The Endocrine System
Glands and Hormones
Anatomy & Physiology II
Chapter 12
Endocrine System Components
endocrine system - glands, tissues, and cells
that secrete hormones
 endocrinology – the study of this system and
the diagnosis and treatment of its disorders

endocrine glands – organs that are traditional
sources of hormones
 hormones - chemical messengers that are
transported by the bloodstream and stimulate
physiological responses in cells of another tissue
or organ, often a considerable distance away

Endocrine Organs
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Thymus
Adrenal gland
Pancreas
Parathyroid
glands
Posterior
view
Trachea
Gonads:
Ovary (female)
Testis (male)

major organs of endocrine system
The Endocrine System
Consists of a group of glands that
produce hormones
 Works with nervous system to control
and coordinate all other body systems
 Affects body systems by chemical stimuli

Hormones
Chemical messengers with regulatory effects on
cells or organs
 Hormones from endocrine glands are released
directly into tissue fluids; not through ducts
 Some affect many tissues
◦ Growth hormone
◦ Thyroid hormone
◦ Insulin
 Some affect a specific tissue (target tissue)
◦ Thyroid-stimulating hormone (TSH)
◦ Adrenocorticotropic hormone (ACTH)

Hormone Chemistry
Amino acid compounds
◦ Proteins or related compounds
◦ All hormones except steroids
 Lipids
◦ Made of fatty acids
◦ Most are steroids, derived from the steroid
cholesterol
◦ Produced in adrenal cortex and sex glands
◦ Prostaglandins are also lipids

Hormone Regulation

Negative feedback (most common)
◦ Endocrine gland oversecretes hormone
◦ Tissue becomes too active
◦ Tissue negatively effects gland to decrease
secretion

Positive feedback
◦ Hormone response produces more hormone

Rhythmic pattern
Other Hormone Secreting Tissues
Tissues other than endocrine glands also
secrete hormones
 Brain
 Digestive organs
 Kidney
The Endocrine Glands
The Pituitary
Pituitary (hypophysis) gland
 Master gland
 Releases hormones that affect working of
other glands
 Controlled by hypothalamus
The hypothalamus, pituitary gland,
and target tissues
Arrows indicate the
hormones’
target issues and
feedback
pathways.
ZOOMING IN
• What two structures
does the
infundibulum
connect?
Control of the Pituitary
Hypothalamus
 Sends releasing hormones (RH) and
inhibiting hormones (IH)
◦ Hormones stimulate and suppress anterior
pituitary secretions

Produces antidiuretic hormone (ADH)
and oxytocin
◦ Stored in posterior pituitary
◦ Nerve impulses stimulate secretions
Control of Pituitary: Feedback from
Target Organs

1
-
TRH
+
5
6
Negative feedback
inhibition
-
4
Target organs
2
negative feedback increased target organ
hormone levels inhibits
release of hormones
+
• positive feedback -
TSH
Thyroid hormone
+
3
+
–
Stimulatory effect
Inhibitory effect
stretching of uterus
increases OT release,
causes contractions,
causing more stretching
of uterus, etc. until
delivery
Hormones of the Anterior Lobe

Growth hormone (GH) or somatotropic

Thyroid-stimulating hormone (TSH) or
thyrotropic

Adrenocorticotropic hormone

Prolactin (PRL)

Gonadotropins
◦ Follicle-stimulating hormone (FSH)
◦ Luteinizing hormone (LH)
Hormones of the Posterior Lobe
Antidiuretic hormone (ADH)
 Oxytocin

Tumors of the Pituitary

Excessive number of tumor growth
hormone (GH) cells in childhood
◦ Gigantism

Overactive GH-producing tumor cells in
adulthood
◦ Acromegaly

Tumors that destroy secreting tissues
◦ Underactivity
The Thyroid Gland

Largest endocrine gland

Lateral lobes on either side of larynx

Connecting band (isthmus)

Enclosed by connective tissue capsule
Hormones of the Thyroid Gland

Thyroxine (T4)
◦ Principle hormone
◦ Increases energy and protein metabolism rate

Triiodothyronine (T3)
◦ Increases energy and protein metabolism rate

Calcitonin
◦ Regulates calcium metabolism
◦ Works with parathyroid hormone and vitamin D
Thyroid Gland Disorders

Hypothyroidism
◦ congenital hypothyroidism (decreased TH)
 hyposecretion present a birth (formerly cretinism)
◦ myxedema (decreased TH)
◦ adult hypothyroidism
◦ treat with oral thyroid hormone
 Hyperthyroidism
◦ Graves disease
◦ Thyroid storm
 Thyroiditis
◦ Hashimoto disease
Thyroid Gland Disorders

goiter – any pathological enlargement of the
thyroid gland
◦ endemic goiter
 dietary iodine deficiency, no TH, no - feedback,
increased TSH stimulates hypertrophy
◦ toxic goiter (Graves disease)
 autoantibodies mimic the effect of TSH on the
thyroid causing hypersecretion
 overgrown thyroid produces functional TH
Endemic Goiter
Tests of Thyroid Function

Blood tests
◦ Uptake of radioactive iodine
◦ Thyroid-stimulating hormone level

Oral radioactive iodine to measure
accumulation in thyroid
The Parathyroid Glands
Four glands in posterior capsule of thyroid
 Secrete parathyroid hormone (PTH)

◦ Works with calcitonin to regulate calcium
metabolism
Calcium Metabolism
Calcium balance requires
 Calcitriol (dihydroxycholecalciferol)
◦ Produced by modifying vitamin D in liver then
in kidney
Parathyroid hormone
 Calcitonin

Disorders of the Parathyroid Glands

Tetany
◦ Inadequate production of parathyroid
hormone (PTH)

Fragile bones and kidney stones
◦ Excess production of parathyroid hormone
(PTH)
The Adrenal Glands
Two small glands on top of kidneys
 Each gland has two parts that act as
separate glands

◦ Medulla
◦ Cortex
Hormones from the Adrenal
Medulla
Fight-or-flight hormones
 Epinephrine (adrenaline)
 Norepinephrine (noradrenalin)
Hormones from the Adrenal
Cortex

Glucocorticoids
◦ Cortisol or hydrocortisone

Mineralocorticoids
◦ Aldosterone

Sex hormones
Disorders of the Adrenal Cortex

Addison disease
◦ Hypofunction of adrenal cortex

Aldosteronism
◦ Hyperfunction of adrenal cortex resulting in
excess secretion of aldosterone

Cushing syndrome
◦ Hypersecretion of cortisol

Adrenogenital Syndrome (AGS)
◦ Hypersecretion of adrenal androgen
Adrenal Disorders

Cushing syndrome - excess cortisol secretion
◦ hyperglycemia, hypertension, weakness, edema
◦ rapid muscle and bone loss due to protein catabolism
◦ abnormal fat deposition
 moon face and buffalo hump
Adrenal Disorders

adrenogenital syndrome
(AGS)
◦ adrenal androgen hypersecretion
(accompanies Cushing)
◦ enlargement of external sexual
organs in children and early
onset of puberty
 newborn girls exhibit masculinized
genitalia
◦ masculinizing effects on women
 increased body hair, deeper voice
and beard growth
The Pancreas and Its Hormones
Islets of Langerhans are specialized pancreas
cells that secrete
 Insulin
◦ Lowers blood sugar level
◦ Stimulates protein synthesis (manufacture of
amino acids into protein)

Glucagon
◦ Increases blood sugar
Pancreas
Tail of pancreas
Bile duct
Pancreatic islet
Exocrine acinus
PancreaticDuodenumHead of
ducts
pancreas
Beta cell
Alpha cell
Delta cell
Pancreatic islet
c: © Ed Reschke

exocrine digestive gland and endocrine cell clusters (pancreatic
islets) found retroperitoneal, inferior and posterior to stomach.
Pancreatic Hormones

1-2 million pancreatic islets (Islets of Langerhans)
produce hormones
◦ other 98% of pancreas cells produces digestive enzymes

Insulin - secreted by B or beta () cells
◦ secreted during and after meal when glucose and amino
acid blood levels are rising
◦ stimulates cells to absorb these nutrients and store or
metabolize them lowering blood glucose levels
 promotes synthesis glycogen, fat, and protein
 suppresses use of already stored fuels
 brain, liver, kidneys and RBCs absorb glucose without insulin, but
other tissues require insulin
◦ insufficiency or inaction is cause of diabetes mellitus
Pancreatic Hormones
glucagon – secreted by A or alpha () cells
◦ released between meals when blood glucose concentration is
falling
◦ in liver, stimulates gluconeogenesis, glycogenolysis, and the
release of glucose into the circulation raising blood glucose
level
◦ in adipose tissue, stimulates fat catabolism and release of free
fatty acids
◦ glucagon also released to rising amino acid levels in blood,
promotes amino acid absorption, and provides cells with raw
material for gluconeogenesis
 Somatostatin - secreted by D or delta () cells
◦ partially suppresses secretion of glucagon and insulin
 gastrin - secreted by G cells
◦ stimulates stomach acid secretion, motility and emptying22

Pancreatic Hormones

hyperglycemic hormones raise blood glucose
concentration
◦ glucagon, growth hormone, epinephrine,
norepinephrine, cortisol, and corticosterone

hypoglycemic hormones lower blood glucose
◦ insulin
Diabetes Mellitus

most prevalent metabolic disease in world
◦ disruption of metabolism due to hyposecretion or
inaction of insulin
◦ symptoms:
 polyuria (excess urine output), polydipsia (intense
thirst) and polyphagia (hunger)
 revealed by elevated blood glucose, glucose in urine and
ketones in the urine

transport maximum – limit to how fast the
glucose transporters can work to reabsorb
◦ excess glucose enters urine and water follows it
 causes polyuria, dehydration, and thirst
Types of Diabetes Mellitus

Type 1 (IDDM) – 5 to 10% of cases in US
◦ insulin is always used to treat Type 1
 insulin injections, insulin pump, or dry insulin inhaler
 monitoring blood glucose levels and controlled diet
◦ autoantibodies attack and destroy pancreatic beta cells

Type 2 (NIDDM) – 90 to 95% of diabetics
◦ problem is insulin resistance
 failure of target cells to respond to insulin
◦ risk factors are heredity, age (40+),obesity, and ethnicity
◦ treated with weight loss program and exercise since:
 loss of muscle mass causes difficulty with regulation of glycemia
 adipose signals interfere with glucose uptake into most cells
◦ oral medications improve insulin secretion or target cell
sensitivity
Pathology of Diabetes

pathogenesis:
◦ cells cannot absorb glucose, must rely on fat and
proteins for energy needs
 weight loss and weakness
◦ fat catabolism increases free fatty acids and
ketones in blood
 ketonuria promotes osmotic diuresis, loss of Na+ and K+,
irregular heartbeat, and neurological issues
 ketoacidosis occurs as ketones decrease blood pH
 deep, gasping breathing and diabetic coma are terminal result
Pathology of Diabetes

chronic pathology (chronic hyperglycemia)
◦ leads to neuropathy and cardiovascular damage
from atherosclerosis and microvascular disease
 arterial damage in retina and kidneys (common in type I),
atherosclerosis leads to heart failure (common in type II)
 diabetic neuropathy – nerve damage from impoverished
blood flow can lead to erectile dysfunction, incontinence,
poor wound healing, and loss of sensation from area
Metabolic Syndrome

Also called syndrome X or insulin-resistance
syndrome

Related to type 2 diabetes

High state of hyperglycemia and obesity

Caused by insulin resistance in combination with
high plasma glyceride levels, low HDL levels, and
hypertension

Treated with weight loss, diet, exercise; drugs to
lower blood pressure and cholesterol; drugs to
lower insulin resistance
The Sex Glands
Ovaries and testes produce hormones to
 Develop sexual characteristics
 Maintain reproductive organs
Hormones of the Sex Glands
 Male
sex hormone
◦ Testosterone
 Female
sex hormones
◦ Estrogen
◦ Progesterone
The Thymus Gland
Mass of lymphoid tissue in upper chest
superior to heart
 Important in development of immunity
 Produces thymosin

◦ Assists in maturity of T lymphocytes
The Pineal Gland
Cone-shaped structure posterior to
midbrain
 Produces melatonin

◦ Influences sleep–wake cycles
◦ Appears to delay onset of puberty
Other Hormone-Producing Tissues
Substances that regulate body actions are
also produced by

Stomach

Small intestine

Kidneys

Brain

Atria of heart

Placenta
Prostaglandins
Group of hormones made by most body
tissues
 Produced, act, and rapidly inactivated in or
close to origin
 Constrict structures
 Dilate structures
 Promote inflammation
Hormones and Treatment
Hormones are extracted from animal tissue,
manufactured in the lab, or genetically engineered

Growth hormone

Insulin

Adrenal steroids

Epinephrine (adrenaline)

Thyroid hormones

Oxytocin

Androgens

Estrogen and progesterone
Hormones and Stress
Stress response involves both nervous and
endocrine system
 Hormones released during stress help body
cope
 Unchecked levels of hormones can harm
body
Aging and the Endocrine System

Pancreas
◦ Adult-onset diabetes mellitus

Thyroid
◦ Decreased hormone secretion

Pituitary
◦ Decreased bone mass
End of Presentation