Endocrine System
LO 2 &3
Chapter 7
Marieb, Elaine N, and Katja. Hoehn. 2019. Human Anatomy and Physiology, Global Edition. 12th
ed. Pearson 0r Higher Ed.
Marieb, Elaine Nicpon, and Simone. Brito. 2018. Anatomy & Physiology Coloring Workbook: A
Complete Study Guide. 12th ed. Pearson
1
Overview
◼ Endocrine system is the body’s 2nd great controlling system
which influences metabolic activities of cells by means of
hormones.
◼ Interact with the body’s 1st great controlling system the…..
Nervous system.
◼ This is achieved through endocrine glands:
1. Pineal
2. Pituitary
3. Thyroid & parathyroid
4. Thymus
5. Adrenals
6. Pancreas
7. Gonads
8. Hormones produced by other organs
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*Hormones
◼ Definition: Chemical substances secreted by cells
into the extracellular fluid and regulate the
metabolic function of other cells.
◼ Cellular response to hormones tend to have a
lag time but once initiated, they have prolonged
effects.
◼ Types of Hormone:
1. Amino acid-based hormones
2. Steroids - (derived from cholesterol)
3. Eicosanoids (i-ko’sa-noyds) - lipid hormones
(from arachidonic acid)
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*Major Endocrine Organs
Figure 16.1
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Endocrine System
Homeostasis
Hyper- Hypo-
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Endocrine Diseases - examples
Thyroid disease:
Hyperthyroidism
Hypothyroidism
Adrenal Gland disease:
Cushing Syndrome
Addison’s Disease
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Mechanism of Hormone Action
◼ Hormones bind to specific receptors on the surface
of a targeted cell
◼ Name comes from a Greek “to arouse”-alter/change
Hormones produce one or more of the following
cellular changes in target cells
1. Change plasma membrane permeability
2. Stimulate protein synthesis
3. Activate or deactivate enzyme systems
4. Promote or inhibit secretory activity
5. Stimulate or inhibit mitosis
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Hormone Concentrations in the Blood
◼ Hormones circulate in the blood in two forms:
1. Bound - Steroid and thyroid hormones are
attached to plasma proteins
2. Free - All others are free
◼ Hormones are removed from the blood by:
1. Degrading enzymes
2. The kidneys
3. Liver enzyme systems
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Control of HormoneRelease
◼ Synthesis and Release of Hormones:
◼ Are controlled by a Negative Feedback System
◼ Because of such system, blood hormone levels vary only within
a narrow range.
◼ Hormones are synthesized and released in response to:
◼ Humoral stimuli - e.g. changes in ion or nutrient levels
◼ Ex: Parathyroid gland monitor blood Ca2+ levels…PTH
◼ Neural stimuli- nerves stimulate hormone release
◼ Ex: Sympathetic nervous system stimulation of Adrenal medulla
….NE & E (adrenalin) during “fight or flight situation”s
◼ Hormonal stimuli- in response to hormones produced by other
endocrine organs. Ex: Anterior Pituitary Hormones regulated by
hormones of the Hypothalamus
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Hormonal Stimuli
HPA
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Nervous System Modulation
◼ The nervous system can modify both the stimulation of
endocrine glands and their negative feedback mechanisms
◼ It does so, to maintain body homeostasis
◼ Example of the nervous system overriding normal
endocrine control
◼Control of blood glucose levels
◼Normally the endocrine system maintains blood
glucose
◼ But when under stress, the body needs more glucose
◼Ample glucose is release because the
Hypothalamus & the Sympathetic nervous system
are activated to supply the needed glucose.
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Hypothalamus Pituitary Axis
Negative – Feedback Loop
*Hormones & their Function
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Pituitary Gland (Hypophysis)
◼ Secretes at least 9 hormones
◼ Two major lobes:
1. Posterior lobe/pituitary
-a neural tissue releasing
neurohormones received from the
hypothalamus
-Neurohypophysis= posterior lobe
+ infundibulum
2. Anterior lobe/pituitary
-a glandular tissue making & releasing
a number of hormones
-Adenohypophysis
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Pituitary-Hypothalamic Relationships:
Posterior Pituitary or Posterior Lobe
◼ The posterior lobe of the pituitary is part of the brain
and is a downgrowth of hypothalamic tissue
◼ There is a neural connection with the hypothalamus via
the hypothalamic-hypophyseal tract.
◼ Nuclei of the hypothalamus synthesize oxytocin and
antidiuretic hormone (ADH), are transported to the
Posterior pituitary.
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Antidiuretic Hormone (ADH) - Vasopresin
◼ ADH helps to avoid dehydration or water overload
◼Prevents urine formation
◼ Alcohol inhibits ADH release and causes copious
urine output (“hangover” dry mouth, intense thirst)
- drinking a lot of water inhibits as well ADH release
◼ Osmoreceptors monitor the solute concentration of the
blood (osmolarity)
◼ With high solutes, ADH is synthesized and released,
thus preserving water
◼ With low solutes, ADH is not released, thus causing
water loss from the body 21
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*Pituitary-Hypothalamic Relationships: Anterior Lobe
◼ The anterior lobe of the
pituitary is an outpocketing of
the oral mucosa
◼ There is no direct neural contact
with the hypothalamus,
but there is a vascular connection-
Hypophyseal Portal System.
◼ *Several releasing hormones are made
in the Hypothalamus and transported to
theAnterior pituitary by way of this
Hypophyseal portal system
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Anterior Pituitary: Adenophypophyseal
Hormones
◼ The six (6) hormones of the adenohypophysis:
◼ Are abbreviated as GH, TSH, ACTH, FSH, LH, and
PRL (prolactin)
◼ Regulate the activity of other endocrine glands
◼ In addition, pro-opiomelanocortin (POMC):
◼ Has been isolated from the pituitary
◼ Is enzymatically split into ACTH, Opiates, and MSH
(melanocyte stimulating hormone)
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*Anterior Pituitary Hormones
◼ Four Anterior Pituitary hormones are tropic
hormones that have regulatory effect on other
endocrine glands.
◼ These Tropic hormones are:
1. Adrenocorticotropic hormone (ACTH)
2. Thyroid-stimulating hormone (TSH)
3. Follicle-stimulating hormone (FSH)
4. Luteinizing hormone (LH)
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Metabolic Action of Growth Hormone
◼ GH stimulates liver, skeletal muscle, bone, and
cartilage to produce insulin-like growth factors
◼ Direct action promotes lipolysis and inhibits
glucose uptake
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Homeostatic Imbalance
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Acromegaly - Gigantism
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*Thyroid gland
◼ This endocrine gland is
capable of storing
thyroid hormone and
then slowly releasing
them.
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Thyroid Hormone
◼ Thyroid hormone – the
body’s major metabolic
hormone
◼ Consists of two closely
related iodine-containing
compounds
◼ T4 (thyroxine)-has two tyrosine
molecules plus four bound
iodine atoms
◼ T3 (triiodothyronine)- has two
tyrosines with three bound
iodine atoms
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Effects of Thyroid Hormone
◼TH is concerned with:
◼Glucose oxidation
◼Increasing metabolic rate
◼Heat production
◼TH plays a role in:
◼Maintaining blood pressure
◼Regulating tissue growth
◼Developing skeletal and nervous systems
◼Maturation and reproductive capabilities
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Thyroid Functions
Regulates basal metabolic rate
Improves cardiac contractility
Increases the gain of catecholamines
Increases bowel motility
Increases speed of muscle contraction
Decreases cholesterol (LDL)
Required for proper fetal neural growth
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Goiter: enlargement of the thyroid
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Goiter
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Graves
Most common cause of hyperthyroidism
Result of anti-TSH receptor antibodies
Patients with Graves’ disease may present with:
Exophthalmos, lid retraction, lid lag (Graves’
ophthalmopathy) which may result in:
blurring of vision, photophobia, increased
tearing, double vision, deep orbital pressure.
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Hyperthyroidism
PHYSICAL FINDINGS & CLINICAL PRESENTATION
Tachycardia, tremor, hyperreflexia, anxiety, panic
attacks, irritability, emotional lability, heat intolerance,
sweating, increased appetite, diarrhea, weight loss,
menstrual dysfunction (oligomenorrhea, amenorrhea);
the presentation may be different in elderly patients.
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Clinical: General Comparison
HYPOTHYROIDISM HYPERTHYROIDISM
Levels of T3 & T4 Low High
TSH
Metabolic Rate Low High
Goiter Present w/ endemic Present w/ Graves’
Skin Pale, cool w/edema Flushed & warm
Temp. tolerance Cool intolerance Heat intolerance
Eyes Exophthalmos
Cardiovascular Bradycardia Tachycardia/ HPN
Nervous system Lethargic Restless, tremors
Body weight Weight increase/ Thin/ increase appetite
decrease appetite
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Adrenal (Suprarenal) Glands
◼Adrenal glands – paired, pyramid-shaped
organs atop the kidneys
◼Structurally and functionally, they are two
glands in one
◼Adrenal medulla – nervous tissue that acts
as part of the SNS
◼Adrenal cortex – glandular tissue
derived from embryonic mesoderm
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Adrenal Cortex
◼ Synthesizes and releases steroid
hormones called corticosteroids
◼ Different corticosteroids are produced in each
of the three layers
◼ Zona glomerulosa –
mineralocorticoids (chiefly
aldosterone)
◼ Zona fasciculata –
glucocorticoids (chiefly cortisol)
◼ Zona reticularis –
gonadocorticoids
(chiefly androgens)
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Adrenal Cortex
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*Mineralocorticoids
◼ Function: Regulate the electrolyte
concentrations of extracellular fluids
◼ *Aldosterone
◼ Accounts for 95% of the mineralocorticoids
◼ Most important regulator of electrolyte concentrations in the
extra cellular fluid
◼ Reduces excretion of Na+ from the body
◼ Aldosterone secretion is stimulated by:
1. Rising blood levels of K+
2. Low blood Na+
3. Decreasing blood volume & pressure
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*Glucocorticoids (Cortisol)
◼ “Influence the energy metabolism of most body cells
and help us resist stressors.”
◼ *Help the body deal with stress by:
◼ Increasing blood glucose levels
◼ Increasing fatty acids and amino acid levels
◼ Enhancing blood pressure
◼ Glucocorticoid secretion is regulated by negative
feedback
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Adrenal Cortex
Overactivity:
Cushing Syndrome:
Excess corticosteroid production or usage
Presentation:
Increased weight (trunk and face), thin limbs,
edema in legs, thin skin, osteoporosis
Underactivity:
Addison’s Disease:
Autoimmune
Presentation:
Weight loss, low blood pressure, anorexia,
nausea, skin hyper-pigmentation, tiredness
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Cushing’s syndrome is the occurrence of clinical
abnormalities associated with glucocorticoid
excess secondary to exaggerated adrenal
cortisol production or long term glucocorticoid
therapy.
Cushing’s disease is Cushing’s syndrome caused
by pituitary ACTH excess
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Cushing Syndrome
(side effect of long-term cortisol)
PHYSICAL FINDINGS & CLINICAL PRESENTATION
Hypertension, hyperglycemia
Central obesity with rounding of the facies (moon
facies); thin extremities
Hirsutism, menstrual irregularities, hypogonadism
Skin fragility, easy bruising, red/purple abdominal
striae/stretch marks, acne, poor wound healing, hair
loss, flushed face, skin hyperpigmentation (when
there is ACTH excess)
Psychosis, emotional lability, paranoia
Muscle wasting with proximal myopathy
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Clinical Application: HYPERCORTISOLISM
(Cushing’s Syndrome)
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Cushing’s Disease
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Clinical: General Comparison
ADDISON’S DISEASE CUSHING’S SYNDROME
Deficit of corticosteroid Excess
corticosteroid
High risk of infection High risk of infection
Poor stress response Poor stress response
Weight loss / fatigue Moon face, buffalo hump,
obese trunk, osteoporosis
Anorexia, nausea, diarrhea Striae, bruising of skin
Hypotension, syncope Hypertension, glucose
intolerance
Hyperpigmentation Fatigue, weakness, delayed
healing
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Adrenal Medulla
◼Made up of chromaffin cells that secrete
epinephrine (E) and norepinephrine (NE)
◼Secretion of these hormones causes:
◼Blood glucose levels to rise
◼Blood vessels to constrict
◼The heart to beat faster
◼Blood to be diverted to the brain, heart, and
skeletal muscle
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Adrenal Medulla: Hormone
◼Epinephrine is the more potent stimulator of
the heart and metabolic activities
◼Norepinephrine is more influential on
peripheral vasoconstriction and blood
pressure
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Stress and the Adrenal Gland
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Figure 16.1 5
•61
Pancreas
◼ A triangular gland, which has both exocrine and
endocrine cells, located behind the stomach
◼ Acinar cells produce an enzyme-rich juice used for
digestion (exocrine product)
◼ Pancreatic islets (islets of Langerhans) produce
hormones (endocrine products)
◼ The islets contain two major cell types:
◼Alpha () cells that produce= glucagon
◼Beta () cells that produce= insulin
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Regulation of Blood GlucoseLevels
◼ The hyperglycemic effects of glucagon and the
hypoglycemic effects of insulin 63
Homeostatic Imbalance: DM
◼ Diabetes mellitus:
Results from hyposecretion or
hypoactivity of insulin
◼ The three cardinal signs of DM
are: 3P’s
◼ Polyuria – huge urine output
◼ Polydipsia – excessive thirst
◼ Polyphagia – excessive
hunger and food
consumption
◼ Hyperinsulinism – excessive
insulin secretion, resulting in
hypoglycemia 64
Diabetes Mellitus (DM)
Figure 65
16.18
Gonads
Female: Ovaries
◼ Paired ovaries in the abdominopelvic cavity produce
estrogen and progesterone
◼ They are responsible for:
◼ Maturation of the reproductive organs
◼ Appearance of secondary sexual characteristics
◼ Breast development and cyclic changes in the uterine
mucosa
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Gonads
Male: Testes
◼ Testes located in an extra-abdominal sac (scrotum)
produce testosterone
◼ Testosterone:
◼ Initiates maturation of male reproductive organs
◼ Is necessary for sperm production
◼ Maintains sex organs in their functional state
◼ Causes appearance of secondary sexual characteristics and
sex drive
◼ Increases muscle and skeletal mass
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Pineal Gland
◼Small gland hanging from the roof of the third
ventricle of the brain
◼Secretory product is melatonin
◼Melatonin is involved with:
◼Day/night cycles
◼Physiological processes that show rhythmic
variations (body temperature, sleep, appetite)
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*Thymus
◼Usually seen in infants and children, the
thymus diminishes in adulthood.
◼*Normal development of the immune
response is due to hormones secreted by it.
◼Hormonal product e.g. Thymosin which is
essential for the normal development of T
lymphocytes and the immune response
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Fill in the Table:
Hormone Endocrine Gland Function
1. Insulin
2. Glucagon
3. Oxytocin
4. Parathyroid
5. Epinephrine
6. Cortisol
7. Throxine
8. Growth Hormone
9. Adrenocorticotropic
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