Chapter 9 The Endocrine System

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Chapter 9 The Endocrine System

• Biology 112
• Tri-County Technical College
• Pendleton, SC

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Hormones are flowing

• Hormones are chemical substances secreted into
  extracellular fluid that regulate activity of
  other cells
• Hormones circulate to all organs but affect ONLY
  certain tissue cells/organs referred to as its
  TARGET CELLS/ORGANS
• Target MUST have specific protein receptors on
  its plasma membrane or interior to which hormone
  can attach

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Hormones, cont.

• Reproduction, growth development, bodys
  defenses against stressors, electrolyte, water,
  nutrient balance of blood, regulating metabolism
  energy balance
• Typically one or more of following occur as
  result of hormone action
• changes in PM permeability/electrical state
• synthesis of proteins or regulatory molecules
• activation/inactivation of enzymes
• stimulation of mitosis/meiosis

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Getting there

• Steroid hormones able to diffuse across PM
• Nonsteroid hormones require membrane receptors
  and utilize signal-transduction mechanism (second
  messengers)
• One of three mechanisms responsible for
  stimulating endocrine gland
• HORMONAL
• HUMORAL
• NEURAL

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Hormonal Action, Visual
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Stimulation, Visual
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Been theredone that

• Hormonal secretion triggered by some
  internal/external stimulus
• Rising hormone levels inhibit further hormone
  release even while promoting responses in target
  organs
• WOW!!! Negative feedback model again
• End product controls the rate of the reaction
  or event

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Endocrine Glands

• Endocrine glands (ductless) release their
  secretions into blood or lymph
• Endocrine glands have a very rich blood supply
• Hypothalamus, pituitary, thyroid, parathyroid,
  adrenal, pineal, thymus, pancreas, and gonads
  (testes/ovaries)

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Location, Visual
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Pituitary Gland

• Pituitary gland about the size of a grape and
  hangs by a stalk from inferior surface of
  hypothalamus of the brain
• surrounded by turks saddle of sphenoid bone
• Has two functional lobes
• Anterior pituitary arises from glandular tissue
• Posterior pituitary arises from nervous tissue
• Anterior hormones growth hormone (GH), prolactin
  (PRL), follicle-stimulating (FSH), luteinizing
  (LH), Thyroid stimulating (TSH) and
  Adrenocorticotropic (ACTH)

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Pituitary, cont.

• Growth hormone and prolactin exert their major
  effects on nonendocrine targets
• FSH, LH, TSH, and ACTH are all TROPHIC hormones
• Trophic hormone is hormone that regulates the
  activity of another ENDOCRINE gland
• All anterior pituitary hormones are
  proteins/peptides act through 2nd messengers
  are regulated by hormonal stimuli, and operate
  via negative feedback mechanism (in most cases)

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Anterior Pituitary, Visual
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Growth Hormone

• GH is protein-sparing anabolic hormone causing
  amino acids to build into proteins
• Stimulates MOST target cells to grow in size and
  divide
• Causes fats to be broken down for energy
• Spares bodys supply of glucose thereby helping
  to maintain blood sugar homeostasis

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Pituitary Abnormalities

• Hyposecretion of GH during childhood leads to
  pituitary dwarfism
• body proportions fairly normal but person is
  living miniature (adult height 4 feet)
• Hypersecretion during childhood leads to
  gigantism
• individual becomes extremely tall (8-9 feet)
• If hypersecretion occurs after long bone growth
  ended acromegaly
• lower jaw and bony ridges under eyebrow enlarge
  as does hands and feet thickening of soft tissue
  leads to coarse/malformed facial features
• Most hypersecretion of endocrine glands caused by
  tumors of affected gland

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Prolactin

• Abbreviated as PRL
• Protein hormone whose only known target in humans
  is the breast
• After childbirth, it stimulates and maintains
  milk production by mothers breasts
• Its function is males is NOT known

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Same song, different verse

• Adrenocorticotrophic hormone ACTH
• Regulates activity of the cortex portion of the
  adrenal gland
• Thyroid-stimulating hormone TSH
• TSH also known as thyrotropic hormone (TH)
• Influences growth and activity of the thyroid
  gland

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Follicle Stimulating Hormone

• Abbreviated as FSH
• Regulates activity of gonads (ovaries/testes)
• In females, FSH stimulates follicle development
  in ovaries
• As follicles mature, they produce estrogen and
  eggs are readied for ovulation
• In males, FSH stimulates sperm development by the
  testes

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Luteinizing Hormone

• Abbreviated LH
• In females, LH triggers ovulation of egg from
  ovary
• Also causes ruptured follicle to become corpus
  luteum
• LH then stimulates corpus luteum to produce
  progesterone and some estrogen
• In men, LH is referred to as interstitial
  cell-stimulating hormone (ICSH)
• stimulates testosterone production by
  interstitial cells

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Pituitary and Sterility

• Hyposecretion of FSH or LH leads to sterility in
  both males and females
• Hypersecretion does NOT appear to cause any
  problem(s)
• Some drugs used to produce fertility stimulate
  release of FSH and LH
• Multiple births fairly common after their
  administration

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Anterior Pituitary/Hypothalamus

• Pituitary used to be called master gland
• Release of pituitarys hormones controlled by
  releasing and inhibiting hormones produced by
  hypothalamus
• Hypothalamus releases these regulatory hormones
  into portal circulation which connects blood
  supply of hypothalamus with that of anterior
  pituitary

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Posterior Pituitary

• Posterior pituitary (neural tissue) STORES two
  hormones produced by hypothalamus
• Oxytocin and antidiuretic hormone (ADH)
• Both are peptide hormones
• Produced in hypothalamus
• Transported along axons of hypothalamic
  neurosecretory cells to posterior pituitary for
  storage
• Released into blood in response to nerve impulses
  from the hypothalamus

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Posterior Pituitary, Visual
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OH!!! for Oxytocin

• Released in significant amounts only during
  childbirth and in nursing women
• Stimulates powerful contractions of the uterine
  muscles during labor, sexual relations, and when
  female is nursing
• Also causes milk ejection (letdown reflex) in
  nursing women
• Natural/synthetic oxytocic drugs (pitocin) used
  to induce/hasten labor, stop postpartum bleeding,
  and stimulate milk ejection reflex

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Antidiuretic Hormone

• Diuresis is urine production
• Antidiuretic is chemical that inhibits and/or
  prevents urine production
• ADH causes kidneys to reabsorb more water from
  forming urine
• Results in urine volume DECREASE and blood volume
  INCREASE
• In large amounts, ADH increases blood pressure by
  causing constriction of arterioles (small
  arteries)
• ADH sometimes called VASOPRESSIN

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Diabetes Insipidus

• Hyposecretion of ADH leads to condition of
  excessive urine output called diabetes insipidus
• Individuals with this problem are continually
  thirsty and drink large amounts of water

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Thyroid Gland

• Thyroid located at base of throat, inferior to
  Adams apple where easily palpated
• Large gland of two lobes joined by central mass
  called isthmus
• Internally, composed of hollow structures called
  follicles which store sticky colloidal material
• Thyroid iodine-containing hormone derived from
  colloid
• Produces 2 active hormones T3 and T4
• Also produces calcitonin (thyrocalcitonin)

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Thyroid, Visual
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T3 and T4

• Thyroid hormone (bodys major metabolic hormone)
  actually two iodine-containing hormones
• Tetraiodothyronine (thyroxine or T4)
• Triiodothyronine (T3)
• Thyroxine (T4) is major hormone secreted by
  thyroid follicles
• Most T3 formed at target tissues by conversion of
  T4 to T3

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The Ts, cont.

• Both are very similartwo tyrosine amino acids
  linked by either 3 or 4 iodine atoms
• Controls rate at which glucose is converted to
  chemical energy and heat
• EVERY cell in body is target for thyroid hormone
• Also important for normal tissue growth and
  development especially in reproductive and
  nervous systems

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Remember it well

• GOITER is enlargement of thyroid gland
• caused by diet deficient in iodine
• TSH keeps calling for thyroxine and thyroid gland
  continues to enlarge to make more
• Only peptide part of molecule is made but without
  iodine it is NONFUNCTIONAL
• fails to provide negative feedback to inhibit TSH
  release
• Uncommon in US today because of iodized salt

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Cretinism, Myxedema, and more

• Cretinism results in dwarfism where adult body
  proportions remain childlike
• Caused by hyposecretion of throxine in early
  childhood
• Untreated leads to mental retardation, scanty
  hair, and very dry skin
• Discovered early, HR can prevent signs and
  symptoms of deficiency

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C, M, and morecont.

• Myxedema caused by hyposecretion of thryoxine
  during adulthood
• Mental and physical sluggishness, puffiness of
  face, fatigue, poor muscle tone, low body
  temperature, obesity, and dry skin
• Oral thyroxine is prescribed
• HYPERTHYROIDISM usually results from tumor of
  thyroid gland extreme overproduction of
  thyroxine

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C, M, and morecont.

• High metabolic rate, intolerance of heat, rapid
  heart beat, weight loss, nervous and agitated
  behavior, inability to relax
• Graves disease is one form of hyperthyroidism
• May also cause thyroid to enlarge eyes to bulge
  or protrude anteriorly in condition called
  exophthalmos

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Calcitonin

• Calcitonin (thyrocalcitonin) is second major
  hormone of the thyroid gland
• Decreases blood calcium levels by causing calcium
  to be deposited in bone
• Antagonistic to parathyroid hormone
• Made by C cells found in connective tissue
  between follicles
• Released into blood in response to gting levels of
  blood calcium
• Believed calcitonin production is meager or
  absent in elderly
• Calcitonin is hypocalcemic hormone lt calcium in
  blood

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Calcium Homeostasis, Visual
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Parathyroid Glands

• Are tiny masses of glandular tissue found on
  posterior surface of thyroid gland
• Typically 2 on each lobe (8 reported)
• Secrete parathyroid hormone (PTH) or parathormone
• Most important regulator of calcium ion (Ca2)
  in blood
• Calcium levels drop below certain level,
  parathyroids release PTH which stimulates bone
  destruction cells (osteoclasts)

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Parathyroids, cont.

• Osteoclasts break down bone matrix and increase
  blood levels of calcium
• PTH is hypercalcemic hormone because it acts to
  gt blood levels of calcium
• Another example of negative feedback
• PTH also stimulates kidneys and intestine to
  absorb MORE calcium from forming urine and
  foodstuff

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Hypo versus Hypercalcemia

• Hypocalcemia can be caused by hypoparathyroidism
  (poor diet, lack of vitamin D, and/or renal
  failure)
• Blood calcium levels drop too low, neurons become
  extremely irritable/overactive
• Neurons deliver impulses to muscles at such rapid
  rate that muscles go into uncontrollable spasms
  (tetany)
• Convulsions, intestinal cramps, weak heartbeat,
  cardiac arrhythmias, osteoporosis (what a lesson)

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Hypo/Hyper, cont.

• Hypercalcemia results when calcium blood levels
  become too high
• Can be caused by hyperparathyroidism (cancer,
  vitamin D toxicity, calcium supplement overdose)
• Confusion, muscle pain, cardiac arrhythmias,
  kidney stones, fatigue, and calcification of soft
  tissue
• Is it catching????

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Adrenal Glands

• Adrenal glands curve over top of kidneys
• Each is structurally/functionally two endocrine
  glands
• Like pituitary, the adrenal has glandular
  (cortex) and neural (medulla) parts
• Central medulla enclosed by adrenal cortex which
  contains three separate layers of cells
• Adrenal cortex produces 3 major groups of STEROID
  hormones called corticosteroids

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Adrenal Glands, cont.

• Mineralocorticoids, Glucocorticoids, and sex
  hormones
• Mineralocorticoids, mainly aldosterone, produced
  by outermost adrenal cortex layer
• Important in regulating mineral (salt) content of
  bloodespecially of sodium and potassium ions
• Their target is kidney tubules that selectively
  reabsorb minerals or allow them to be flushed out
  in urine

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Adrenal glands, cont.

• Blood levels of aldosterone gt, kidney tubule
  cells reclaim gting amounts of sodium ions
• Allows more potassium ions to be excreted in
  urine
• When sodium reabsorbed, water follows
• Results in gted blood volume and blood pressure
• Mineralocorticoids help regulate both water and
  electrolyte balance in body fluids

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Aldosterone Release, Visual
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Adrenals and Glucocorticoids

• Cortisone Cortisol are 2 glucocorticoids
  produced by MIDDLE cortex layer
• Promote normal cell matabolism and help body
  resist long-term stressors primarily by gting
  blood glucose levels
• High levels of glucocorticoids in blood prompt
  body cells to convert fats and proteins to
  glucose
• Glucocorticoids are hyperglycemic hormones

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Glucocorticoids cont.

• Help control inflammation by lting edema
• Reduce pain by inhibiting pain-causing molecules
  called prostaglandins
• Often prescribed for patients with rheumatoid
  arthritis to suppress inflammation
• Glucocorticoids released from adrenal cortex in
  response to rising blood levels of ACTH

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Adrenals and Sex hormones

• Regardless of gender, adrenal cortex produces
  small amounts of both male and female sex
  hormones throughout life
• Innermost layer of adrenal cortex produces the
  bulk of the adrenal-produced sex hormones
• Androgens (male hormones) and some estrogen also
  produced

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Addisons Disease

• Addisons disease caused by hyposecretion of
  adrenal cortex hormones
• Major sign is peculiar bronze skin tone
• Aldosterone levels lt sodium water lost from
  body problems with electrolytes and water
  balance
• causes muscles to become weak/shock possible
• Low levels of glucocorticoids results in
  hypoglycemia lessened ability to cope with
  stress (burnout) and suppression of immune system
  increased susceptibility to infection
• Complete lack of glucocorticoidsauf wiedersehen

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Cushings Syndrome

• Hypersecretion usually result of tumor
• If tumor in middle cortex region, Cushings
  syndrome occurs
• Excessive output of glucocorticoids results in
  moon face and appearance of buffalo hump of
  fat on upper back
• Also high BP, hyperglycemia, and possible
  diabetes, weakening of bones, and severe
  depression of the immune system

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Trying things on

• Tumor in zona reticularis of cortex layer can
  cause excessive production of either androgens or
  estrogen
• If androgen gts dramatically, produces symptoms of
  adrenogenital syndrome
• In womengradual development of male secondary
  sexual characteristics (body and facial hair,
  adipose tissue distribution, and muscular
  development)
• In estrogen gts, leads to gynecomastia
• Male develops female secondary sexual
  characteristics

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ANS and Adrenal Medulla

• Adrenal medulla (like posterior pituitary)
  develops from neural tissue
• When stimulated sympathetic NS neurons, its cells
  release 2 similar hormones
• Hormones called catecholamines
• Epinephrine (adrenaline) norepinephrine
  (noradrenaline)
• Sympathetic division called fight or flight
  response division of ANS
• gt heart rate, blood pressure, blood glucose
  levels and dilation of small passageways of lungs
• Body better able to deal with short-term stressor
• Causes the alarm stage of the stress response

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The Pancreas

• Pancreas located close to stomach in abdominal
  cavity and is MIXED gland (both endocrine
  exocrine)
• Tiny masses of hormone-producing cells scattered
  among enzyme-producing cells
• pancreatic islets (islets of Langerhans)
• Islet cells produce insulin glucagon
• Both help regulate sugar (glucose) in blood but
  in opposite ways
• Beta cells produce insulin and Alpha cells
  produce glucagon

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Pancreas, Visual
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Release and Function of Insulin

• High blood levels of glucose stimulate beta cells
  to produce insulin
• Insulin acts on ALL body cells and gts their
  ability to transport glucose across their PMs
• Once inside, glucose used for energy or converted
  to glycogen or fat for storage
• Insulin sweeps glucose from bloodhypoglycemic
• Blood glucose levels fall?insulin release ends
  (classic negative feedback)

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Insulin, cont.

• Insulin is ONLY hormone that lts blood glucose
  levels
• It is absolutely necessary for use of glucose by
  body cells
• Glucagon, glucocorticoids, and epinephrine
  increase blood glucose levels and are
  hyperglycemic

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Blood Glucose Regulation
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Diabetes Millitus

• Condition in which blood glucose levels rise to
  600 mg/100 ml compared to normal of 80-100 mg/100
  ml because of lack of insulin
• Kidney tubules cannot absorb glucose fast enough
  so spills into urine
• As glucose flushes from body, water follows
  leading to dehydration
• Cells cannot use glucose so fats/proteins broken
  down for energydecline in body weight
• Loss of body proteinsdecreased ability to fight
  infections

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Diabetes Millitus, cont.

• Use of large amts. of fat for energy results in
  ketones in bloodacidosis as blood becomes more
  acidic
• Unless correcteddeath
• 3 cardinal signs of diabetes milliuts
• Polyuria (excessive urination)
• Polydipsia (excessive thrist)
• Polyphagia (hunger)
• Mild cases (Type II/adult onset) treated with
  special diets/oral meds to stimulate islets
• Type I (juvenile/brittle) requires insulin
  injections

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Glucagon Function/Release

• Glucagon released by alpha cells of islets
• Release stimulated by LOW blood levels of glucose
• Action is basically hyperglycemic
• Primary target organ is liver where stimulates
  breakdown of glycogen to glucose and its release
  into the blood

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Pineal Gland/Body

• Small, cone-like gland found in roof of 3rd
  ventricle of brain
• Secretes melatonin gts at night lts during day
• Plays role in bodys day and night cycle
• May be related to mating behavior and
  coordination of hormones of fertility
• Inhibits sexual maturation occurrence during
  childhood

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Thymus Gland

• Located upper thorax, posterior to sternum
• Large in infants, decreases in size during
  adulthoodby old age just fibrous connective
  tissue and fat
• Produces thymosin which programs T cells
• In childhood, is incubator for maturation of T
  lymphocytes (WBCs important in immunity)

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Ovaries

• Paired, almond shaped organs located in pelvic
  cavity
• Produce estrogens and progesterone
• Estrogens (estrone estradiol) produced by
  Graafian follicles of ovary stimulate
  development of secondary sexual characteristics
• Work with progesterone to prepare uterus to
  receive fertilized egg
• results in cyclic changes menstrual cycle

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Ovaries, cont.

• Estrogens help maintain pregnancy and prepare
  breasts for lactation
• placenta source at this time and not ovaries
• Progesterone (with estrogen) bring about
  menstrual cycles
• During pregnancy, quiets muscles of uterus to
  prevent abortion
• Also assists in preparing breasts for lactation

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Ovaries, cont.

• Progesterone also secreted by corpus luteum
• CL produces estrogen/progesterone in gting amounts
• Ovaries stimulated to release estrogen and
  progesterone in cyclic way by anterior pituitary
  gonadotropic hormones of FSH and LH

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Testes

• Testes produce male sex hormones (androgens) of
  which testosterone is most important
• Testosterone produced by interstitial cells of
  testes and causes development of adult male sex
  characteristics
• Promotes growth/maturation of reproductive system
• Promotes development of SSCs such as growth of
  beard, development of heavy bones/muscles,
  lowering of voice
• Stimulates male sex drive

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Testes, cont.

• Testosterone necessary for continuous sperm
  production during adulthood
• Production is stimulated by LH from anterior
  pituitary gland
• Its the testosterone that killing us, guys, but
  what a Catch 22!!!

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Placenta

• Formed temporarily in uterus of pregnant woman
• Has role in respiratory, excretory, and nutrition
  delivery system for fetus
• Also produces hormones that help maintain
  pregnancy
• Human chorionic gonadotropin (hCG) produced by
  conceptus and then by fetal part of placenta
• Found only in urine of pregnant women/is basic
  for EPTs (monoclonal antibody technology)

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Placenta, cont.

• hCG stimulates corpus luteum to continue
  producing estrogen/progesterone so uterine lining
  NOT sloughed off
• In 3rd month, placenta assumes job of production
  and ovaries become inactive
• Human placental lactogen (hPL) works with
  estrogen/progesterone to prepare breasts for
  lactation
• Relaxin causes mothers pelvic ligaments pubic
  symphysis to relax and become more flexible
• Eases birth passage

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Old dogs/children/WM wine

• Endocrine system seems to work smoothly until old
  age
• Late middle age menopause for women
• Estrogen deficiency can lead to arteriosclerois,
  osteoporosis, decreased skin elasticity, changes
  in operation of sympathetic nervous system,
  fatigue, nervousness, and mood changes
• For most part, men produce testosterone
  throughout life

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Watermelon wine, cont.

• Efficiency of endocrine system gradually declines
  in old age
• Target organs become less productive
• GH declines muscle atrophy
• Most older people hypothyroid
• Pineal gland calcifies and immune system becomes
  compromised
• Decline in insulin production occurs and
  adult-onset diabetes common in elderly