1. CHAPTER 18 The Endocrine System

2. Cellular Communication
Direct communication between cells via gap junctions = allows molecules, nutrients, electrolytes to move cell to cell.
Synaptic - Nervous - Sensory system- Fast - Transmits impulses - within seconds. Chemicals neurotransmitters from neurons travel across synaptic cleft
Endocrine - comprised of glands, tissues, and cells that secrete hormones (chemical messengers) that diffuse into blood and travel to specific target cells or organs (Ex: insulin) Regulates long-term processes - chemical system- slower - Affect last days, hours or months; often at a distance
Classical Hormones: secreted from endocrine cells directly into interstitial fluid; diffuse into blood; distributed to the body
Neurohormones: synthesized in neuroendocrine cells and secreted from nerve terminals; Transported by blood vessels
Local Hormones: secreted into the interstitial fluid and act locally, on neighboring cells
Paracrine (“para”-close by/LOCAL) extracellular fluid hormones/regulators act on neighboring cells; Most common form of intercellular communication Ex: clotting factors,
Autocrines: Local regulators released by body cells to act on the same cells Ex: Interleukin-2
Endocrinology study of the diagnosis and treatment of its disorders
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3. Communication by the Nervous and Endocrine Systems
Exocrine glands - Secrete substances directly onto the surface or through a tube/duct
Secrete enzymes, mucus, water, oils or other fluids
Examples: Goblet cells, sebaceous gland, sudoriferous
Endocrine glands - Secrete chemicals that diffuse into blood -ductless glands
Secrete hormones
Examples: Pituitary gland, thyroid gland, adrenal gland, pancreas

5. http://classes. midlandstech. edu/carterp/Courses/bio211/chap16/chap16
HUMORAL condition or a chemical OTHER THAN a hormone stimulates endocrine gland. Ex: decreased blood Ca2+ levels stimulates parathyroid gland to secrete PTH
NERVE impulse Ex: sympathetic nerve stimulation stimulates adrenal cortex to release epinephrine and NE that increase blood sugar, heart rate, breathing  help the body cope with stress
HORMONAL- a hormone stimulates the secretion of another hormone. This is a “TROPIC” hormone Ex: Hypothalamus secretes thyrotropin releasing hormone (TRH*)  TRH stimulates anterior pituitary to secrete thyroid stimulating hormone (TSH)

6. Characteristics and Functions
Endocrine glands can produce one or more types of hormones. Over 50 known hormone types
Specific target cells or organs have individual RECEPTOR proteins on their membranes or within the cell that recognize / respond to each hormone.
Hormones can have one or more types of TARGET cells.
Ex: NE increase can target heart cells and respiratory cells.
Hormones MEASURED via blood or urine samples
Functions:
Maintenance of homeostasis (water, pH, blood, blood sugar, temperature, minerals)
Regulation of metabolism
Regulation of growth, development and reproduction
NEW = Stimulates synthesis of an enzyme or structural protein NOT already present in the cell
CURRENT = Alters the presence/synthesis of a particular enzyme or protein by increasing or decreasing the rate of transcription or translation in nucleus & cytoplasm of the cell.
CHANGES ACTIVITY = Turns an existing enzyme or protein CHANNEL on or off by changing its shape or structure

7. Target and Receptor Regulation
Activation of a hormone dependent on:
The concentration of hormones in the blood
Number (#) of RECEPTORS on the target cell
up-regulation Absence of a hormone triggers INCREASE in # of HORMONE RECEPTORS
Hormone level low = cells MORE sensitive
down-regulation Presence of a hormone triggers DECREASE in number of HORMONE RECEPTORS
Hormone levels high = cells LESS sensitive
Strength of the BOND between receptor and hormone

8. Hormone Transport in the Blood
Free Hormones
not bound to proteins in the blood; defined as 'active' and easily bind to target cells. Circulate freely for a short period of time, minutes to less than one hour. Taken as shots/injections. Ex: insulin, GH
Water Soluble Hormones
freely transported in the blood; must bind to a membrane receptor to diffuse through the lipid bilayer. Usually CANNOT be taken orally
Lipid Soluble Hormones
require a binding protein to be transported within the blood; freely diffuse through the target cell membranes to initiate a response.
Hormone Binding Proteins
Enable hormones to remain in circulation longer - hormones bound to a protein does not diffuse into the glomerulus of the kidney, preventing excretion in the urine.
Transporters of primarily lipid soluble hormones. Can be specific to a particular hormone, or non specific, having the ability to carry many types of hormone.
Specific Binding Proteins: Cortisol Binding Protein; Thyroid Binding Globulin
Non Specific: Albumin (carries all types of steroids: testosterone)

9. Molecular Classification of Hormones
AMINO ACIDS – Protein based- Mostly water soluble, lipid insoluble
Amino acid derivatives: Small protein molecules (aka biogenic amines);; formed from two specific amino acids
tyrosine - epinephrine, norepinephrine, dopamine, thyroid
tryptophan - melatonin
Peptide hormones- Large protein molecules -INACTIVE until secreted
glycoproteins, = TSH, LH, FSH
short polypeptides/ small proteins = GH and PRL, ADH, OXT
ANP(heart), thymus (thymosin); digestive tract (gastrin, CCK, secretin)
LIPID DERIVATIVES derived from cholesterol
Steroid hormones:Derived from cholesterol (4 rings of carbon) Water insoluble, lipid soluble EX: estrogens, progesterone, testosterone, cortisol, DHEA, corticosterone, aldosterone (adrenal gland), and calcitriol (kidney)
Eicosanoids: (i-ko-sa-noyds) Signaling molecules coordinate cellular activities and affect enzymatic processes (such as blood clotting, inflammation)
Derived from oxidation of omega 3 & 6 fatty acids; that make up cell membrane and nuclear membrane.
Eicosanoids are not stored within cells, but are synthesized as required. Local regulators (Paracrines)
EX: Prostaglandins from membranes of damaged cell

10. GASEOUS LOCAL REGULATORS
Nitric oxide (NO) secreted by endothelial cells lining blood vessels  acts on smooth muscle fibers in the wall of the blood vessels  causes vasodilation of the blood vessels
Ex: erection of the penis (Viagra)
The immune system produces nitric oxide in order to kill invading bacteria
Also acts as a neurotransmitter between nerve cells

11. Hormone Administration Mechanisms
Two (2) basic mechanisms of hormone action:
LIPID (FAT) SOLUBLE HORMONES Ex: – testosterone, cortisol
Utilizes a “FIRST MESSENGER” -- Mostly steroid hormones
NOT broken down by digestive enzymes; Can be taken orally
Must be bound to transport proteins in plasma
Hormone moves from blood capillary diffuses through the phospholipid bilayer of the target cell’s plasma membrane either binds to the specific cytoplasmic receptor WITHIN the cell OR diffuses through the NUCLEAR (nucleus) membrane to bind to nuclear receptor for activation of specific areas on DNA to produce new proteins
These proteins could be enzymes or transport proteins needed for specific hormone action
EX: Testosterone stimulates synthesis of enzymes & structural proteins in muscle fibers-increasing muscle size and growth

12. Hormone Administration Mechanisms
Water soluble hormones Requires BOTH 1st and 2nd Messengers
Mostly amine, peptide, protein hormones
Usually broken down by powerful gastric digestive enzymes
Taken as shots/injections – Ex: insulin, growth hormone
Circulate freely in plasma
First Messenger - HORMONE
Hormone diffuses from blood; binds to receptors on outer surface of target cell plasma membrane- this transmits chemical message to interior of the cell. Water soluble protein based hormone are unable to pass through the phospholipid bilayer of the plasma membrane.
EXCEPTION: For some years it was believed thyroid hormone, though protein based, could navigate the phospholipid bilayer as its hormone receptors were present INSIDE (intracellular) the cell not on the exterior membrane. However, current research has now confirmed that thyroid hormone does NOT passively cross the membrane but requires a transport channel

13. Hormone
2nd messenger I

15. Hormone Administration Mechanisms
Second Messengers relay signals from receptors on the cell surface to target molecules INSIDE THE CELL
Activated when hormone binds to receptor on cell membrane.
Hormone binds to receptor this activates G proteins
G protein activates adenylate cyclase which converts ATP to cyclic-AMP (cAMP) within cell; cAMP acts as 2nd messenger
G protein can also trigger opening of Ca ion channels in membrane; Ca acts as 2nd messenger to activate enzymes to stimulate hormones: E, NE, OXT
APPROXIMATELY 80% OF PRESCRIPTION DRUGS TARGET RECEPTORS COUPLED TO G PROTEINS
Cyclic-AMP (cAMP)
opens ion channels
activates cytoplasm enzymes; Ex: enzyme that breaks down glycogen stores in skeletal muscles
activates protein kinases that produce phosphorylation which synthesizes ATP used to activate some enzymes; deactivates others.
Phosphodiesterase ( PDE) breaks down cAMP.

16. Hormones
AMPLIFICATION: Small # of hormones bound to plasma receptors can result in 1000s of SAME TYPE 2ND MESSENGERS (Ex: cAMP)
RECEPTOR CASCADE - One hormone may stimulate the release of MORE THAN ONE TYPE of 2nd messenger (cAMP, cGMP, etc)
Most body functions regulated by 2 or more hormones interacting
Permissive interaction one hormone is required before the target cell can respond to another hormone. Ex: Estrogen and progesterone necessary to develop and maintain uterine lining during pregnancy.
Synergistic interaction two or more hormones complement each other to produce a greater response. Ex: FSH or testosterone work together to insure adequate synthesis of sperm
Antagonistic interaction two hormones oppose action of the other Ex: Insulin decreases blood sugar; glucagon increases blood sugar;
Stimulate Negative feedback control – MOST COMMON
OPPOSITE AFFECT Ex: blood Ca2+ low parathyroid hormone (PTH) increases bone deterioration and release of calcium from bone
Positive feedback control – NOT AS COMMON
SAME AFFECT hormone continues the reaction

17. Endocrine glands Some endocrine glands secrete hormone as their
primary function:
Thyroid gland
Parathyroid
Adrenal gland
Pineal gland
Pituitary gland
Other endocrine glands
secrete hormones as their
secondary function:
Thymus
Pancreas
Ovaries
Testis
Hypothalamus
Stomach
Kidneys
Small intestine
Endocrine glands

18. Hypothalamus
(hypo=under)
LINKS NERVOUS SYSTEM WITH ENDOCRINE SYSTEM Connected to pituitary gland by infundibulum
Releases hormones to the anterior pituitary- ENDOCRINE tissue moves via CAPILLARIES from the hypothalamus- Makes specific releasing and inhibitory tropic hormones that stimulate the anterior pituitary
Releases hormones to the posterior pituitary: NERVOUS tissue
Does not make hormones
NEUROSECRETORY cells of the hypothalamus make the hormones  the axons of these cells go through the infundibulum  axon terminals located in the posterior pituitary  hormones are stored and released when stimulated by a NERVE impulse
Pituitary Gland enlarges by 50% during pregnancy

20. Hypothalamic Hormones
eight hormones. 1 factor produced in hypothalamus
seven (7) releasing and inhibiting hormones/factors stimulate () or inhibit the anterior pituitary
Thyrotropin Releasing Hormone (TRH  TSH)
Corticotropin Releasing Hormone (CRH)  ACTH)
Gonadotropin Releasing Hormone(GnRH)  FSH. LH)
Prolactin Releasing Factors (PRF  PRL)
Prolactin Inhibiting Hormone (PIH) [dopamine] inhibits secretion of prolactin
Growth Hormone Releasing Hormone (GHRH  GH)
Somatostatin (GHIH) inhibits secretion growth hormone & thyroid stimulating hormone (TSH) by the anterior pituitary
Two hormones (2) are released into capillaries in the posterior pituitary when hypothalamic neurons are stimulated
oxytocin (OT)
antidiuretic hormone (ADH)
TROPIC HORMONE - A hormone that stimulates another endocrine gland to make its hormones

21. Hypothalamus
Pituitary Gland

23. Anterior Pituitary (*Adenohypophysis) Hypothalamo Hypophyseal Portal System
Portal system contains blood vessels linking 2 capillary networks.
1) Internal carotid artery branches into
2) Superior hypophyseal artery that forms
3) PRIMARY plexus capillaries. Primary plexus capillaries form hypothalamo hypophyseal portal system enters through the infundibulum. Hormones enter primary plexus from hypothalamus through the infundibulum.
Blood drains from capillaries into the
4) hypophyseal portal veins which splits into the
5) SECONDARY plexus capillaries inside the anterior pituitary
Anterior pituitary is stimulated or inhibited to release its hormones
6) Anterior Hypophyeal vein picks up hormones secreted by anterior pituitary and circulated throughout the body.
*Adeno=gland

24. Portal System 1 2 3 4 5 6 Picks up hormones from hypothalamus
Internal carotid artery 1 2 3 4 5 6

25. Releasing / Inhibiting Hormones Kidneys, Uterus and mammary
HYPOTHALMUS
Releasing / Inhibiting Hormones
TRH, CRH, PIH (dopamine), PRF, GnRH, GHRH, GHIH (somatostatin), ADH, OT
ADENOHYPOPHYSIS
Anterior
TSH, ACTH, GH, FSH, LH, PRL
Glands and Tissues
Thyroid, Adrenal cortex, Gonads, Mammary, Liver, Bone, muscles, cartilage
NEUROHYPOPHYSIS
Posterior
Stored: ADH, OT
Glands, Organs, Tissues
Kidneys, Uterus and mammary

26. Anterior Pituitary Hormones
Anterior lobe of the pituitary synthesizes and secretes six (6) principal hormones
GH (growth hormone)
stimulates mitosis and cellular differentiation; increases glycogen breakdown in the liver- elevates blood glucose
TSH (thyroid stimulating hormone)
stimulates secretion of thyroid hormone
Two gonadotropin hormones that target gonads
FSH (follicle stimulating hormone)
stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production
LH (luteinizing hormone)
stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterone
PRL (prolactin)
after birth stimulates mammary glands to synthesize milk, enhances secretion of testosterone by testes
ACTH (adrenocorticotropic hormone)
stimulates adrenal cortex to secrete glucocorticoids- cortisol

27. Anterior Pituitary Hormones
Human Growth Hormone (hGH) - Most active in early childhood years; secretion decreases during puberty - Pituitary secretes 1000x more GH than any other hormone
Stimulates Growth/size and division of body cells (skeletal, cartilage and muscle cells) by promoting the uptake of amino acids
Accelerates protein & ATP synthesis, fat metabolism, blood sugar level
Regulation - Decreased blood sugar (hypoglycemia)  stimulates hypothalamus to release GHRH  stimulates anterior pituitary  increased hGH secretion  releases glucose from liver glycogen storage - Increased blood sugar (hyperglycemia)  stimulates GHIH secretion by hypothalamus  inhibits anterior pituitary  decreased hGH
HYPERSECRETION of growth hormone (GH)
gigantism in childhood or adolescence
treated with somatostatin - GHIH
Diabetogenic effect : symptoms similar to diabetes mellitus (increased blood sugar) Promotes excessive release of stored glycogen from liver.

28. Anterior Pituitary Disorders Continued
HYPERSECRETION of growth hormone (GH)
ACROMEGALY - in adults: thickening of bones and soft tissues especially hands, feet and face. Often associated with gigantism
Usually (90%) result of benign noncancerous tumor in the pituitary
Effects of non-permanent development (high blood pressure, diabetes, headaches, vision issues, muscle weakness)
Can be reversed with the reduction of GH
HYPOSECRETION
DWARFISM – rare - GH now made by genetically engineered bacteria
Age 52
Age 9
Age 16
Age 33
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29. Anterior: Thyroid Stimulating Hormone (TSH)
TROPIC HORMONE
Stimulates: Thyroid gland  increased secretion of thyroid hormones, T3 and T4  increased metabolism
Can cause metabolic disorders
Regulation:
Decreased metabolism stimulates Thyrotropin Releasing Hormone (TRH) by hypothalamus  increased TSH by anterior pituitary - Result: Increased metabolism
Decreased TRH secretion by hypothalamus  decreased TSH secretion by anterior pituitary.
Result: Decreased metabolism

30. Anterior Adrenocorticotropic Hormone (ACTH)
TROPIC HORMONE that stimulates the cortex of the adrenal gland to secrete CORTISOL = HYDROCORTISONE
Stimulation of cortisol no other adrenal hormones.
Primary Function: suppress the immune system by reducing inflammation
Primary function is to increases blood sugar through gluconeogenesis (metabolic pathway that results in the generation of glucose from non-carbohydrate substance such as protein)
released in response to stress (fever, hypoglycemia, etc)
aids in fat, protein and carbohydrate metabolism.
decreases bone formation
Prolonged elevated levels can lead to muscle wasting
Regulation: Increased stress, inflammation - Corticotropin Releasing Hormone (CRH) secretion by hypothalamus  increased ACTH secretion by anterior pituitary  increased cortisol secretion by adrenal cortex

31. Anterior Gonadotropins
Follicle Stimulating Hormone (FSH) OVARIES TROPIC HORMONE stimulates FOLLICULAR DEVELOPMENT; produces OVUM-EGG
- INCREASES female hormone secretions (estrogen, progesterone)
TESTES - stimulate SPERM formation
Luteinizing Hormone (LH)
OVARIES - stimulates OVULATION and release of egg; follicle becomes corpus luteum that secrete progesterone at pregnancy
TESTES -TROPIC HORMONE increased secretion of MALE HORMONES (testosterone, inhibin)
Regulation:
Decreased sex hormones  increased (GnRH) by hypothalamus  increased FSH and LH secretion  increased sex hormones by ovaries and testis
Increased sex hormones  decreased (GnRH) secretion by hypothalamus  decreased FSH and LH  decreased hormones
Clinical application: reproductive disorders due to their affect on secretion of sex hormones

32. Anterior Prolactin (PRL) Stimulates:
In females - mammary gland; MILK PRODUCTION
In males causes testes to be MORE SENSITIVE TO LH which increases and enhances the secretion of TESTOSTERONE.
Regulation:
Decreased estrogen INCREASES Prolactin RELEASING Factor (PRF) secretion by hypothalamus in preparation for potential pregnancy  increased prolactin causes tenderness of mammary gland (breast soreness)
Increased estrogen INCREASES Prolactin INHIBITING Hormone (PIH - dopamine) secretion by hypothalamus decreased Prolactin secretion by anterior pituitary
Infant suckling after delivery  increased PRF and decreased PIH secretion by hypothalamus  increased prolactin secretion by anterior pituitary  increased milk production in mammary gland

33. POSTERIOR PITUITARY (Neurohypophysis) Hormones
Hypothalamus neurosecretory cells produce two hormones (ADH and OT)
transported through axons that form the hypothalamic hypophyseal TRACT (neuron axon) passes through the infundibulum
Released by nerve impulse from hypothalamus (supraoptic and paraventricular nuclei-cell body) to the axon terminals
Hormones stored in the axon terminals in posterior pituitary
Hormones are released into capillaries formed by inferior hypophyseal artery (remember the superior hypophyseal artery branched into the hypophyseal portal system); then circulate throughout the body.

34. Posterior Oxytocin (OT) Secretions- Stimulated by nerve impulses
Promotes emotional bonding mother to infant
STIMULATES:
Smooth muscle contraction in the wall of the uterus  delivery of the baby
Positive feedback system - Low OT during delivery  Pitocin (commercial form of OT) shot is given to induce labor
Smooth muscle contraction in mammary duct releases milk
Regulation of milk release - Infant suckles  nerve impulses are generated  impulses reach hypothalamus  stimulates release of OT from axon terminals located in posterior pituitary  smooth muscle contraction in mammary gland and uterus  milk release and toning of uterus
Posterior

35. Posterior Antidiuretic Hormone (ADH)
Vasopressin stimulated by water levels in blood
Stimulates: H2O reabsorption at distal convoluted tubule and collecting duct of kidney units
Regulation:
Low water intake  hypothalamus detects osmolarity of blood  neurosecretory cells in hypothalamus generate impulses  stimulates release of ADH from axon terminals located in posterior pituitary  ADH stimulates water reabsorption in kidneys  less urine formed  water is conserved
High water intake  hypothalamus detects osmolarity of blood  neurosecretory cells in hypothalamus do not generate impulses  less ADH released from axon terminals located in posterior pituitary  less water reabsorption in kidneys  more urine formed
Clinical application:
Diabetes insipidus: HYPOSECRETION of ADH  symptoms similar to diabetes mellitus (large amounts of urine formed and released, resulting in dehydration, thirst).

37. Thyroid Gland Located anterior to trachea and inferior to larynx
follicle cavity
Located anterior to trachea and inferior to larynx
Made of two lobes connected by isthmus; consists sacs called follicles. Follicles store large amounts of hormones
Follicle cells surround a follicle cavity and SYNTHESIZE viscous colloid (a substance microscopically dispersed throughout another substance) called thyroglobulin (globular protein). Thyroglobulin contains the amino acid TYROSINE.
Secretes: Thyroid hormones - T3 and T4 for maintaining metabolism Calcitonin (CT) for maintaining blood calcium level

38. Thyroglobulin made by follicular cells and released into cavity
Iodine moves from the blood thru the follicular cells into the colloid where it binds to TYROSINE in the thyroglobulin. Once iodine is bound, thyroglobulin moves from the follicle cavity back into the follicle cell where T3 and T4 is released (via enzymes) from the thyroglobulin and diffuses from basement membrane of the cell into the blood.
70% of T3 and T4 binds to thyroxine – binding protein allowing it to remain functional and active for a longer period of time than free circulating hormones.
Unlike other protein based hormones, T3/T4 receptors are INSIDE the cell. They have special transporters that move them across the cell membrane.

39. Thyroid Hormones
Tyrosine in thyroglobulin binds with iodine to form the two predominant thyroid hormones
T3 – Triiodothyroxine: tyrosine w/ 3 iodines; effects are 4x more potent than T4; accounts for 20% of hormone in the blood- short half-life
T4 – Thyroxine: tyrosine w/ 4 iodines; used to synthesize T3; accounts for 80% of hormone in blood; longer half-life T4 T3
REGULATION:
THINK
Major factor controlling rate of thyroid hormone release
is the concentration of TSH in the circulating blood!
Metabolic rate  stimulates TRH or TIH release from hypothalamus  regulates release of TSH from anterior pituitary  increased or decreased release of T3 and T4 from follicular cells in thyroids

40. The Thyroid Gland Effects of Thyroid Hormones on Peripheral Tissues
Essential to proper DEVELOPMENT AND DIFFERENTIATION of all cells of the human body
Regulates PROTEIN, CARBOHYDRATE, AND LIPID metabolism affecting how human cells use energetic (food) compounds.
Elevates rates of oxygen consumption and energy consumption; in children, may cause a rise in body temperature (calorigenic effect)
Maintains normal sensitivity of RESPIRATORY CENTERS to changes in oxygen and carbon dioxide concentrations
Stimulates RED BLOOD CELL FORMATION and thus enhances oxygen delivery
Increases HEART rate and force of contraction; generally results in a rise in blood pressure
Accelerates turnover of minerals in BONE
GI TRACT movement

41. Clinical Disorders HYPOTHYROIDISM – too little Goiter
Cretinism: condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones due to maternal nutritional deficiency of iodine.
Myxedema: severe adult hypothyroidism; skin becomes dry and puffy due to accumulation of mucus under the skin. Facial elasticity is compromised. Recovery may be complete if thyroid hormones is given SOON after symptoms appear.
HYPERTHYROIDISM – too much causes muscle weakness, sleeping problems, fast heartbeat. heat intolerance. and weight loss
Graves disease:- autoimmune; caused by thyroid hypersecretion
30-50% of people will also suffer from Graves' ophthalmopathy (a protrusion of one or both eyes).
Fibroblasts in eye muscles differentiate into fat cells (adipocytes).
Fat cells and muscles expand, become inflamed. Veins are compressed, and unable to drain fluid, causing edema.
Treatments can help to lesser the effects; mild cases may be reversed. 1) Radioactive therapy: kills overactive thyroid cells ) Anti-thyroid medications 3) thyroid surgery
Goiter

42. Thyroid Gland Disorders
Graves disease
HYPERTHYROIDISM
Cretinism
HYPOTHYROIDISM
Myxedema
HYPOTHYROIDISM
Before After
Treatment Treatment

43. Endemic Goiter
Follicle cells synthesis colloid but without iodine it cannot produce functioning hormones. Pituitary continues to secrete TSH in an attempt to rectify the inadequate supply of thyroid hormones which results in the accumulation of unusable colloid and swelling. Without treatment, thyroid cells will die and atrophy. 90.5% of goiters result from low iodine.
Treatment to reduce the goiter can be in the form of radioactive iodine (shrinks the thyroid gland), iodine supplementation, or thyroidectomy (surgical removal of all or part of the thyroid gland). Surgery is only necessary in cases where complicated by significant compression of nearby structures

44. Thyroid Hormones Calcitonin (CT)
Made by parafollicular cells (C cells) located between the follicles
Function: Decreases blood calcium
Inhibits osteoclast (which breakdown bone tissue)
Inhibits calcium reabsorption by kidneys
Inhibits absorption of dietary calcium in the intestines
Parathyroid Gland
Four tiny glands on the posterior surface of thyroid gland
PTH Increases blood calcium Decreases bone calcium
Made Chief cells which secrete parathyroid hormone (PTH)

46. Adrenal Gland Located above the kidneys
Consists of: - Capsule - Adrenal cortex – comprised of three zones that secretes 3 types of hormones - Adrenal medulla – secretes 2 types of hormones

47. Adrenal Gland
Capsule – Connective tissue protective layer

48. Adrenal Cortex Hormones
ZONA GLOMERULOSA Glomus “ball”
Mineralocorticoids ALDOSTERONE - Regulate minerals Reabsorption of Na+, Cl-, HCO and H2O; Excretion of K+ and H+
Affects water level in the body
ZONA FASCICULATA Cells organized into fascicles
Glucocorticoids - CORTISOL stimulated by ACTH
Has anti-inflammatory effect; Can compromise immune function
Secreted during a stress response; maintains /redistributes GLUCOSE (energy) to the brain and major muscles during a fight-or- flight situation)
Fetus increases levels to promote SURFACTANT production for lung maturation
Increases protein and lipid breakdown; Increases ATP production
Causes vasoconstriction to INCREASE blood pressure Affects H2O level in the body n

49. Adrenal Gland Disorders
Cushing’s disease: HYPERSECRETION of CORTISOL  redistribution of fat, spindle legs, moon face, pendulous abdomen; usually the result of pituitary tumor
Addison’s disease:
HYPOSECRETION of ALDOSTERONE AND CORTISOL  hypoglycemia, lower BP, dehydration, muscle weakness and fatigue, weight loss, depression
Caused by:
malfunction of the adrenal glands themselves
lack of ACTH.

50. Adrenal Cortex Hormones
ZONA RETICULARIS
Androgens: Secretes some male hormones most synthesized in testis.
main source of testosterone in females
sets libido throughout life
Induces axillary and pubic hair growth during puberty
Clinical application: Hirsutism: hypersecretion of androgens  excessive hair growth
Treatment: Metformin; combination oral contraceptives; waxing, shaving, hair removal

51. Adrenal MEDULLA Hormones
EPINEPHRINE (75-80%)
NOREPINEPHRINE (20-25%)
Similar structure and function - Stimulated when there is an increased need to speed up cellular energy usage
“Fight or flight” response
Response to sympathetic nerve - Increase heart rate, BP, breathing rate , blood sugar, metabolism, and muscle contraction
Increass ENERGY PRODUCTION:
Skeletal muscles, triggers mobilization of glycogen reserves and accelerate the breakdown of glucose to provide ATP
In adipose tissue, stored fats are broken down into fatty acids which are released into the blood ATP production
In the liver, glycogen molecules are broken down and released into blood
Increases in HEART PERFORMANCE
In the heart, triggers an increase in the rate and force of cardiac muscle contraction

52. Pancreas
Located inferiorly and posteriorly to stomach;
Consists of Head, Body and Tail
EXOCRINE (Acini cells) 99% of the tissue – produces digestive enzymes that are released through a pancreatic duct into small intestine
ENDOCRINE 1% of the tissue- Islets of Langerhans/Pancreatic islets – produces hormones that diffuse into blood
Alpha cells - GLUCAGON raises blood glucose levels
Beta cells - INSULIN reduces blood glucose levels
Delta cells- GHIH/somatostatin
inhibits release of insulin and glucagon;
inhibits nutrient digestion and absorption which prolongs absorption of nutrients

53. Primary Pancreas Hormones
INSULIN – removes glucose OUT OF the blood
PROTEIN composed of 51 amino acids. Special transporter proteins in cell membrane allow glucose from the blood to enter a cell;
transporters indirectly under insulin's control
Accelerates glucose utilization and enhances ATP production
Stimulates amino acid absorption and protein synthesis
Promotes the absorption of glucose, fatty acids and amino acids which block the burning of stored body fat in anticipation of new calories
Causes liver and skeletal muscles to store glucose as glycogen
Increases the contents of fat cells (adipocytes) by drawing fatty acids from the blood and storing as triglycerides can lead to obesity
Danger of elevated levels of insulin: high BP, poor Mg storage-inability to relax muscles, cellular proliferation-increase prostate/breast cancer risk
Severe hypoglycemia (LOW blood glucose) or diabetic shock also called insulin reaction, a consequence of too much insulin---causes sudden drop in glucose  can result in coma and death
GLUCAGON – releases glucose INTO the blood (antagonistic)
Stimulates breakdown of glycogen in skeletal muscle and liver cells
Stimulates production of glucose in liver (gluconeogenesis)
Stimulates breakdown of triglycerides in adipose tissue

54. Insulin stimulates the opening of channels/transporters which allow glucose to enter the cell

55. Insulin and Glucagon Regulation
Low blood glucose release of glucagon
High blood glucose secretion of insulin
Somatostatin/GHIH inhibit to regulate insulin and glucagon secretions
Diabetes mellitus
Type I – insulin dependent
childhood diabetes - decrease in beta cells  decrease in insulin secretion results in hyperglycemia
kidneys excrete glucose & large amounts of H2O resulting in dehydration  excessive thirst.
Type II – Non-insulin dependent diabetes - Obese or older adults  fewer insulin receptors on target cells  less response  symptoms as above - Treatment – diet, exercise, Rx, insulin shots

56. Consequences of high glucose levels in blood
Increased susceptibility to bacterial infections; poor injury healing
Increased susceptibility to fungal infections like thrush which thrive on sugar-rich environments.
Nerve damage resulting in constant pain, numbness, tingling burning sensations in the extremities.
Impaired digestion due to loss of nerve functions
Poor blood circulation due to the narrowing of blood vessels causing high BP, heart attack, stroke, gangrene (from the death of tissue due to poor blood circulation) leading to possible amputation of limbs.
Damage to very small blood vessels in the EYES and kidneys leading to blindness and kidney failure.
Ketoacidosis –life threatening condition caused by very high blood sugar levels; associated with fat metabolism and increased acidity. Cells unable to obtain glucose, liver metabolizes fat to provide energy- metabolism produces ketones that increase blood acidity
Accelerated aging - premature aging of tissues visible externally sagging of skin / wrinkles; similar internally tissue integrity damage

57. Blood vessel damage results in leakage.
Presence of blood cells interferes with the ability of photoreceptors to respond to light waves.
Animation;

58. Diabetic ulcer
Foot ulcers are a common complication of diabetes and can lead to amputation.

59. Ovaries and Testis
Primary function: Gamete formation – eggs and sperms
Regulation: Hypothalamus secretes GnRH  anterior pituitary secretes gonadotropins (FSH and LH)  stimulate ovaries (follicular and oocyte development, hormone (estrogen) production) and testis (sperm and hormone (testosterone) production)
Secondary function: Hormone production - Ovaries produce estrogen, progesterone, relaxin, inhibin - Testis produce testosterone, inhibin

60. Pineal Gland Located posterior to thalamus
Has neuroglial cells and secretory cells
Undergoes involution (shrinking of an organ) in adults
Secretes hormone, melatonin
Inhibits reproductive functions - affects secretion of gonadotropins (thought to influence onset of puberty)
Protects against damage by free radicals
Influences circadian rhythm present in the sleeping and feeding patterns, patterns of core body temperature, brain wave activity, hormone production, cell regeneration, other biological activities
Secretion is regulated by light impulses - production of melatonin by the pineal gland is inhibited by light to the retina and permitted by darkness.
Amounts decrease with age

61. Thymus Large organ in infants but atrophied as adult
Large organ in infants but atrophied as adult
2 lobed organ located in mediastinum – superior to the heart
Primary function – maturation of T lymphocytes
Secondary function – secretion of hormone thymosin which aids maturation process

62. Other Endocrine Glands
Stomach: - secretes gastrin to regulate secretion of gastric juices Small intestine: - secretes secretin, cholecystokinin that stimulate pancreas and gall bladder but inhibit stomach Placenta: - secretes several hormones to support pregnancy Liver: - erythropoietin (RBCs), calcidiol (Vitamin D), hepcidin (iron homeostasis), angiotensin (blood vessel constriction, aldosterone release) Kidneys: - secrete erythropoietin (EPO) to stimulate RBC production by red bone marrow