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Chapter 9 The Endocrine System. Biology 112 Tri-County Technical College Pendleton, SC. Hormones are flowing…. Hormones are chemical substances secreted into extracellular fluid that regulate activity of other cells

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Chapter 9 the endocrine system

Chapter 9 The Endocrine System

Biology 112

Tri-County Technical College

Pendleton, SC

Hormones are flowing
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

Hormones cont
Hormones, cont.

  • Reproduction, growth & development, body’s 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

Getting there
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



    • NEURAL

Been there done that
Been there…done 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

Endocrine glands
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)

Pituitary gland
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 “turk’s 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)

Pituitary cont
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)

Growth hormone
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 body’s supply of glucose thereby helping to maintain blood sugar homeostasis

Pituitary abnormalities
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


  • Abbreviated as PRL

  • Protein hormone whose only known target in humans is the breast

  • After childbirth, it stimulates and maintains milk production by mother’s breasts

  • Its function is males is NOT known

Same song different verse
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

Follicle stimulating hormone
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

Luteinizing hormone
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

Pituitary and sterility
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

Anterior pituitary hypothalamus
Anterior Pituitary/Hypothalamus

  • Pituitary used to be called “master gland”

  • Release of pituitary’s 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

Posterior pituitary
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

Oh for oxytocin
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

Antidiuretic hormone
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

Diabetes insipidus
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

Thyroid gland
Thyroid Gland

  • Thyroid located at base of throat, inferior to Adam’s 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)

T3 and t4
T3 and T4

  • Thyroid hormone (body’s 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

The t s cont
The T’s, cont.

  • Both are very similar—two 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

Remember it well
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

Cretinism myxedema and more
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

C m and more cont
C, M, and more…cont.

  • 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

C m and more cont1
C, M, and more…cont.

  • High metabolic rate, intolerance of heat, rapid heart beat, weight loss, nervous and agitated behavior, & inability to relax

  • Grave’s disease is one form of hyperthyroidism

  • May also cause thyroid to enlarge & eyes to bulge or protrude anteriorly in condition called exophthalmos


  • 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 >ing levels of blood calcium

  • Believed calcitonin production is meager or absent in elderly

  • Calcitonin is hypocalcemic hormone; < calcium in blood

Parathyroid glands
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)

Parathyroids cont
Parathyroids, cont.

  • Osteoclasts break down bone matrix and increase blood levels of calcium

  • **PTH is hypercalcemic hormone because it acts to > blood levels of calcium

  • Another example of negative feedback

  • PTH also stimulates kidneys and intestine to absorb MORE calcium from forming urine and foodstuff

Hypo versus hypercalcemia
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)

Hypo hyper cont
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…????

Adrenal glands
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

Adrenal glands cont
Adrenal Glands, cont.

  • Mineralocorticoids, Glucocorticoids, and sex hormones

  • Mineralocorticoids, mainly aldosterone, produced by outermost adrenal cortex layer

  • Important in regulating mineral (salt) content of blood—especially [ ] of sodium and potassium ions

  • Their target is kidney tubules that selectively reabsorb minerals or allow them to be flushed out in urine

Adrenal glands cont1
Adrenal glands, cont.

  • Blood levels of aldosterone >, kidney tubule cells reclaim >ing amounts of sodium ions

    • Allows more potassium ions to be excreted in urine

  • When sodium reabsorbed, water follows

  • Results in >ed blood volume and blood pressure

  • Mineralocorticoids help regulate both water and electrolyte balance in body fluids

Adrenals and glucocorticoids
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 >ing blood glucose levels

  • High levels of glucocorticoids in blood prompt body cells to convert fats and proteins to glucose

  • Glucocorticoids are hyperglycemic hormones

Glucocorticoids cont
Glucocorticoids cont.

  • Help control inflammation by <ing 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

Adrenals and sex hormones
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

Addison s disease
Addison’s Disease

  • Addison’s disease caused by hyposecretion of adrenal cortex hormones

  • Major sign is peculiar bronze skin tone

  • Aldosterone levels <; 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 glucocorticoids=auf wiedersehen

Cushing s syndrome
Cushing’s Syndrome

  • Hypersecretion usually result of tumor

  • If tumor in middle cortex region, Cushing’s 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

Trying things on
Trying things on…

  • Tumor in zona reticularis of cortex layer can cause excessive production of either androgens or estrogen

  • If androgen >s dramatically, produces symptoms of adrenogenital syndrome

  • In women=gradual development of male secondary sexual characteristics (body and facial hair, adipose tissue distribution, and muscular development)

  • In estrogen >s, leads to gynecomastia

  • Male develops female secondary sexual characteristics

Ans and adrenal medulla
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

  • > 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

The pancreas
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

Release and function of insulin
Release and Function of Insulin

  • High blood levels of glucose stimulate beta cells to produce insulin

  • Insulin acts on ALL body cells and >s 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 blood=hypoglycemic

  • Blood glucose levels fallinsulin release ends (classic negative feedback)

Insulin cont
Insulin, cont.

  • Insulin is ONLY hormone that <s 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

Diabetes millitus
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 energy=decline in body weight

  • Loss of body proteins=decreased ability to fight infections

Diabetes millitus cont
Diabetes Millitus, cont.

  • Use of large amts. of fat for energy results in ketones in blood=acidosis as blood becomes more acidic

  • Unless corrected=death

  • 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

Glucagon function release
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

Pineal gland body
Pineal Gland/Body

  • Small, cone-like gland found in roof of 3rd ventricle of brain

  • Secretes melatonin; >s at night; <s during day

  • Plays role in body’s day and night cycle

  • May be related to mating behavior and coordination of hormones of fertility

  • Inhibits sexual maturation occurrence during childhood

Thymus gland
Thymus Gland

  • Located upper thorax, posterior to sternum

  • Large in infants, decreases in size during adulthood—by 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)


  • 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

Ovaries cont
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

Ovaries cont1
Ovaries, cont.

  • Progesterone also secreted by corpus luteum

    • CL produces estrogen/progesterone in >ing amounts

  • Ovaries stimulated to release estrogen and progesterone in cyclic way by anterior pituitary gonadotropic hormones of FSH and LH


  • 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 SSC’s such as growth of beard, development of heavy bones/muscles, lowering of voice

  • Stimulates male sex drive

Testes cont
Testes, cont.

  • Testosterone necessary for continuous sperm production during adulthood

  • Production is stimulated by LH from anterior pituitary gland

  • It’s the testosterone that killing us, guys, but what a Catch 22!!!


  • 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)

Placenta cont
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 mother’s pelvic ligaments & pubic symphysis to relax and become more flexible

    • Eases birth passage

Old dogs children wm wine
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

Watermelon wine cont
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