1. Copyright 2009, John Wiley & Sons, Inc.
The Endocrine System
Copyright 2009, John Wiley & Sons, Inc.

2. Objectives Thyroid gland hormones: function and clinical importance.
Parathyroid gland hormones and role in calcium homeostasis.
Adrenal gland hormones: function and clinical importance.
Pinal gland hormone: function and clinical importance.
Thymus and pancreatic islet hormones: function and clinical importance.
Prostaglandins.

3. Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland
Located inferior to larynx
2 lobes connected by isthmus
Thyroid follicles produce thyroid hormones
Thyroxine or tetraiodothyronine (T4)
Triiodothyronine (T3)
Both increase BMR, stimulate protein synthesis, increase use of glucose and fatty acids for ATP production
Para follicular cells or C cells produce calcitonin
Lowers blood Ca2+ by inhibiting bone resorption
Copyright 2009, John Wiley & Sons, Inc.

4. Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland
Copyright 2009, John Wiley & Sons, Inc.

5. Control of thyroid hormone secretion
Thyrotropin-releasing hormone (TRH) from hypothalamus
Thyroid-stimulating hormone (TSH) from anterior pituitary
Situations that increase ATP demand also increase secretion of thyroid hormones
Copyright 2009, John Wiley & Sons, Inc.

6. Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones 1
Anterior
pituitary
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones 1 2
Anterior
pituitary
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones 1 2 3
T3 and T4
released into
blood by
follicular cells
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones 1 2 3 4
T3 and T4
released into
blood by
follicular cells
Elevated
T3inhibits
release of
TRH and
TSH
(negative
feedback)
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones 1 2 3 5 4

8. Copyright 2009, John Wiley & Sons, Inc.
Parathyroid Glands
Embedded in lobes of thyroid gland
Usually 4
Parathyroid hormone (PTH) or parathormone
Major regulator of calcium, magnesium, and phosphate ions in the blood
Increases number and activity of osteoclasts
Elevates bone resorption
Blood calcium level directly controls secretion of both calcitonin and PTH via negative feedback
Copyright 2009, John Wiley & Sons, Inc.

9. Copyright 2009, John Wiley & Sons, Inc.
Parathyroid Glands
Copyright 2009, John Wiley & Sons, Inc.

10. Copyright 2009, John Wiley & Sons, Inc.
Roles of Calcitonin, Parathyroid hormone, Calcitrol in Calcium Homeostasis
Copyright 2009, John Wiley & Sons, Inc.

11. 1
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
Low level of Ca2+ in blood
stimulates parathyroid
gland chief cells to release
more PTH.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level.
PARATHYROID HORMONE (PTH)
promotes release of Ca2+ from
bone extracellular matrix into
blood and slows loss of Ca2+
in urine, thus increasing blood
Ca2+ level. 3 4 2 1
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT. 1
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
Low level of Ca2+ in blood
stimulates parathyroid
gland chief cells to release
more PTH.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level. 3 2 1
CALCITRIOL stimulates
increased absorption of
Ca2+ from foods, which
increases blood Ca2+ level.
PTH also stimulates
the kidneys to release
CALCITRIOL.
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
Low level of Ca2+ in blood
stimulates parathyroid
gland chief cells to release
more PTH.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level.
PARATHYROID HORMONE (PTH)
promotes release of Ca2+ from
bone extracellular matrix into
blood and slows loss of Ca2+
in urine, thus increasing blood
Ca2+ level. 3 4 2 5 6 1
PTH also stimulates
the kidneys to release
CALCITRIOL.
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
Low level of Ca2+ in blood
stimulates parathyroid
gland chief cells to release
more PTH.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level.
PARATHYROID HORMONE (PTH)
promotes release of Ca2+ from
bone extracellular matrix into
blood and slows loss of Ca2+
in urine, thus increasing blood
Ca2+ level. 3 4 2 5 1
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level. 2

12. Copyright 2009, John Wiley & Sons, Inc.
Adrenal Glands
2 structurally and functionally distinct regions
Adrenal cortex
Mineralocorticoids affect mineral homeostasis
Glucocorticoids affect glucose homeostasis
cortisol
Androgens have masculinizing effects
Dehydroepiandrosterone (DHEA) only important in females
Adrenal medulla
Modified sympathetic ganglion of autonomic nervous system
Intensifies sympathetic responses
Epinephrine and norepinephrine (Catecholamines)
Copyright 2009, John Wiley & Sons, Inc.

13. Copyright 2009, John Wiley & Sons, Inc.
Adrenal Glands
Copyright 2009, John Wiley & Sons, Inc.

15. Copyright 2009, John Wiley & Sons, Inc.
Pancreatic Islets
Both exocrine and endocrine gland
Roughly 99% of cells produce digestive enzymes
Pancreatic islets or islets of Langerhans
Alpha or A cells secrete glucagon – raises blood sugar
Beta or B cells secrete insulin – lowers blood sugar
Delta or D cells secrete somatostatin – inhibits both insulin and glucagon
F cells secrete pancreatic polypeptide – inhibits somatostatin, gallbladder contraction, and secretion of pancreatic digestive enzymes
Copyright 2009, John Wiley & Sons, Inc.

16. Copyright 2009, John Wiley & Sons, Inc.
Pancreas
Copyright 2009, John Wiley & Sons, Inc.

17. Negative Feedback Regulation of Glucagon and Insulin
Copyright 2009, John Wiley & Sons, Inc.

18. Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULIN
GLUCAGON 1 5 2 3 4 6
Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
Blood glucose level falls
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULIN
GLUCAGON 1 5 2 3 4 6 7
Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
If blood glucose continues
to fall, hypoglycemia
inhibits release of
insulin
Blood glucose level falls
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULIN
GLUCAGON 1 5 2 3 4 6 7 8
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
GLUCAGON 1 5 2 3 4
INSULIN
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON 1 2 3 4
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON 1 2
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON 1 2 3
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete 1
GLUCAGON

19. Copyright 2009, John Wiley & Sons, Inc.
Ovaries and Testes
Gonads – produce gametes and hormones
Ovaries produce estrogens (estradiol and Estrone) and progesterone
With FSH and LH regulate menstrual cycle, maintain pregnancy, prepare mammary glands for lactation, maintain female secondary sex characteristics
Inhibin inhibits FSH
Relaxin produced during pregnancy
Testes produce testosterone – regulates sperm production and maintains male secondary sex characteristics
Copyright 2009, John Wiley & Sons, Inc.

20. Copyright 2009, John Wiley & Sons, Inc.
Pineal Gland
Attached to roof of 3rd ventricle of brain at midline
Masses of neuroglia and pinealocytes
Melatonin – amine hormone derived from serotonin
Appears to contribute to setting biological clock
More melatonin liberated during darkness than light
Copyright 2009, John Wiley & Sons, Inc.

21. Thymus and Other Endocrine Tissues
Located behind sternum between the lungs
Produces thymosin, thymic humoral factor (THF), thymic factor (TF), and thymopoietin
All involved in T cell maturation
Copyright 2009, John Wiley & Sons, Inc.

22. Autocrine Chemical Signals
Autocrine chemical signals include the chemical mediators of inflammation.
Prostaglandins
Thromboxanes
Prostacyclins
Leukotrienes
Collectively known as eicosanoids.

23. Autocrine Chemical Signals
These products are released from injured cells.
Responsible for initiating some of the symptoms of inflammation.
Pain receptors are stimulated directly by prostaglandins.

24. Prostaglandins
Essential fatty acid deficiency and omega-6:omega-3 imbalance is linked with the following serious health conditions:
Heart attack
Cancer
Insulin resistance
Asthma
Lupus
Schizophrenia
Depression
Stroke
Obesity
Diabetes
Arthritis
Alzheimer’s Disease