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Endocrinology - Coggle Diagram

- - - - They act by regulating preexisting reaction
  - - - receptors are found in cytoplasm or in nucleus
      - hormone must first be released from the carrier protein before entering the cell
        
        the hormone receptor complex then binds to DNA in the nucleus to alter cell activity (increase or decrease protein production)
    - - receptors found on surface
      - when the hormone attaches to the receptor, a sequence of chemical reactions is triggered, altering cell activity
      - how the receptor affects the cell after hormone binding
        
        second messenger system
        
        triggers G-protein on inside to produce a second messenger (most commonly studied is cAMP)
        
        cAMP is already released in the cytoplasm, altering preexisting proteins in the cell
        
        the proteins alter a sequence of reactions in the cell, leading to many intracellular response (including release of proteins)
        
        G-protein
        
        tyrosine kinase
        
        the receptor activates tyrosine kinase on the inside surface of the membrane
        
        tyrosine kinase activates existing proteins, which alter cell activity (tyrosine kinase acts like the second messenger)
        
        G-proteins
        
        when the hormone attaches to the receptor, the G-protein in the membrane is activated
        
        the G-protein can open adjacent ion channels
        
        if the ion is Ca++, it acts as a second messenger, altering preexisting proteins in the cell
- - - - thyroxine
      - triiodothyronine
      - properties
        
        hydrophobic property means they need a protein carrier
        
        hydrophobic property allows them to diffuse across the cell membrane
        
        its receptor is found inside the cell as it can diffuse inside
    - - calcitonin
      - parathyroid hormone
      - the pituitary and pancreatic hormones
      - most of releasing and inhibiting hormones originating from hypothalamus
      - properties
        
        hydrophilic, so requires a can freely diffuse in blood
        
        hydrophilic so needs transporting channels to get across the membrane
        
        their receptors are found outside the target cell
      - insulin
    - - cortisol
      - aldosterone
      - estrogen
      - progesterone
      - testoterone
      - properties
        
        hydrophobic, so requires a protein carrier to help them circulate in the blood
        
        hydrophobic property allows them to diffuse easily across the cell membrane
        
        their receptors are found inside the target cell
- - - - to perform these functions, the hypothalamus receives all kinds of info such as metabolism, hormonal, temperature and neural info
    - - this is saying one hormone from hypothalamus can affect the hormone release activity of the pituitary
      - prolactin releasing hormone (PRH)
      - prolactin inhibiting hormone (PIH)
        
        aka dopamine
      - Thyrotropin Releasing Hormone (TRH)
      - Corticotropin Releasing Hormone (CRH)
      - Growth Hormone releasing Hormone(GHRH)
      - Growth Hormone inhibiting Hormone(GHIH)
      - Gonadotropin Releasing Hormone (GnRH)
  - - - divided into
        
        anterior pituitary
        
        forms from tissues that forms the roof of the mouth
        which is made of endocrine tissues
        
        the cells here secrete pituitary hormones into the blood
        
        this part of the pituitary is regulated by the hypothalamus through the hypothalamic-hypophyseal portal system
        
        hypothalamic-hypophyseal portal system
        
        the hypothalamus communicates with the anterior pituitary by secreting inhib or release hormones into this portal system
        
        the secretion of hormone into this portal causes the control of anterior pituitary activity
        
        function relies on blood flow
        
        posterior pituitary
        
        forms from the neural tissues at the base of the brain
        
        has axons and nerve terminals in which the cell body is found in the hypothalamus
        
        the tract of neurons is called the hypothalamic-hypophyseal tract
        
        hypothalamic-hypophyseal tract
        
        the neurons here produce neurohormones such as ADH and oxytocin that are secreted into the blood from the posterior pituitary
        
        this secretion of hormones is caused as a response to action potentials
    - - anterior pituitary
        
        controls metabolic functions in the body
        
        some anterior hormones control growth of the ovaries and testes as well as their reproductive functions
        
        hormones of the anterior pituitary
        
        when the hypothalamus releases thyroid releasing hormone (TRH)
        
        the anterior pituitary releases thyroid stimulating hormone (TSH)
        
        TSH causes the thyroid gland to release 2 thyroid hormones (T3 and T4)
        
        when hypothalamus releases corticotropin releasing hormone (CRH)
        
        CRH causes releases of adrenocorticotropic hormone (ACTH) from the anterior pituitary
        
        ACTH mostly stimulates the release of cortisol in the adrenal glands
        
        ACTH also has little effect on secretion of androgens and aldosterone
        
        when PRH is released in hypothalamus
        
        prolactin is released in the anterior pituitary
        
        breasts produce milk
        
        hypothalamus releases GHRH
        
        growth hormone is released in the anterior pituitary
        
        many tissues are affected
        
        releasing of gonadotropin releasing hormone (GnRH) in hypothalamus
        
        release of luteinizing hormone (LH) or follicle stimulating hormone (FSH) in anterior pituitary
        
        activates male and female gonads
      - posterior pituitary
        
        2 hormones are released here
        
        ADH/vassopressin
        
        oxytocin
      - regulation by negative feedback
        
        The second hormone, third hormone or the target tissue response from the third hormone can cause a feedback loop to inhibit hormone release in the hypothalamus
        
        if it's the second hormone, creates short loop
        
        if it's third hormone, creates long loop
        
        if it's the target cell tissues, it's a ultra long loop
        
        hormone products can feedback to inhibit it's own production
  - - - the follicles are composed of a central region made of colloid and are surrounded by epithelial cells
      - between follicles, there are parafollicular cells (aka C cells)
    - - first organ in the body to be identified as a gland
      - produces the hormones triiodothyronine (T3) and thyroxine (T4) which contain iodine
        
        T3 and T4 regulate the basal metabolic rate of the body
        
        T3 and T4 are made from tyrosine (hydrophobic side chain)
        
        this property means they need a protein carrier to circulate in the blood, but can diffuse through the cell membrane on their own
        
        T3 and T4 are made by combining iodine and tyrosine using the glycoprotein thyroglobulin
        
        this is done in the epithelial cells where they take up molecules of tyrosine from circulation and combine it to thyroglobin made in these cells
        
        the epithelial cells also take up iodine which comes from the diet
        
        when the tyrosine-thyroglobulin complex is secreted into the colloid, ONE or TWO molecules of iodine attach to the tyrosine
        
        1 more item...
        
        T3 and T4 are made in the epithelial cells
    - - calcitonin decreases calcium levels in the blood
        
        performs this function by decreasing the number and activity of osteoclasts
        
        osteoclasts are bone-dissolving cells that breakdown bone into calcium and releases it into the blood
      - calcitonin
        
        specifically secreted by the parafollicular cells (aka C cells) of the thyroid
        
        the C cells make up 0.1% of the human thyroid
        
        regulates calcium levels in blood and is secreted when calcium levels are ABOVE normal
        
        stimulates (increases) calcium secretion in the urine to decreases blood calcium levels
        
        this protein hormone works with parathyroid hormone (PTH) to perform its function
    - - when TSH is released from the pituitary gland, it will bind to the receptor on the membrane of the epithelial cell, stimulating many reactions
        
        these rxns include
        
        trapping and circulating iodine T3 and T4
        
        stimulates endocytosis of T3 and T4 thyroglobulin
        
        enzymatic removal of thyroglobulin from T3 and T4 epithelial cells
        
        secretion of T3 and T4 into the blood
        
        TSH can also stimulate the thyroid to grow in a process called hyperplasia
      - when T3 and T4 are secreted into the blood, they will feedback into the hypothalamus and pituitary
        
        this stops the release of thyrotropin release hormone and TSH
        
        less TSH circulating to the thyroid means less release of T3 and T4 into the blood
    - - 90% of hormones released from the thyroid gland is T4
        
        both require blood proteins to be circulated in the blood
        
        most of T4 released is converted to T3 which is more biologically active than T4
      - 10% of hormones released from the thyroid gland is T3
    - - their hydrophobic nature allows them to diffuse through the cell membrane
      - T3 and T4 receptors are found on the nucleus of cells which when bound can alter transcription of proteins
        
        the proteins transcribed are used as enzymes to enhance the metabolic activity of the cell
        
        specifically, T3 and T4 regulates the body's basal metabolic rate (BMR) which is the amount of energy and O2 used by the body at rest
        
        least amount of energy a person will use
      - T3 and T4 is also important for proper development of the nervous system in the fetus
      - it also helps maintain a person's alertness, responsiveness and emotional state
      - increase of T3 and T4 will cause
        
        increase body temp
        
        increase cardiac output
        
        increase ventilation
        
        increase food intake
        
        increase breakdown of carbohydrates, fat and protein
    - - too much of this hormone can lead to diseases in infants and adults (however not essential for life)
        
        infants
        
        insufficient of thyroid hormones (hypothyroidism)
        
        causes cretinism
        
        characterized by
        
        dwarfism
        
        mental retardation
        
        can be prevented by thyroid hormone treatments
        
        caused by
        
        congenital lack of thyroid gland (lack of this hormone at birth)
        
        body cannot produce T3 or T4 due to genetic defect or lack of iodine in the diet
        
        adults
        
        hypothyroidism (lack of thyroid hormones)
        
        low basal metabolic rate
        
        sensitive to cold temps
        
        weight gain due to slow fat breakdown and increased fat storage
        
        low blood pressure
        
        slow reflexes, apathy and lethargy (low energy and lack of interest)
        
        depression
        
        easily fatigued
        
        hyperthyroidism (excess of thyroid hormone)
        
        high basal metabolic rate
        
        sensitive to warm temperatures
        
        rapid HR
        
        weight loss from increased fat breakdown and decreased fat storage
        
        hyperactive/"nervous" activity
        
        goiter
        
        caused by enlargement of the thyroid gland
        
        this comes from many factors
        
        insufficient iodine
        
        this causes the thyroid to be unable to produce T3/T4
        
        1 more item...
        
        too much thyrotropin releasing hormone (TRH)
        
        can be caused by overexcretion from a hypothalamic tumor
        
        too much thyroid stimulating hormone (TSH)
        
        this causes the thyroid to grow uncontrollably
    - - found on the posterior (back) side of the thyroid and is 6 mm long, 3 mm wide and 2 mm thick
      - secretes parathyroid hormone (PTH) when blood calcium levels are LOW
        
        reacts antagonistically (oppositely) to calcitonin by increasing calcium levels
        
        with no PTH, the kidney would continuously excreted calcium, depleting extracellular fluid and bones
      - performs its function by
        
        increasing number and activity of bone-dissolving osteoclasts cells to release calcium in blood
        
        decrease excretion of calcium in the urine by promoting calcium reabsorption
- - - - there are two present in the body and they sit on top of each kidney
      - made up of neural tissue and glandular tissue
      - the inner medulla layer is made up of neural tissue
        
        this layer is controlled by the sympathetic nervous system
        
        the medulla of the adrenal gland secretes epinephrine (adrenaline)
      - the outer cortex layer is endocrine and is controlled by pituitary hormones
      - 3 layers
        
        zona glomerulosa
        
        secretes aldosterone
        
        aldosterone is a mineralcorticoid that regulates mineral and fluid volume of the kidney
        
        zona fasciculata
        
        secretes the glucocorticoid hormone, cortisol
        
        zona reticularis
        
        secretes small amount of androgens (sex steroid hormones)
        
        they all look different because they all contain different cell types that secrete different hormones
        
        the hormones secreted are all steroid hormones (hydrophobic)
    - - SYN stimulates the adrenal gland
        
        causes epinephrine secretion from the adrenal medulla into the blood
        
        epinephrine increases HR, force of contraction and blood flow to heart and skeletal muscle
        
        happens during fight/flight situation
      - aldosterone is secreted in the adrenal gland in response to angiotensin II, low Na+/ high K+ in blood or in response to adrenocorticotropic hormone (ACTH)
        
        Aldosterone stimulates Na+ reabsorption in the nephron
        
        androgens is also released from the zona reticularis in response to ACTH
      - cortisol
        
        is usually constantly secreted by the adrenal gland
        
        secretion and production increases with physical(hot/cold), physiological (pain), emotional or social stress
        
        stress stimulates the hypothalamus to release corticotropin releasing hormone (CRH)
        
        CRH causes the anterior pituitary to secrete adrenocorticotropic hormone (ACTH)
        
        ACTH stimulates the adrenal gland to produce cortisol, aldosterone and androgens
        
        the cortisol made can negatively feedback to the hypothalamus and anterior pituitary to decrease release of CRH and ACTH
        
        steroid hormone so must be carried by proteins in blood (hydrophobic)
        
        the hormone must diffuse through the cell membrane and attach to receptors in the cytoplasm
        
        the cortisol-receptor complex moves to the nucleus of the cell to have it's effect on the cell
        
        varying levels of cortisol throughout the day
        
        varying levels is caused by the body's circadian rhythm (body's 24 clock)
        
        cortisol low throughout the day and evening
        
        they increase at 2-4 am and weak just before waking up
        
        the peak is unexplained (speculates that it could be due to not eating for 12 hrs or to prepare for the day's stress)
        
        functions
        
        because it is a glucocorticoid, it is involved with glucose metabolism and comes from the adrenal cortex
        
        cortisol protects the body from hypoglycemia (low blood glucose levels) through its catabolic nature
        
        breakdown metabolic substrates to maintain proper blood glucose levels
        
        the energy can also come from fats and aa when glucose levels are low
        
        cortisol increases glucose levels
        
        how cortisol functions in different tissues
        
        liver
        
        increases gluconeogenesis (produce glucose from non-carbohydrates like fats and aa)
        
        skeletal muscle
        
        decrease protein synthesis
        
        increases protein breakdown
        
        decrease glucose uptake
        
        adipose tissue
        
        decrease lipid synthesis
        
        increase lipolysis (fat breakdown) except in abdomen and cheeks where fat deposit increases
        
        diseases
        
        Cushing's syndrome
        
        caused by an excess of cortisol
        
        symptoms
        
        wasting muscles (causing weakness)
        
        thin skin, resulting in being bruised easily
        
        poor wound healing
        
        fat deposits in cheeks and abdomen, resulting in obesity and a round face (moon face)
        
        depression
  - - - has endocrine tissue
        
        secretes hormones into the blood
        
        has 1 -2 million pancreatic islets (islets of Langerhans)
        
        these islets are 0.1 mm and surround small capillaries
        
        these islets contain 3 types of cells
        
        alpha cells
        
        make up of 25% of all islets
        
        secretes glucagon
        
        beta cells
        
        make up 60% of islets
        
        secrete insulin and amylin
        
        delta cells
        
        make up 10% of islets
        
        secretes somatostatin (IGF-1)
      - has exocrine tissue
        
        secretes chemicals through a duct into the digestive tract
        
        made up of pancreatic acinar cells and ducts
    - - insulin
        
        comes from beta cells
        
        causes cells to take up, store and use glucose
        
        causes blood glucose levels to decrease
        
        secreted when blood glucose levels increase
        
        only a small increase is required to cause the release of insulin
        
        the insulin secreted promotes glucose uptake and storage (storing glucose as glycogen)
        
        virtually all cells respond to insulin
        
        liver, muscle and adipose tissue respond maximally to it
      - glucagon
        
        works oppositely to insulin by increasing blood glucose concentration
        
        is secreted when blood glucose levels drop or when aa levels in blood rise
        
        once secreted in the blood, glucagon stimulates the liver to cause glycogenolysis + gluconeogenesis
        
        glycogenolysis
        
        breakdown of glycogen into glucose
        
        gluconeogenesis
        
        formation of new glucose molecules from nonglucose fuel sources such as aa
        
        ex: during exercise where it can increase by 4-5x
        
        during this time, it is believed that glucagon causes release of fatty acids from fatty tissue as fuel
        
        this release of glucagon is caused by the response of the sympathetic nervous system
        
        this is because fatty acids can diffuse across the muscle membrane unlike glucose
      - somatostatin
        
        also released in the digestive tract by the hypothalamus acting as a growth hormone inhibiting hormone
        
        secreted by delta cells of the pancreas
        
        release in the pancreas occurs when blood glucose levels, blood born fats (fatty acids) or when aa levels increase
        
        all related to food ingestion
        
        primary function is to reduce secretion of both insulin and glucagon
        
        reason for this is not understood but thought to be related to prevent rapid food storage as well as making the food available for longer to the body
    - - blood glucose in a fasted indv (before breakfast) is between 80-90 mg/100ml of blood
        
        after a meal it rises to 120-140 mg/100 ml of blood
        
        this value returns to normal after all the carbohydrates are absorbed with help from insulin
      - in starvation glucagon promotes gluconeogenesis to maintain blood levels at 80-90 mg/ 100 ml of blood
      - constant blood glucose levels is required to use the glucose as fuel for the brain, retina and some cells in the gonads
    - - described as the inability of the pancreas to produce insulin or the inability of the target cells to react to insulin
        
        in both types of diabetes, there is a large decrease in use/uptake of glucose in the cells of the body
        
        this causes a big increase in blood glucose levels well above normal
      - type 1 diabetes
        
        occurs from damage to the insulin-producing beta cells, causing less insulin production
        
        often called juvenile diabetes mellitus as it occurs at around 14
        
        cause is unclear but understood as the immune system destroying the insulin producing beta cells of the pancreas
        
        no insulin means blood glucose levels can reach 300 -1200 mg/100 ml of blood
        
        being unable to use glucose as energy cells rely on aa and fats as fuel
        
        this can have many consequences on the body
        
        increased glucose in urine
        
        increased dehydration due to more glucose in urine
        
        1 more item...
        
        damage to blood vessels which can cause tissue damage throughout the body
        
        1 more item...
        
        severe metabolic acidosis from accumulation of acid from fat breakdown for fuel
        
        1 more item...
        
        depletion of protein storage as proteins are constantly being broken down to be used as energy
      - type 2 diabetes
        
        most common (80-90% of all diabetes)
        
        occurs after 40 and called adult-onset diabetes
        
        caused by cells being unresponsive to insulin, causing glucose levels to rise
        
        this causes more insulin to be release until beta cells are depleted
        
        this explains why there is a decrease in insulin release in later stages of type 2 diabetes
        
        causes people to be obese, but can be controlled through their diet
        
        symptoms are different from type 1 diabetes as insulin is still circulating in the blood
        
        symptoms
        
        increased glucose in urine
        
        increased dehydration
        
        damage to blood vessels
        
        at later stages, similarities in symptoms do show