Thyroxine, Total (T4): Pituitary Gland
TheVisualMD
Drawing of a body torso showing the brain, with the pituitary gland; the thyroid, with the 4 parathyroid glands; and the pancreas, with a detail of the pancreatic islets
NIDDK Image Library
Positive Feedback- Childbirth
Hannah.gray05
Brain Revealing Limbic System, Pituitary Gland and Hypothalamus
Image by Alan Hoofring (Illustrator) / National Cancer Institute
Pineal gland
Brain and Nearby Structures Description:The brain and nearby structures (including the skull, meninges, ventricles and spinal cord). An enlarged inset shows the skull, fluid, and brain.
Image by Alan Hoofring (Illustrator) / National Cancer Institute
Pituitary & Pineal Glands
Pituitary Gland
The pituitary gland or hypophysis is a small gland about 1 centimeter in diameter or the size of a pea. It is nearly surrounded by bone as it rests in the sella turcica, a depression in the sphenoid bone. The gland is connected to the hypothalamus of the brain by a slender stalk called the infundibulum.
There are two distinct regions in the gland: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The activity of the adenohypophysis is controlled by releasing hormones from the hypothalamus. The neurohypophysis is controlled by nerve stimulation.
Hormones of the Anterior Lobe (Adenohypophysis)
Growth hormone is a protein that stimulates the growth of bones, muscles, and other organs by promoting protein synthesis. This hormone drastically affects the appearance of an individual because it influences height. If there is too little growth hormone in a child, that person may become a pituitary dwarf of normal proportions but small stature. An excess of the hormone in a child results in an exaggerated bone growth, and the individual becomes exceptionally tall or a giant.
Thyroid-stimulating hormone, or thyrotropin, causes the glandular cells of the thyroid to secrete thyroid hormone. When there is a hypersecretion of thyroid-stimulating hormone, the thyroid gland enlarges and secretes too much thyroid hormone.
Adrenocorticotropic hormone reacts with receptor sites in the cortex of the adrenal gland to stimulate the secretion of cortical hormones, particularly cortisol.
Gonadotropic hormones react with receptor sites in the gonads, or ovaries and testes, to regulate the development, growth, and function of these organs.
Prolactin hormone promotes the development of glandular tissue in the female breast during pregnancy and stimulates milk production after the birth of the infant.
Hormones of the Posterior Lobe (Neurohypophysis)
Antidiuretic hormone promotes the reabsorption of water by the kidney tubules, with the result that less water is lost as urine. This mechanism conserves water for the body. Insufficient amounts of antidiuretic hormone cause excessive water loss in the urine.
Oxytocin causes contraction of the smooth muscle in the wall of the uterus. It also stimulates the ejection of milk from the lactating breast.
Pineal Gland
The pineal gland, also called pineal body or epiphysis cerebri, is a small cone-shaped structure that extends posteriorly from the third ventricle of the brain. The pineal gland consists of portions of neurons, neuroglial cells, and specialized secretory cells called pinealocytes. The pinealocytes synthesize the hormone melatonin and secrete it directly into the cerebrospinal fluid, which takes it into the blood. Melatonin affects reproductive development and daily physiologic cycles.
Source: National Cancer Institute (NCI)
Additional Materials (4)
Sleep and Why We Sleep
The pineal and pituitary glands secrete a number of hormones during sleep.
Image by CNX Openstax
Pineal gland
Diagram of pituitary and pineal glands in the human brain
Image by US Government cancer.gov
PINEAL AND PITUITARY GLAND
Diagram showing the pineal and pituitary glands
Image by Cancer Research UK uploader
The hypothalamus and pituitary gland | Endocrine system physiology | NCLEX-RN | Khan Academy
Video by khanacademymedicine/YouTube
Sleep and Why We Sleep
CNX Openstax
Pineal gland
US Government cancer.gov
PINEAL AND PITUITARY GLAND
Cancer Research UK uploader
6:35
The hypothalamus and pituitary gland | Endocrine system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
Posterior Pituitary
OXT and AVP synthesized in the neurons located in the PVN and SON
Image by Mauricio Aspé-Sánchez, Macarena Moreno, Maria Ignacia Rivera, Alejandra Rossi and John Ewer
OXT and AVP synthesized in the neurons located in the PVN and SON
Oxytocin (OXT) and arginine-vasopressin (AVP) are two closely related nonapeptides that exert their action on central and peripheral targets. (A) OXT and AVP are synthesized in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus. The peptidergic neurons in these nuclei project axons to the posterior pituitary, from where the peptides are released into the circulation. They act as hormones on peripheral targets, having well-documented actions (uterine contraction and vasoconstriction, for instance). In addition, dendrites of neurons in the PVN and the SON release the peptides directly into the brain, where they act as neurotransmitters or neuromodulators, regulating complex social cognition and behaviors. (B) OXT and AVP differ in only two aminoacids: this schematic drawing shows that, whereas the aminoacid sequence of OXT (top) includes an isoleucine at the third and a leucine at the eighth position, that of AVP (bottom) includes a phenylalanine and an arginine in the corresponding positions. Both peptides contain a cyclic six aminoacid ring, because of the disulfide bond formed by two cysteine residues.
Image by Mauricio Aspé-Sánchez, Macarena Moreno, Maria Ignacia Rivera, Alejandra Rossi and John Ewer
Posterior Pituitary
The posterior pituitary is actually an extension of the neurons of the paraventricular and supraoptic nuclei of the hypothalamus. The cell bodies of these regions rest in the hypothalamus, but their axons descend as the hypothalamic–hypophyseal tract within the infundibulum, and end in axon terminals that comprise the posterior pituitary (image).
Posterior Pituitary
Neurosecretory cells in the hypothalamus release oxytocin (OT) or ADH into the posterior lobe of the pituitary gland. These hormones are stored or released into the blood via the capillary plexus.
The posterior pituitary gland does not produce hormones, but rather stores and secretes hormones produced by the hypothalamus. The paraventricular nuclei produce the hormone oxytocin, whereas the supraoptic nuclei produce ADH. These hormones travel along the axons into storage sites in the axon terminals of the posterior pituitary. In response to signals from the same hypothalamic neurons, the hormones are released from the axon terminals into the bloodstream.
Oxytocin
When fetal development is complete, the peptide-derived hormone oxytocin (tocia- = “childbirth”) stimulates uterine contractions and dilation of the cervix. Throughout most of pregnancy, oxytocin hormone receptors are not expressed at high levels in the uterus. Toward the end of pregnancy, the synthesis of oxytocin receptors in the uterus increases, and the smooth muscle cells of the uterus become more sensitive to its effects. Oxytocin is continually released throughout childbirth through a positive feedback mechanism. As noted earlier, oxytocin prompts uterine contractions that push the fetal head toward the cervix. In response, cervical stretching stimulates additional oxytocin to be synthesized by the hypothalamus and released from the pituitary. This increases the intensity and effectiveness of uterine contractions and prompts additional dilation of the cervix. The feedback loop continues until birth.
Although the mother’s high blood levels of oxytocin begin to decrease immediately following birth, oxytocin continues to play a role in maternal and newborn health. First, oxytocin is necessary for the milk ejection reflex (commonly referred to as “let-down”) in breastfeeding women. As the newborn begins suckling, sensory receptors in the nipples transmit signals to the hypothalamus. In response, oxytocin is secreted and released into the bloodstream. Within seconds, cells in the mother’s milk ducts contract, ejecting milk into the infant’s mouth. Secondly, in both males and females, oxytocin is thought to contribute to parent–newborn bonding, known as attachment. Oxytocin is also thought to be involved in feelings of love and closeness, as well as in the sexual response.
Antidiuretic Hormone (ADH)
The solute concentration of the blood, or blood osmolarity, may change in response to the consumption of certain foods and fluids, as well as in response to disease, injury, medications, or other factors. Blood osmolarity is constantly monitored by osmoreceptors—specialized cells within the hypothalamus that are particularly sensitive to the concentration of sodium ions and other solutes.
In response to high blood osmolarity, which can occur during dehydration or following a very salty meal, the osmoreceptors signal the posterior pituitary to release antidiuretic hormone (ADH). The target cells of ADH are located in the tubular cells of the kidneys. Its effect is to increase epithelial permeability to water, allowing increased water reabsorption. The more water reabsorbed from the filtrate, the greater the amount of water that is returned to the blood and the less that is excreted in the urine. A greater concentration of water results in a reduced concentration of solutes. ADH is also known as vasopressin because, in very high concentrations, it causes constriction of blood vessels, which increases blood pressure by increasing peripheral resistance. The release of ADH is controlled by a negative feedback loop. As blood osmolarity decreases, the hypothalamic osmoreceptors sense the change and prompt a corresponding decrease in the secretion of ADH. As a result, less water is reabsorbed from the urine filtrate.
Interestingly, drugs can affect the secretion of ADH. For example, alcohol consumption inhibits the release of ADH, resulting in increased urine production that can eventually lead to dehydration and a hangover. A disease called diabetes insipidus is characterized by chronic underproduction of ADH that causes chronic dehydration. Because little ADH is produced and secreted, not enough water is reabsorbed by the kidneys. Although patients feel thirsty, and increase their fluid consumption, this doesn’t effectively decrease the solute concentration in their blood because ADH levels are not high enough to trigger water reabsorption in the kidneys. Electrolyte imbalances can occur in severe cases of diabetes insipidus.
Source: CNX OpenStax
Additional Materials (7)
Posterior Pituitary
Illustration of the Posterior Pituitary Complex
Image by Barbara Gomes de Oliveira
Pituitary Gland - Anterior and Posterior - Hormones
Neurosecretory cells in the hypothalamus release oxytocin (OT) or ADH into the posterior lobe of the pituitary gland. These hormones are stored or released into the blood via the capillary plexus.
Image by CNX Openstax
Major Pituitary Hormones
Major pituitary hormones and their target organs.
Image by CNX Openstax
Brain Revealing Pituitary Gland
Exercise works to ward off depression by secreting brain chemicals, endorphins, that are responsible for feelings of pleasure and well-being
Image by TheVisualMD
MRI of ectopic posterior pituitary
MRI of ectopic posterior pituitary
Image by Hellerhoff
Posterior Pituitary
Barbara Gomes de Oliveira
2:42
Pituitary Gland - Anterior and Posterior - Hormones
The anterior pituitary originates from the digestive tract in the embryo and migrates toward the brain during fetal development. There are three regions: the pars distalis is the most anterior, the pars intermedia is adjacent to the posterior pituitary, and the pars tuberalis is a slender “tube” that wraps the infundibulum.
Recall that the posterior pituitary does not synthesize hormones, but merely stores them. In contrast, the anterior pituitary does manufacture hormones. However, the secretion of hormones from the anterior pituitary is regulated by two classes of hormones. These hormones—secreted by the hypothalamus—are the releasing hormones that stimulate the secretion of hormones from the anterior pituitary and the inhibiting hormones that inhibit secretion.
Hypothalamic hormones are secreted by neurons, but enter the anterior pituitary through blood vessels (image). Within the infundibulum is a bridge of capillaries that connects the hypothalamus to the anterior pituitary. This network, called the hypophyseal portal system, allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation. The system originates from the superior hypophyseal artery, which branches off the carotid arteries and transports blood to the hypothalamus. The branches of the superior hypophyseal artery form the hypophyseal portal system (see image). Hypothalamic releasing and inhibiting hormones travel through a primary capillary plexus to the portal veins, which carry them into the anterior pituitary. Hormones produced by the anterior pituitary (in response to releasing hormones) enter a secondary capillary plexus, and from there drain into the circulation.
Anterior Pituitary
The anterior pituitary manufactures seven hormones. The hypothalamus produces separate hormones that stimulate or inhibit hormone production in the anterior pituitary. Hormones from the hypothalamus reach the anterior pituitary via the hypophyseal portal system.
The anterior pituitary produces seven hormones. These are the growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), beta endorphin, and prolactin. Of the hormones of the anterior pituitary, TSH, ACTH, FSH, and LH are collectively referred to as tropic hormones (trope- = “turning”) because they turn on or off the function of other endocrine glands.
Growth Hormone
The endocrine system regulates the growth of the human body, protein synthesis, and cellular replication. A major hormone involved in this process is growth hormone (GH), also called somatotropin—a protein hormone produced and secreted by the anterior pituitary gland. Its primary function is anabolic; it promotes protein synthesis and tissue building through direct and indirect mechanisms (image). GH levels are controlled by the release of GHRH and GHIH (also known as somatostatin) from the hypothalamus.
Hormonal Regulation of Growth
Growth hormone (GH) directly accelerates the rate of protein synthesis in skeletal muscle and bones. Insulin-like growth factor 1 (IGF-1) is activated by growth hormone and indirectly supports the formation of new proteins in muscle cells and bone.
A glucose-sparing effect occurs when GH stimulates lipolysis, or the breakdown of adipose tissue, releasing fatty acids into the blood. As a result, many tissues switch from glucose to fatty acids as their main energy source, which means that less glucose is taken up from the bloodstream.
GH also initiates the diabetogenic effect in which GH stimulates the liver to break down glycogen to glucose, which is then deposited into the blood. The name “diabetogenic” is derived from the similarity in elevated blood glucose levels observed between individuals with untreated diabetes mellitus and individuals experiencing GH excess. Blood glucose levels rise as the result of a combination of glucose-sparing and diabetogenic effects.
GH indirectly mediates growth and protein synthesis by triggering the liver and other tissues to produce a group of proteins called insulin-like growth factors (IGFs). These proteins enhance cellular proliferation and inhibit apoptosis, or programmed cell death. IGFs stimulate cells to increase their uptake of amino acids from the blood for protein synthesis. Skeletal muscle and cartilage cells are particularly sensitive to stimulation from IGFs.
Dysfunction of the endocrine system’s control of growth can result in several disorders. For example, gigantism is a disorder in children that is caused by the secretion of abnormally large amounts of GH, resulting in excessive growth. A similar condition in adults is acromegaly, a disorder that results in the growth of bones in the face, hands, and feet in response to excessive levels of GH in individuals who have stopped growing. Abnormally low levels of GH in children can cause growth impairment—a disorder called pituitary dwarfism (also known as growth hormone deficiency).
Thyroid-Stimulating Hormone
The activity of the thyroid gland is regulated by thyroid-stimulating hormone (TSH), also called thyrotropin. TSH is released from the anterior pituitary in response to thyrotropin-releasing hormone (TRH) from the hypothalamus. As discussed shortly, it triggers the secretion of thyroid hormones by the thyroid gland. In a classic negative feedback loop, elevated levels of thyroid hormones in the bloodstream then trigger a drop in production of TRH and subsequently TSH.
Adrenocorticotropic Hormone
The adrenocorticotropic hormone (ACTH), also called corticotropin, stimulates the adrenal cortex (the more superficial “bark” of the adrenal glands) to secrete corticosteroid hormones such as cortisol. ACTH come from a precursor molecule known as pro-opiomelanotropin (POMC) which produces several biologically active molecules when cleaved, including ACTH, melanocyte-stimulating hormone, and the brain opioid peptides known as endorphins.
The release of ACTH is regulated by the corticotropin-releasing hormone (CRH) from the hypothalamus in response to normal physiologic rhythms. A variety of stressors can also influence its release, and the role of ACTH in the stress response is discussed later in this chapter.
Follicle-Stimulating Hormone and Luteinizing Hormone
The endocrine glands secrete a variety of hormones that control the development and regulation of the reproductive system (these glands include the anterior pituitary, the adrenal cortex, and the gonads—the testes in males and the ovaries in females). Much of the development of the reproductive system occurs during puberty and is marked by the development of sex-specific characteristics in both male and female adolescents. Puberty is initiated by gonadotropin-releasing hormone (GnRH), a hormone produced and secreted by the hypothalamus. GnRH stimulates the anterior pituitary to secrete gonadotropins—hormones that regulate the function of the gonads. The levels of GnRH are regulated through a negative feedback loop; high levels of reproductive hormones inhibit the release of GnRH. Throughout life, gonadotropins regulate reproductive function and, in the case of women, the onset and cessation of reproductive capacity.
The gonadotropins include two glycoprotein hormones: follicle-stimulating hormone (FSH) stimulates the production and maturation of sex cells, or gametes, including ova in women and sperm in men. FSH also promotes follicular growth; these follicles then release estrogens in the female ovaries. Luteinizing hormone (LH) triggers ovulation in women, as well as the production of estrogens and progesterone by the ovaries. LH stimulates production of testosterone by the male testes.
Prolactin
As its name implies, prolactin (PRL) promotes lactation (milk production) in women. During pregnancy, it contributes to development of the mammary glands, and after birth, it stimulates the mammary glands to produce breast milk. However, the effects of prolactin depend heavily upon the permissive effects of estrogens, progesterone, and other hormones. And as noted earlier, the let-down of milk occurs in response to stimulation from oxytocin.
In a non-pregnant woman, prolactin secretion is inhibited by prolactin-inhibiting hormone (PIH), which is actually the neurotransmitter dopamine, and is released from neurons in the hypothalamus. Only during pregnancy do prolactin levels rise in response to prolactin-releasing hormone (PRH) from the hypothalamus.
Source: CNX OpenStax
Additional Materials (5)
Medial Forebrain Bundle
Diagram illustrating the anatomical location of medial forebrain bundle. These neural fibres connect the septal area in forebrain with medial hypothalamus.
Image by Yukaizou2016
Brain Revealing Limbic System, Pituitary Gland and Hypothalamus
Brain Revealing Limbic System : 3D visualization of the lateral view of the brain. Through the transparent right hemisphere the inner structures of the brain can be seen collectively the limbic system.
Image by TheVisualMD
Pituitary gland
Diagram of pituitary and pineal glands in the human brain
Image by Images are generated by Life Science Databases(LSDB)
Hypothalamus Control of the Anterior Pituitary Gland - Hypothalmic Control
Video by 5MinuteSchool/YouTube
What is the Pituitary Gland?
Video by Swedish/YouTube
Medial Forebrain Bundle
Yukaizou2016
Brain Revealing Limbic System, Pituitary Gland and Hypothalamus
TheVisualMD
Pituitary gland
Images are generated by Life Science Databases(LSDB)
1:56
Hypothalamus Control of the Anterior Pituitary Gland - Hypothalmic Control
The cells in the zone between the pituitary lobes secrete a hormone known as melanocyte-stimulating hormone (MSH) that is formed by cleavage of the pro-opiomelanocortin (POMC) precursor protein. Local production of MSH in the skin is responsible for melanin production in response to UV light exposure. The role of MSH made by the pituitary is more complicated. For instance, people with lighter skin generally have the same amount of MSH as people with darker skin. Nevertheless, this hormone is capable of darkening of the skin by inducing melanin production in the skin’s melanocytes. Women also show increased MSH production during pregnancy; in combination with estrogens, it can lead to darker skin pigmentation, especially the skin of the areolas and labia minora. image is a summary of the pituitary hormones and their principal effects.