ENDOCRINOLOGY

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ENDOCRINOLOGY
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INTRODUCTION

• Endocrinology study of the endocrine system
• Encompasses knowledge of the functions of the
  endocrine system, endocrine glands, types and
  functions of hormones especially in the
  regulation of the physiological activities of the
  body

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Functions of the endocrine system

• The endocrine and nervous systems are two
  regulatory systems of the body
• Compared to neural activity, the action of
  hormones is usually slower and prolonged
• The endocrine system mainly controls activities
  that require a longer duration.
• Eg Help in maintaining homeostasis and
  regulation of activities such as the
  concentration of chemicals in body fluids and
  metabolism of lipids, carbohydrates and proteins
• Work closely with the nervous system to help the
  body combat stress
• Assist in the regulation of growth and
  development especially in maturity, sexual
  development and reproduction

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The endocrine system is a complex system

• One endocrine gland can produce multiple
  hormones. A single hormone can be produced by
  more than one endocrine gland.
• A single hormone can have more than one type of
  target cell therefore, more than one effect.
  Also, a single target cell can be influenced by
  more than one hormone.
• Other factors contribute to the complexity of the
  system. The rate of secretion of a hormone can
  vary over time.
• The same chemical messenger can be a hormone or
  neurotransmitter (e.g., norepinephrine).
• Some organs have exclusively endocrine functions.
  Other organs (e.g., testis) have endocrine
  functions and non-endocrine functions.

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Hormone

• Special chemical substances produced and secreted
  by endocrine cells/tissues/glands
• Effective even in small quantities
• Balanced by other hormones
• Can act on cells located far away, nearby or on
  the cell that secretes the hormone
• Helps to regulate the rate of biochemical
  reactions
• Is not influenced or changed by the reactions
  that it controls

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Hormone

• Can be categorized by its solubility
• 1.   Water soluble (hydrophilic) eg peptide and
  protein hormones are transported freely in blood
• Fat soluble (lypophilic) eg steroid hormones and
  prostaglandins are transported in blood by
  binding to plasma proteins
• Can be categorized according to its chemical
  structure
• 1. Acid amino derivatives (amines and secreted by
  adrenal medulla with the main aa being tyrosine)
• Peptide hormones (small peptides, polypeptides,
  glycoproteins)
• Lipid derivatives (steroid hormones and
  eicosanoids)
• (steroid hormones are secreted by the adrenal
  cortex and gonads)

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•  Examples of hormones
• 1. Protein hormones Growth Hormone (GH),
  prolactin and insulin
• 2. Glycoprotein hormones Follicle Stimulating
  Hormone (FSH), Luteinizing Hormone (LH), Thyroid
  Stimulating Hormone (TSH) and Parathyroid Hormone
  (PTH)
• 3. Polypeptide hormones oxytocin, calcitonin,
  glucagon
• 4. Acid amino derivative hormones adrenaline
  (epinephrine), noradrenaline (norepinephrine),
  melatonin, dopamine, thyroid hormones
• 5. Lipid/steroid hormones testosterone,
  estrogen, corticosteroids, cortisol
• 6. Fatty acid hormones/eicosanoids thromboxane,
  leucotriene and prostaglandins

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The mechanisms of hormone synthesis, storage, and
secretion vary according to the class of hormone

• Peptide hormones have precursors called
  preprohormones made on ribosomes of the
  endoplasmic recticulum (ER). Are converted to
  prohormones and active hormones in the Golgi
  complex. The Golgi complex concentrates these
  hormone into secretory vesicles which are then
  eleased from endocrine cells by exocytosis
• Cholesterol is the common precursor for all
  steroid hormones. A series of enzymatic steps
  modify this molecule into a different hormone in
  a specific endocrine cell. Only the precursor
  (cholesterol) is stored. The lipid-soluble
  hormone is not stored
• The amine hormones are made from tyrosine. These
  hormones are stored until they are secreted

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Regulatory feedback mechanisms

• Hormones are secreted in a fixed amount to
  maintain homeostasis, i.e., not secreted
  continuously
• Why? Any changes in the bodys physiology will be
  detected by the brain (main control center) where
  actions has to be taken to maintain homeostasis
• Therefore secretion of hormones are dependant on
  a feedback mechanism
• This regulatory feedback mechanism is either
  positive or negative, long loop or short loop
• Example of a positive and negative feedback
  mechanism is the regulation of the functions of
  the female reproductive system
• Example of a long loop and short loop feedback
  mechanism is the regulation of the body systems
  under stressful conditions

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• Interactions of hormones with target cells
• What are target cells?
• Target cells are
• cells that possess a receptor that is compatible
  to the hormone and is located either on the
  plasma membrane surface or in the cytoplasm or
  nucleus
• influenced by certain hormones

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• Hormones that combine with receptors will
  influence the rate of cell physiological
  processes
• Down regulation is a decrease in the number of
  receptor molecules in target cells
• Up regulation is an increase in receptor
  molecules of target cells

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• Types of hormone receptors
• Receptors that are located on the membrane or
  membrane surface will bind to hydrophilic
  hormones or hormones that have a large molecular
  weight
• Receptors that are located intracellular (in the
  cell) will bind to lypophilic hormones

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Mechanism of hormone action

• Act by binding to special receptors on target
  organs
• A hydrophilic hormone binds to the target cell
  surface and activates a second-messenger system
• Eg Protein hormones will bind to receptors on
  the surface of the plasma membrane of the target
  cell
• require a messenger i.e., second messenger e.g.,
  cAMP (cyclic adenosine monophosphate) present in
  the extracellular fluid to trigger a biologic
  reaction
• eg., insulin

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• A lipophilic hormone stimulates a gene, promoting
  protein synthesis
• EgSteroid hormones have a receptor in the cell
  and can diffuse freely into cells because it is
  lypophilic
• After binding with the cytoplasmic receptors in
  the target cells, it will trigger a physiological
  reaction
• eg., estrogen

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Mechanism of hormone action for protein hormones
(hydrophilic)

• Hydrophilic hormones secreted by endocrine glands
• ?
• Travel freely in blood vessels until reach target
  organs
• ?
• Bind with receptor on surface of plasma membrane
• ?
• Hormone-receptor complex stimulates G protein
• ?
• G protein connects this complex to adenyl cyclase
  enzyme in the inner surface of the cell

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• Activated adenyl cyclase converts ATP to cAMP
• ?
• cAMP activates protein kinases
• ?
• Protein kinases trigger a cascade of enzyme
  reaction
• ?
• Causes cells to undergo certain functions
• i.e., release of energy from hepatic cells
• ?
• After cells have completed their physiological
  functions, cAMP is deactivated by
  phosphodiesterases
• ?
• Location of receptor on the plasma membrane
  returns to its origin and ready to receive new
  hormones

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Plasma membrane
First messenger, usually an extracellular chemica
l messenger
G protein intermediary
ECF
Adenyl cyclase
ICF
(Converts)
Receptor
Second messenger
Binding of extracellular messenger to
receptor activates a G protein, the a subunit of
which shuttles to and activates adenyl cyclase
(Activates)
(Phosphorylates)
(Phosphorylation induces protein to change shape)
phosphate
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Mechanism of steroid hormones (lypophilic)

• Lypophilic hormones are secreted
• ?
• Transported in blood by binding to plasma
  proteins
• ?
• Released by plasma proteins on reaching target
  cells
• ?
• Diffuses through plasma membrane and binds to
  receptor inside cytoplasm
• ?
• Hormone receptor complex enters cell nucleus and
  binds to cell DNA
• ?
• Triggers DNA transcription and produces mRNA
• ?
• Directs protein synthesis
• egbreast development under estrogen influence
  and development of dense muscular mass under
  testosterone influence

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Plasma membrane
Cytoplasm of target cell
Nucleus
H Free lypophilic hormone R Lypophilic
hormone receptor
HRE Hormone response element mRNA Messenger
RNA

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Hormone excretion

• Hormones will be excreted after completing its
  functions
• Hydrophilic hormones have a short life span while
  lypophilic hormones have a longer life span
• Life span of hormones is termed half-life

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Rate of hormone excretion

• Rate of hormone excretion is dependant on the
  plasma concentration of that hormone which is
  regulated by changes in its rate of secretion
  i.e.,
• Hormones rate of secretion by the endocrine
  gland (major factor for all hormones)
• Its rate of metabolic activation (for a few
  hormones)
• Its extent of binding to plasma proteins
  (lipophilic hormones)
• Its rate of metabolic inactivation and excretion
  (for all hormones)

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Types of hormone excretion

• 1. Rapid excretion through the kidney into
  urine or the liver into bile
• 2. Metabolism - destroyed by enzymes in the
  blood, liver, kidney, lungs and target cells
• 3. Active transport some hormones are
  transported into cells and reuse as hormone
  substance or neurotransmitter
• 4. Conjugation substances like acid sulphates
  and glucoronic acids will bind to hormones in the
  liver and render it less active as a hormone and
  increase its rate of excretion into urine or bile

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Plasma
Hormone bound to plasma proteins
Endocrine gland
Binding (lipophilic hormones)
Secretion
Free, biologically active hormone
Activation (some hormones)
Metabolism in liver or other tissues
Target cells
Inactivation
Physiologic response
Excretion in urine
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Hormone lifespan

• Hormone lifespan can be prolong by
• Protection from rapid excretion by binding to
  plasma proteins eg., lypophilic hormones
• Protection from proteolytic enzymes in the
  circulatory system by having a carbohydrate
  component in their chemical structure eg.,
  glucoprotein hormones

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Hormone interactions

• Four types of interactions exist
• Antagonistic interaction is opposite each other
  eg calcitonin and parathyroid hormone
• Synergistic hormones interact so that the end
  result will be more meaningful as compared to if
  only one hormone is functioning/several hormones
  complement each other and combine effects eg
  stimulation of mammary glands development by
  prolactin, estrogen, progesterone and growth
  hormone
• Permissive a pattern of interaction whereby one
  hormone must be present in sufficient amounts for
  the full effect of another hormone to occur. eg
  adrenaline needs thyroid hormones for energy
  production
• Integrative an interaction whereby many
  hormones regulate the different body
  physiological systems
• eg calcitriol and PTH effects on tissues
  involved in calcium metabolism

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Other hormones

• Leukotrienes, together with prostaglandins and
  other related compounds, are derived from 20
  carbon (eicosa) fatty acids that contain double
  bonds (enoic), hence this group of substances is
  called the eicosanoids.
• The name leukotriene derives from the original
  discovery of these substances in white blood
  cells (polymorphonuclear leucocytes) and the fact
  that they all have in common 4 double bonds
  (hence the 4 subscript), 3 of which are in a
  conjugated triene structure.
• Leukotrienes do not exist preformed in cells

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• They are formed from the breakdown of arachidonic
  acid, a polyunsaturated 20 carbon fatty acid.
• In its esterified form, arachidonic acid is bound
  to the phospholipids of the cell membranes
• Both immunological and non-immunological stimuli
  can release arachidonic acid from membrane
  phospholipids by activating phospholipase A2
• The glucocorticosteroid drugs can inhibit
  phospholipase A2 and thereby decrease the
  production of all the leukotrienes and hence
  leukotriene-mediated responses

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Endocrine disorders

• Due to hyposecretion or hypersecretion of a
  hormone.
• Factors producing hyposecretion include heredity,
  dietary deficiency, immunologic factors, and
  disease processes.
• Hyposecretion can be primary or secondary (due to
  the deficiency of the hormones tropic hormone).
• Replacement therapy of a hormone can often
  successfully treat the conditions from
  hyposecretion.
• Hypersecretion of a hormone can also be primary
  or secondary.
• Factors producing hypersecretion include tumors
  on the endocrine gland and immunologic factors.
• Endocrine dysfunction can also arise from the
  unresponsiveness of target cells to a hormone.

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Hormone release

• From hypothalamus to anterior pituitary
• releasing or inhibiting hormones from the
  hypothalamus are secreted into the HHP tract to
  the anterior pituitary. Specific hormones from
  the AP are then secreted into the same blood
  vessels to be transported to target cells

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• Therefore robust control systems must be present
  to prevent over or under-secretion of
  hypothalamic and anterior pituitary hormones.
• A prominent mechanism for control of the
  releasing and inhibiting hormones is negative
  feedback

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Hormone release

• 2. From hypothalamus to posterior pituitary
• Neurohormones from posterior pituitary glands are
  produced by neurosecretory cells whose cell
  bodies are located in the hypothalamus
• These axons from the cell bodies enters the
  infundibulum of the posterior pituitary gland
• Gives rise to a nerve tract called
  Hypothalamic-Hypophyseal Tract (HH)

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Hormone release

• neurohormones enters axons and are stored in the
  shape of small secretory vesicles
• Action potentials from the neurone cell bodies in
  the hypothalamus travels down the axons until
  they reach the axon terminals in the posterior
  pituitary glands via the HH tract
• These action potentials causes neurohormone
  release
• These neurohormones then enters the blood stream

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Hypothalamic hypophyseal portal veins
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Pituitary Gland

• Anatomy of the pituitary gland
• The pituitary gland is as large as a pea, and is
  located at the base of the brain
• The gland is attached to the hypothalamus by
  nerve fibers
• The pituitary gland itself consists of three
  sections
• the anterior lobe (pars tuberalis)
• the intermediate lobe (pars intermedia)
• the posterior lobe (pars distalis)

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Pituitary gland

• The anterior pituitary (adenohypophysis) is a
  classical gland composed predominantly of cells
  that secrete protein hormones
• The posterior pituitary (neurohypophysis) is not
  really an organ, but an extension of the
  hypothalamus
• Composed largely of the axons of hypothalamic
  neurons which extend downward as a large bundle
  behind the anterior pituitary
• It also forms the pituitary stalk, which appears
  to suspend the anterior gland from the
  hypothalamus

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Anatomy of the pituitary gland

• Each lobe of the pituitary gland produces certain
  hormones
• anterior lobe
• growth hormone (GH) (non-tropic hormone)
• prolactin (non-tropic hormone)
• ACTH (adrenocorticotropic hormone)
• TSH (thyroid-stimulating hormone)
• FSH (follicle-stimulating hormone)
• LH (luteinizing hormone)

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Anatomy of the pituitary gland

• intermediate lobe
• melanocyte-stimulating hormone (non-tropic
  hormones)
• posterior lobe
• ADH (antidiuretic hormone)/vasopressin
• Oxytocin
• Tropic hormones their target cells are other
  endocrine glands

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• How is it possible for the anterior pituitary
  gland to produce so many different hormones?
• Because the tissues are so specialized
• They contain three types of cells which can be
  distinguished by staining
• Red stained cells/acidophils will produce GH and
  PRL
• Blue stained cells/basophils will produce TSH,
  FSH, LH, MSH and maybe ACTH
• Unstained cells/chromophobe) which is a variation
  of both acidophils and basophils may also produce
  ACTH

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Functions of pituitary hormones
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• GROWTH HORMONE (GH)
• Somatotropin. Effective on all body sections
  involved in growth
• Have a dramatic effect on the growth rate of
  children and adolescents where it increases
  tissue mass and stimulates cell division
• Its secretion is controlled by GH-RH and GH-IH
  from the hypothalamus. This hormone is released
  in a pulsatile rhythm.

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• Functions of GH
• maintains the epiphyseal discs at long bones
• stimulates the rate of growth by increasing RNA
  development that will promote rate of protein
  synthesis
• decreases protein denaturation
• promotes use of fat for energy by storing CHO
• changes body composition to have more muscle
  mass as compared to fat deposition

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• If too much GH is secreted at the end of the
  adolescent stage, gigantism will occur where the
  height will reach 7 to 8 feet tall
• If less GH is secreted at a young age, then a
  premature closure at the epiphyseal discs occur
  and the body will stop growing therefore causing
  a condition called cretinism or dwarfism
• If normal development has stopped but GH is still
  secreted, then a condition called acromegaly
  occurs where the bones at the skull, hands and
  feet thickens
• Too much GH secreted will cause hyperglycemia,
  because the beta cells of the pancreas that
  secretes insulin are stimulated causing diabetes
  mellitus

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Acromegaly
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Gigantism
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Adrenocorticotropic hormone (ACTH)

• Stimulates the adrenal cortex gland to synthesis
  and release glucocorticoids
• ACTH secretion is regulated by (C-RH) or
  corticotrophin from hipothalamus.
• C-RH is regulated by a feed-back mechanism system
  that is influenced by stress, the homone insulin,
  interleukin and other hormones

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Melanocyte Stimulating Hormone (MSH)

• Real function unknown
• May play a role in the darkening of skin because
  skin will look pale without MSH.
• MSH release is regulated by two hormones from the
  hipothalamus that is MSH-RH and MSH-IH
• MSH is secreted by the pars intermedia during the
  fetal stage, during childhood and to pregnant
  women and also in some diseases. MSH is usually
  not detected in mature human blood

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Hyperpigmentation
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Thyroid stimulating hormone (TSH)

• Stimulates the synthesis and secretion of the
  hormones thyroxine and triiodothreoinine. Goiter
  occurs when the thyroid gland enlarges due to too
  much TSH stimulation
• TSH secretion is controlled by T-RH from
  hipothalamus.
• T-RH release depends on the concentration of TSH
  and thyroid hormones in the blood, metabolic rate
  of the body and the surrounding temperature

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Anti-diuretic hormone (ADH)

• Vasopressin.
• Functions in urine production and assist in
  regulating fluid balance in the body
• Target organ is the kidney.
• ADH increases kidney tubules permeability to
  water so gt water is reabsorbed into the body and
  not excreted as urine
• If ADH lt secreted, a lot of water will be lost up
  to 23 liters daily causing a condition called
  diabetes insipidus

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• Secretion of ADH will increase in a response to
  emotional or physical stress, plasma osmotic
  pressure increases, decreased extracellular fluid
  volume due to high blood loss, heavy exercise and
  intake of nicotine or barbiturates
• Secretion of ADH will decrease as a response to
  low plasma osmotic pressure, increased
  extracellular fluid volume and a high level of
  alcohol in blood

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PROLACTIN (PRL)

• Have two functions in women. Along with estrogen,
  they stimulate the development of the ductal
  system in the mammary glands during pregnancy.
• Prolactin also synthesize milk after parturition
• Prolactin release can be inhibited by (P-IH) or
  dopamine from hipothalamus. This inhibition is
  high in non-pregnant women or non-breastfeeding
  women. This inhibition is lifted during
  pregnancy.

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Luteinizing Hormone(LH)

• Also known as Interstitial Cell Stimulating
  Hormone (ICSH) in the male reproductive system
• Is a gonadotrophic hormone that stimulates
  ovulation
• Stimulates progesterone and a little bit of
  estrogen release from the corpus luteum
• Target cells in male is the Leydig cells
• Release of LH is dependant on Gn-RH from the
  hipothalamus which is regulated by a feedback
  mechanism involving progesterone, estrogen and
  testosterone levels in the blood

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Follicle Stimulating Hormone (FSH)

• Also a gonadotropic hormone.
• Stimulates follicular growth in the ovary at each
  menstrual cycle and also stimulates cells in the
  testes to produce spermatozoa
• Stimulates the follicles to secretes estrogen and
  the Gn-RH from the hypothalamus is the regulatory
  factor for FSH release
• How do FSH and LH affects both the male and
  female reproductive system?

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• Both hormones stimulate and gave the same
  response to two different tissues (testes and
  ovaries) because both organs/gonads have the same
  embryonic origins
• FSH is related to the production of sex cells for
  both males and females while LH is related to the
  release of sex hormones

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Oxytocin

• Stimulates smooth muscle contractility at the
  myometrium of the uterus before parturition
• Uterus will be sensitive to oxytocin at the end
  of pregnancy
• Release of oxytocin increases when estrogen
  increase close to parturition

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• Will also stimulate myoephitelial cells
  surrounding the ductal region of the breast to
  ejects milk during lactation
• Nipple stimulation by the baby will send a nerve
  impulse to the hipothalamus to cause the
  posterior pituitary to release oxytocin
• Works together with prolactin throughout
  lactation period

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Thyroid glands

• Located in front of the trachea on the neck
  region
• Made up of two lobes connected to each other by a
  bridge (isthmus).
• Possess a very efficient circulatory system
  (80-100 ml blood/min)  
• Made up of thousands of spherical gelatinous sacs
  where the thyroid hormones are kept
• Two types of cells follicular cells (abundance)
  and parafollicular cells (bigger but less).
• Follicular cells synthesize and secretes
  thyroxine (tetraiodotreionine T4) and
  triidothreoinine (T3)
• Made up of iodine and thyroxine
• Parafollicular cells synthesize and secretes
  calcitonin

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• lt thyroid hormones hypothyroidism, cretinism
  (if this happens during prenatal development,
  mental disability and abnormal growth of bones
  and muscles occurs
• gt thyroid hormones hyperthyroidism, goitre

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• Regulation of thyroid hormones
• The secretion of thyroid hormones is regulated by
  TSH
• TSH is secreted if lt thyroid hormones in the
  blood, when too cold or under stress or pregnancy
• TSH is inhibited when the thyroid hormone levels
  are gt in the blood.
• The ve and ve feedback mechanism control
  the secretion of thyroid hormones

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Parathyroid glands

• Pea-shaped and embedded in the posterior lobe of
  the thyroid gland.
• Each lobe will have a pair of parathyroid glands
• Due to its small size, this gland was only
  discovered in 1850. Before its discovery, it is
  usually accidentally removed during thyroid
  surgery and patients dies afterwards.
• Consists of principal or chief cells which
  secretes parathyroid hormone or parathormone and
  oxyphilic cells of unknown function
• Hormone secretion is dependent on the
  concentration of calcium and phosphate ions in
  the blood

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Parathyroid hormone (PTH)

• Increases calcium ions in the blood whenever
  calcium concentration falls below normal
• Interacts antagonistically with calcitonin
• Increases Ca in the blood by stimulating
  osteocyte activity in destruction of bone tissue
  and releasing the Ca into the blood
• Stimulates Ca and PO4 absorption in the small
  intestines and reabsorption of Ca and PO4 by the
  kidneys
• Decreases the concentration of PO4 in the blood
  by inhibiting reabsorption in kidney and
  increasing its excretion into urine

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Calcium homeostasis
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Thymus gland

• A bi-lobe lymphoid organ located at the back of
  the sternum on the anterior mediastinum.
• Cortex (high lymphocytes) and medulla (less
  lymphocytes) but consists of a branch of thymic
  corpuscle cells whose function is unknown
• Supplied by blood vessels but less nerve fibers
• Maximum efficiency during adolescence hood but
  becomes small during adulthood
• Secretes thymosin and its release is dependent on
  the demand for T lymphocytes and antibodies by
  the body
• Functions in preprocessing of T cells and
  development of B cells to plasma cells to produce
  antibodies

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Adrenal gland

• Triangular shaped
• Located on the left and right kidneys
• Two endocrine glands that differs in both hormone
  production and target cells
• Inner part - medulla which consists of secretory
  cells originating from embryonic ectodermal
  tissues and ganglia from the symphatetic nervous
  system branch of the autonomic nervous system
• Contains two populations of cells that secretes
  adrenaline and nor-adrenaline

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• Outer part - cortex which is bigger and produces
  steroid hormones glucocorticoid,
  mineralocorticoid and androgens
• Secretion of adrenaline and nor-adrenaline is
  dependent on the bodys reaction to stress
• Secretion of glucocorticoids and androgens are
  controlled by ACTH
• Secretion of mineralocorticoid (aldosterone)
  depends on the concentration of water and ions in
  the body

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• Glucocorticoids
• Functions
• 1. Stimulates gluconeogenesis (synthesize glucose
  from liver from non-CHO sources e.g. amino acids
  and fatty acids
• 2. Stimulates glycogenesis (process to produce
  glycogen from CHO stores kept in the liver)
• 3. Anti-inflammatory agent, effective on growth
  and can decrease the effects of physical and
  emotional stress
• Glucocorticoid family - cortisol
  /hydrocortisone, corticosterone dan cortisone
  where cortisol is responsible for 95 of
  glucocorticoid activity .

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• Mineralocorticoids
• Functions
• - regulate the concentration of water and ions
  e.g Na and K.
• - The main hormone aldosterone functions in
  stimulating Na retention by the kidney and K
  excretion into urine
• Androgen
• secreted in small amounts by sexual hormones
• Functions its importance is unknown

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•  
• Adrenaline,nor-adrenaline, dopamine
  catecholamines
• Adrenaline and nor-adrenaline produces an effect
  that is similar to stimulation by the symphatetic
  nervous system
• Functions to accelerate the energy consumption by
  body cells and to mobilized energy stores for
  body systems utilization
• Is secreted in body response to stress or flight
  or fight response
• gt adrenaline is secreted as compared to
  nor-adrenaline. The half-life is short., only 3
  minutes then it will be deactivated by hepatic
  enzymes

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• Adrenaline causes vasoconstriction and
  vasodilation of certain blood vessels to allocate
  more blood to the brain and muscles
• Digestive process stops, blood pressure gt heart
  rate gt, clotting time lt, respiration rate gt and
  bronchioles dilate
• Hepatic enzymes are activated to release glucose
  from glycogen stores (glycolysis) for instant
  energy to cells that needs them
• Adrenaline functions for energy consumption

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Summary of control of Fight or Flight reaction

• Adrenaline and nor-adrenaline are secreted
• Vasoconstriction/vasodilation of certain blood
  vessels
• gt blood supply to brain and muscles
• Blood pressure gt, Heart rate increases gt
• Blood clotting time lt, Rate of breathing gt
  Glycolysis gt, Digestive process stops, Urine
  output lt, Pupils dilate
• Increase in energy consumption
• Secretion stops after 3 minutes and condition
  returns to normal

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Running from tsunami
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Digestive Hormones

• Gastrin
• Cholescystokinin
• Secretin

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• Gastrin is a hormone that stimulates secretion of
  gastric acid by the stomach. It is released by G
  cells in the stomach and duodenum.
• Secretin is a peptide hormone produced in the S
  cells of the duodenum in the crypts of
  Lieberkühn. Its primary effect is to regulate the
  pH of the duodenal contents via the control of
  gastric acid secretion and buffering with
  bicarbonate.
• Cholescystokinin is a peptide hormone responsible
  for stimulating the digestion of fat and protein.
  Previously called pancreozymin, this hormone is
  secreted by the duodenum, and causes the release
  of digestive enzymes and bile from the pancreas
  and gallbladder, respectively.

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Kidney

• Kidney is basically an excretory organ, but it is
  also an endocrine gland
• Secretes three types of hormones- calcitriol,
  erythropoeitin and rennin
• Secretion of calcitriol is dependant on PTH
  production
• Secretion of erythropoeitin depends on the amount
  of RBC in the circulation
• Secretion of rennin depends on fluid and ionic
  concentration

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• CALCITRIOL,ERITHROPOEITIN AND RENNIN
• Calcitriol
• Is synthesize and secreted as a response to PTH
  secretion
• Also dependant on vitamin D3 (cholecalciferol).
• Functions to stimulate Ca and PO4 absorption from
  the digestive tract
•  Erythropoeitin
• Stimulates RBC production by gt Haemoglobin (Hb)
  synthesis
• and release of RBC from bone marrow
• Rennin
• Functions like an enzyme when secreted by cells
  of the juxtaglomerular apparatus of the kidney
  into the blood vessels.
• Rennin changes angiotensinogen (from the liver)
  to angiotensin I.  

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• Angiotensin I changes to angiotensin II by
  angiotensin converting enzymes in the capillaries
  of the lungs. Angiotensin II functions to
• 1) stimulates aldosterone production from the
  adrenal cortex and ADH secretion from the post.
  pituitary
• 2) stimulates thirst so we consume more fluids
  to increase blood volume
• 3) triggers arteriole contraction so that blood
  volume increases and this effect is 4-8 X gt
  effects by noradrenaline

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• The rennin-angiotensin I-angiotensin II system
  influences blood pressure and volume, salt intake
  and salt-fluid balance
• Rennin is secreted when there is a symphatetic
  stimulation and lt blood flow to the kidneys due
  to lt blood volume, blood pressure or both

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Heart

• Basically the heart is the most important organ
  in the circulatory system
• The heart however also contains secretory cells
  located at the atrium that synthesize, store and
  secretes a peptide hormone called atrial
  natriuretic peptide (ANP).
• ANP secretion depends on the salt concentration
  in the body

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• ATRIAL NATRIURETIC PEPTIDE
• Is secreted continuously but in a small amount in
  the circulation
• The secretion when gt salt in the body, blood
  pressure gt which stimulate stretch receptors in
  the atrium or when blood pressure gt significantly
• Target cells are the blood vessels, kidney and
  adrenal gland

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• Functions
•   1) stimulates Na and air excretion by kidneys
• 2) inhibit rennin release and the secretion of
  hormones (ADH and aldosterone) involve in water
  retention
• 3) lt thirst and inhibit the action of
  angiotensin II or nor-adrenaline on arterioles.
  The relaxation of blood vessels will help to lt
  blood pressure and cardiac muscles stretching on
  the atria

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Pineal gland

• A small granule located at the at the
  diencenphalon at the inner part of the cerebral
  hemisphere on the posterior part of the third
  ventricle
• Contains neuron, glial cells and secretory cells
  called pinocytes
• Synthesize the hormone melatonin from serotonin
  molecules which is a neurotransmitter.
• Melatonin secretion is dependant on light
  availability

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• How? This is because the collateral nerve from
  the vision pathway enters the pineal gland and
  this influence the melatonin production rate
• Melatonin is secreted more at night as compared
  to daytime

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• Melatonin
• Is secreted at a constant rate every night
• Production is inhibited by light
• lt secretion of melatonin causes drowsiness
  because the sleep cycle is disturbed
• Important to maintain biological rhythm and
  light-dark cycle
• In mammals, melatonin slows sperm, ovum and
  reproductive organ maturity by lt rate of Gn-RH
  secretion
• Melatonin may also slow down human sexual
  maturity (levels of melatonin in the blood falls
  at puberty. If there is a tumour at the pineal
  gland, loss of melatonin will cause premature
  puberty to children

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• An important antioxidant that protects CNS from
  free radicals NO or H202 produced by active
  nervous tissues
• Activity of pineal gland is cyclic i.e., plays a
  role in the circadian rhythm (daily changes in
  physiological process that follows the same
  pattern)
• gt melatonin secretion during the dark may be the
  primary cause for a condition called seasonal
  affective disorder (SAD).
• SAD changes to behavior, nutritional intake and
  sleep patterns occurring to people living at high
  altitudes during the winter when amount of light
  is shorter

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Pancreas

• Important in the digestive process
• Elongated and fleshy and about 12 15 cm long
• Located posterior to the stomach
• An exocrine and endocrine organ
• The exocrine component is involved in the
  digestive process
• The endocrine part is located at the Islets of
  Langerhans which is about 200,000 to 2 million
  islets in an adult pancreas

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• The islets contains alpha cells (glucagon), beta
  cells (insulin), delta cells (somatostatin) and F
  cells (pancreatic polypeptide)
• The secretion of glucagon and insulin depends on
  glucose concentration in the blood
• Secretion of somatostatin depends on GH
• Secretion of pancreatic polypeptide depends on
  the release of digestive enzymes from the
  pancreas

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• GLUCAGON 
• Peptide hormone ( hyperglycemic hormone).
• Function - stimulate glycogenolysis (stimulate
  the liver to convert glycogen to glucose whenever
  hypoglycemia occurs
• Also stimulates gluconeogenesis, lypogenolysis
  (release of fatty acids and glycerol from adipose
  tissues) and gt cAMP concentration from ATP in
  hepatocyes 
• INSULIN
• Peptide hormones (hypoglycemic hormone)
• The first hormone that has its full chemical
  structure identified by Frederick Sanger in 1955.
  
• Function gt glucose uptake into cells, gt
  conversion of glucose to glycogen (glycogenesis)
  to be stored in the liver  

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• gt glucose transport into cells which will gt CHO
  metabolism and lt blood glucose concentration
  (hypoglycemic)
• gt amino acid transport into cells to gt protein
  synthesis
• gt conversion of glucose to fatty acids
  (lypogenesis).
• Act antagonistically with glucagon because it lt
  glucogenolysis and gluconeogenesis.
• If gt insulin secreted, hypoglycemia occurs
• If lt insulin secreted, diabetes mellitus occur
  and will cause hyperglycemia and excess glucose
  will be excreted by the kidneys into urine
•  

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• Why do diabetics have to take injectable insulin
  rather than oral insulin? This is because insulin
  molecules are so small and if taken orally, will
  be destroyed by the gastric juices in the
  stomach.
• SOMASTOSTATIN
• A GH-IH like hormone that can inhibit insulin and
  glucagon secretion
• PANCREATIC POLYPEPTIDE
• Regulate the secretion of digestive enzymes from
  the pancreas

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Testis

• Part of the male reproductive tract
• Produces testosterone from the interstitial cells
  of Leydig and inhibin from Sertoli cells

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• TESTOSTERONE
• Functions
• Stimulate sperm production together with FSH and
  LH
• Growth, development and maintanance of male
  sexual organs
• Stimulate development and maintains male sexual
  libido
• Responsible for development of male secondary
  sexual characteristics incl. voice deepening,
  body hair growth, muscle mass and others

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• Production of testosterone depends on the
  testosterone levels in blood
• If increase, will send negative feedback
  mechanism to pit. ant. to inhibit LH release
• INHIBIN
• Function
• Helps in sperm production
• If amount of sperm gt 20 million cells/ml, inhibin
  will send a negative feedback mechanism to the
  ant pit to inhibit FSH release
•  

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Ovary

• Part of female reproductive system
• Produces estrogene (follicles), progesterone
  (corpus luteum), inhibin (follicle), relaxin
  (corpus luteum) during pregnancy
• Uterus produces prostaglandin F 2 ?

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• ESTROGENE 
• Function
• Regulate menstrual cycle
• Development of the mammary glands
• Development of female secondary sexual
  characteristics (enlargement of breasts, gt
  adipose tissue at the buttock, growth of body
  hairs, and maintanance of female sexual organs).
• Hormone that stimualates sexual desire in women

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• PROGESTERONE
• Function
• Maintains pregnancy
• Regulate menstrual cycle
• Development of mammary glands and placental
  formation during pregnancy
• Pregnancy hormone

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• RELAXIN
• Function
• Important during parturition
• Softens cervix by causing ligament dilation at
  the symphisis pubis to facilitate delivery
• Helps in development of mammary glands during
  pregnancy
• During early pregnancy, secretion of relaxin
  depends on LH influence
• At the end of pregnancy, relaxin is secreted due
  to the influence of human chorionic gonadotrophin
  released by the uterus. Relaxin secretion stops
  after parturition

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• PROSTAGLANDIN F2?
• Function
• Kills corpus luteum (luteolytic) when no
  fertilization occurs and no embryonic
  implantation
• Can cause eruption of spiral arteries in the
  uterus and endometrium to contract causing
  menstrual cramps
• Can erode sperm plasma membrane causing
  capacitation during sperm transport in the female
  reproductive tract