Endocrine System flashcards

Hypothalamus
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Hypothalamus
This gland is a part of the brain that consists of neurosecretory cells. They connect both the nervous and the endocrine system. The hypothalamus secretes various releasing hormones like gonadotropin-releasing hormones and growth hormone-releasing hormones. These hormones act on the pituitary gland to stimulate other glands.
Hormones Secreted by Hypothalamus
The anterior region of the hypothalamus is responsible for hormone secretion. The nuclei present in this region lead the process. The important hormones secreted by hypothalamus are:

Corticotropin-Releasing Hormone: This hormone is responsible for the regulation of metabolic and immune response.

Thyrotropin Releasing Hormone: It triggers the pituitary gland to release a thyroid-stimulating hormone which plays a major role in the functioning of organs of the body such as heart, muscles, etc.

Gonadotropin-Releasing Hormone: It stimulates the pituitary gland to release several reproductive hormones.

Oxytocin: It is involved in several processes such as lactation, childbirth, regulating sleep cycles, maintaining body temperature.

Somatostatin: This hormone is also known as Growth Hormone Inhibiting Hormone. It regulates the endocrine system and affects the neurotransmission and cell proliferation by interacting with G-protein coupled receptors.
Pituitary Gland
The master gland. It is a pea-sized gland that is located at the bottom of the brain. It controls and regulates other glands in the body. Hormones released by this gland are growth hormone, thyroid-stimulating hormone, LH, FSH etc.
Anterior Pituitary Hormones
The anterior pituitary is responsible for the synthesis and secretion of several key hormones in the body. These hormones include:
Human Growth Hormone (HGH): Responsible for the growth and repair of all cells in the body.

Thyroid Stimulating Hormone (TSH): Influences the thyroid gland for the release of thyroxine, its own hormone. TSH is also called Thyrotropin.

Adrenocorticotropic Hormone (ACTH): Influences the adrenal gland to release of Cortisol or the "stress hormone". ACTH is also known as corticotropin.

Luteinising Hormone (LH) and Follicle-Stimulating Hormone (FSH): Collectively known as Gonadotropins, LH and FSH control the sexual and reproductive characteristics in males and females.
Prolactin (PRL): Produces milk in the breast. Though it is present at all times, the secretion is increased during and just after pregnancy.

Melanocyte-Stimulating Hormone (MSH): Involved in the stimulation of the production of melanin by skin and hair.
Pineal Gland
This gland is also located in the brain. It releases the hormone called melatonin which regulates the wake-up and sleep clock and helps in immunity etc.
Hormones Secreted by Pineal Gland- Melatonin
The pineal gland synthesises melatonin and serotonin, hence they are also called as the Pineal Gland Hormone. The pineal gland also produces neurosteroids.
Serotonin is the precursor of melatonin. Serotonin is acetylated and methylated to yield melatonin within the pineal gland. The light exposure to the eyes affects the synthesis and secretion of melatonin.
Two melatonin receptors have been found in mammals- Mel1A and Mel1B. These are G-protein coupled cell surface receptors.
Melatonin affects circadian rhythm.
Our circadian rhythm is a 24-hour biological cycle, characterised by the sleep-wake patterns. The daylight and darkness regulate our circadian rhythms. The secretion of melatonin is stopped on exposure to light which in turn controls the circadian rhythm. The secretion of melatonin is high during dark and low during daylight. This influences our reaction to photoperiod.
The secretion of gonadotropins from the anterior Pituitary gland is blocked by melatonin thereby affecting reproduction. These hormones aid in the development of ovaries and testes.
Thyroid gland
This is a butterfly-shaped paired gland located in the neck region. It releases the hormones triiodothyronine (T3) and thyroxine (T4). These hormones regulate body metabolism. Iodine is vital for thyroxine synthesis. Its deficiency leads to a disease called goitre.
Thyroid Hormones
There are two thyroid hormones:
T4: Thyroxine (Tetraiodothyronine)
T3: Triiodothyronine
T4
Thyroxine is a hormone secreted by the thyroid gland in the bloodstream. It then travels to the organs such as kidneys and liver where it gets converted into and gets converted into its active form triiodothyronine.
T3
It is a thyroid hormone that affects physiological processes such as growth, development, metabolism, etc.
Parathyroid Gland
This gland is located near the Thyroid gland in the neck region. The hormone released by this gland is called Parathyroid hormone, which regulates calcium and phosphorus level in bones.
There are two main types of Parathyroid hormone:
Parathormone
Calcitonin
The primary purpose of parathyroid glands is to regulate calcium in the blood in a very strict range between 9.0 and 10.1 mg/dL. Parathyroids also manage the amount of calcium in the bones and determine their strength.
Bones - The parathyroid hormone (PTH) stimulates the release of calcium from stores of calcium present in the bones into the bloodstream.
Intestine - PTH increases the calcium absorption in the intestine by food through its impacts and affects the metabolism of vitamin D.
Kidneys - PTH minimizes the calcium loss in the urine and also stimulates active vitamin D formation in the kidneys.
Pancreasan endocrine as well as an exocrine gland. That is why the Pancreas is also known as a mixed gland. The pancreas secretes hormones like glucagon and insulin; these two hormones balance the blood sugar level in the body. Other hormones secreted are somatostatin and pancreatic polypeptide.What is the pancreas?an abdominal organ located behind the stomach and surrounded by spleen, liver and small intestine. It is a vital part of the digestive system and is responsible for regulating blood sugar levels. The pancreas secretes digestive enzymes such as amylase, proteases and lipase into the duodenum. These enzymes help in digesting sugar, proteins and fat respectively. Islets of Langerhans are embedded in the pancreas that secretes hormones such as insulin and glucagon into the blood.Pancreas FunctionThe pancreas performs the following functions: Exocrine Function The pancreas consists of exocrine glands that produce enzymes trypsin and chymotrypsin that are essential for digestion. These enzymes contain chymotrypsin and trypsin to digest proteins, amylase for the digestion of carbohydrates and lipase to break down fats. These pancreatic juices are liberated into the system of ducts and culminated in the pancreatic duct when the food enters the stomach. Endocrine Function The endocrine part of the pancreas comprises Islets of Langerhans that release insulin and glucagon directly into the bloodstream. They help in regulating the blood sugar levels of the body.Adrenal Glandshave two regions known as the adrenal cortex and adrenal medulla. The cortex region of the adrenal gland secretes the hormones cortisol, aldosterone, and androgens while the medulla region secretes the hormones adrenaline and noradrenaline. Adrenaline is the hormone responsible for the fight or flight response of the body in times of emergency.Adrenal Gland HormonesEpinephrine: Also called adrenaline, this hormone rapidly responds to stress by increasing the heart rate and raising blood glucose levels in the blood. Norepinephrine: Also called noradrenaline, this hormone works with epinephrine in reacting to stress. Its primary function is to mobilize the body and brain for action. Hydrocortisone: It is commonly known as cortisol or a steroid hormone. It is involved in regulating body functions like the conversion of fats, and carbohydrates to energy and also plays a vital role in other metabolic processes. Corticosterone: This hormone works with hydrocortisone to control the immune response and prevents inflammatory reactions.Adrenal Gland DisordersAdrenal Gland disorders appear when not enough hormones or inadequate hormones are produced by the adrenal glands. Even abnormal growths or tumours can cause certain illness. Cushing's Syndrome is a condition where the cortisol levels in the body are very high. The cause can be a tumour in the adrenal gland or the pituitary gland. Adrenocortical carcinoma is a cancerous tumour that usually develops in the outer layer of the adrenal gland. This type of tumour is typically found years after they have spread to other organs in the body. Congenital Adrenal Hyperplasia (CAH) is a genetic disorder characterized by very low levels of cortisol production. The people inflicted with this condition may also have other hormonal imbalances where their bodies may make very little aldosterone, but too much androgen. Addison's Disease is caused when adrenal glands produce insufficient cortisol or aldosterone. It results in weakness, fatigue, low blood pressure, nausea, etc. In 70% of cases, Addisone disease is caused due to autoimmune disorder, where the body mistakenly attacks the adrenal glands. As a result, the adrenal gland does not produce the hormone aldosterone in sufficient quantities.Adrenal Gland FunctionOne of the most well-known responses - the Fight or Flight Response is triggered by the release of stress hormones from the adrenal glands. The adrenal glands produce a variety of hormones. These hormones are very crucial for the normal functioning of the body. For instance, the glands secrete cortisol, which has anti-inflammatory properties and aids the immune system. The adrenal gland also helps to regulate metabolism and blood pressure through various other hormones.Gonadsreproductive glands present in males and females. The male gonad is the pair of testes which secretes the hormone testosterone. This is responsible for the secondary sexual characteristics in males. The female gonad consists of a pair of ovaries. They secrete two hormones estrogen and progesterone. Both of these regulate secondary sexual characteristics in females.Male Gonad HormonesAndrogens are hormones that majorly influence the development of the male reproductive system. Testosterone is responsible and essential for increased growth of bone and muscle, growth of body hair, developing broader shoulder, voice deepening and growth of the penis. Androstenedione - These are the hormones that act as a precursor to estrogens and testosterone. Inhibin - These hormones inhibit the release of FSH and thought to be involved in sperm cell regulation and development.Female Gonad HormonesThe major hormones of the ovaries are progesterone and estrogens. Estrogens - It is a group of female sex hormones essential for reproduction and the development of the female reproductive system. Estrogens are responsible for maturation and growth of the vagina and uterus, widening of pelvis, breast and the uterus changes during the menstrual cycle, and increasing growth of hairs on the body. Progesterone - These are the hormones whose function is to prepare the uterus for conception, regulating changes in the uterus during the Menstrual cycle, ovulation aids, and stimulating gland development for the production of milk during pregnancy.OvariesThey secrete two hormones estrogen and progesterone. Both of these regulate secondary sexual characteristics in females.HypothalamusA part of the lower middle brain that tells the pituitary gland when to release hormones.OvariesThe female reproductive organs that release eggs and produce sex hormones.Islet cells in the pancreasCells in the pancreas control the release of the hormones insulin and glucagon.ParathyroidFour tiny glands in the neck that play a role in bone development.Pineal glandA gland found near the center of the brain that may be linked to sleep patterns.Pituitary glandA gland found at the base of brain behind the sinuses. It is often called the "master gland" because it influences many other glands, especially the thyroid. Problems with the pituitary gland can affect bone growth, a woman's menstrual cycles, and the release of breast milk.TestesThe male reproductive glands that produce sperm and sex hormones.ThymusA gland in the upper chest that helps develop the body's immune system early in life.ThyroidA butterfly-shaped gland in the front of the neck that controls metabolism.Endocrine disorders are typically grouped into two categories:Endocrine disease that results when a gland produces too much or too little of an endocrine hormone, called a hormone imbalance. Endocrine disease due to the development of lesions (such as nodules or tumors) in the endocrine system, which may or may not affect hormone levels.Adrenal insufficiencyThe adrenal gland releases too little of the hormone cortisol and sometimes, aldosterone. Symptoms include fatigue, stomach upset, dehydration, and skin changes. Addison's disease is a type of adrenal insufficiency.Cushing's diseaseOverproduction of a pituitary gland hormone leads to an overactive adrenal gland. A similar condition called Cushing's syndrome may occur in people, particularly children, who take high doses of corticosteroid medications.Gigantism (acromegaly) and other growth hormone problemsIf the pituitary gland produces too much growth hormone, a child's bones and body parts may grow abnormally fast. If growth hormone levels are too low, a child can stop growing in height.HyperthyroidismThe thyroid gland produces too much thyroid hormone, leading to weight loss, fast heart rate, sweating, and nervousness. The most common cause for an overactive thyroid is an autoimmune disorder called Grave's disease.HypothyroidismThe thyroid gland does not produce enough thyroid hormone, leading to fatigue, constipation, dry skin, and depression. The underactive gland can cause slowed development in children. Some types of hypothyroidism are present at birth.HypopituitarismThe pituitary gland releases little or no hormones. It may be caused by a number of different diseases. Women with this condition may stop getting their periods.Polycystic ovary syndrome (PCOS)Overproduction of androgens interfere with the development of eggs and their release from the female ovaries. PCOS is a leading cause of infertility.Addison's diseasehappens when there is not enough of cortisol or aldosterone. These hormones are produced by the adrenal glands.Symptoms of Addison's diseaseLoss of weight and appetite Blood pressure that is low Fainting Craving salt Extreme tiredness Hyperpigmentation (skin becomes dark) Hypoglycemia (low blood sugar) Pain in the abdomen Vomiting, nausea, and diarrhea Pain in the joints and muscles Depression Sexual dysfunction in and loss of body hair IrritabilityCushing's DiseaseThis condition is what happens when a pituitary gland produces too many hormones. The end result is an adrenal gland that is overactive.Cushing disease/syndromeSymptoms - While the symptoms vary, changes in skin and increasing obesity are two of the common signs of this disease. Others include: Skin that has become thin, fragile and bruises right away Stretch marks on the breasts, arms, abdomen and thighs Deposits of fatty tissue along with weight gain in a number of places, including the face, upper back, between the shoulders, and around the middle of the body Cuts, infections and insect bites that heal slowly Breakouts on the skinHypothalamusServes as a central endocrine control centre by communication with the pituitary gland and has many different functions such as growth, thermoregulation, control of hunger and thirst, sexual development and regulation of stress defenses Hypothalamic disease, which in turn can cause the disorders belowPituitary glandControlled by the releasing and inhibiting hormones from the hypothalamus, many endocrine functions are regulated by this gland. The hormones either released or inhibited are: anti‐diuretic hormone (ADH) and oxytocin from the posterior pituitary gland (PG) and growth hormone (somatotropin), thyroid‐stimulating hormone (TSH), adreno‐cortico trophic hormone (ACTH) follicle‐stimulating hormone, luteinising hormone, prolactin, melanocyte‐stimulating hormone, beta‐endorphin from the anterior PG Hypopituitarism Pituitary dwarfism/poor somatic growth Gigantism Diabetes insipidus Pituitary tumours, such as:craniopharyngiomaprolactinomapituitary adenomaPineal glandPineal disease/dysfunction, e.g., disruption to the sleep-wake cycle (circadian rhythms)Thyroid glandReleases thyroxine that regulates metabolism, stimulates body oxygen and energy consumption, plays a part in growth by promoting protein synthesis and influences the activity of the nervous system. Calcitonin lowers calcium levels of calcium Hypothyroidism Hyperthyroidism ('Graves')Parathyroid glandReleases parathyroid hormone that raises blood calcium level and decreases phosphate level by increasing the rate of calcium absorption from the intestine into the blood Hypoparathyroidism HyperparathyroidismThymus glandReleases thymosin and other related hormones that play an integral role in the maturation of T cells as part of the immune system Thymus disease/dysfunction, e.g., interference with normal immune responseAdrenal glandProduces mineralocorticoids that stimulate sodium reabsorption in the kidneys increasing blood levels of sodium and water, corticosteroids that stimulate gluconeogenesis and fat breakdown in adipose tissue so increasing glucose availability in the blood, promote metabolism and resistance to stress and gonadocorticoids, which influence masculinisation (virilisation) in both males and females. Adrenaline and noradrenaline from the adrenal medulla are an integral part of the body's flight-fight responses to stress Adrenal insufficiency: Addison's disease. Cushing disease Congenital adrenal hyperplasiaPancreasProduces and releases insulin which results in targets cells taking up free glucose so lowering blood levels. Conversely, glucagon is also released that targets the liver to break down glycogen into glucose which increases blood glucose levels Diabetes mellitus Hyperinsulinemia/nesidioblastosisTestes and ovariesRelease sex hormones testosterone or oestrogen from either the testes or ovaries Disorders of sex development (DSD) or ambiguous genitalia Gonadotropin deficiency - failure to initiate or complete puberty Precocious puberty Ovarian disease