1. Thyroid Gland On each side of trachea is lobe of thyroid
Weighs 1 oz & has rich blood supply

2. Photomicrograph of Thyroid Gland

3. Copyright 2009, John Wiley & Sons, Inc.

4. 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 ,and growth
increases sympathetic activity
Parafollicular cells or C cells produce calcitonin
Lowers blood Ca2+ by inhibiting bone resorption
Copyright 2009, John Wiley & Sons, Inc.

5. Actions of Thyroid Hormones
T3 & T4 = thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production

6. 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.

7. 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.

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

10. 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
increases sympathetic activity
Parafollicular cells or C cells produce calcitonin
Lowers blood Ca2+ by inhibiting bone resorption
Copyright 2009, John Wiley & Sons, Inc.

11. Actions of Thyroid Hormones
T3 & T4 = thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production
Calcitonin = responsible for building of bone & stops reabsorption of bone (lower blood levels of Calcium)

12. Parathyroid Glands
4 pea-sized glands found on back of thyroid gland

13. 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.

14. Parathyroid Hormone
Raise blood calcium and Mg levels (decrease HPO4) -2 )
increase activity of osteoclasts
increases reabsorption of Ca+2 by kidney
increase loss of phosphate (HPO4) -2 in urine
promote formation of calcitriol (vitamin D3) by kidney which increases absorption of Ca+2, HPO4 and Mg+2 by intestinal tract
Opposite function of calcitonin

15. 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

17. Adrenal Glands One on top of each kidney
3 x 3 x 1 cm in size and weighs 5 grams
Cortex produces 3 different types of hormones from 3 zones of cortex
Medulla produces epinephrine & norepinephrine

18. Structure of Adrenal Gland
Cortex derived from mesoderm
Medulla derived from ectoderm

19. 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 “hydrocortisone”, corticosterone and cortisone
Androgens have masculinzing effects
Dehydroepiandrosterone (DHEA) only important in females
Adrenal medulla
Modified sympathetic ganglion of autonomic nervous system
Intensifies sympathetic responses
Epinephrine and norepinephrine
Copyright 2009, John Wiley & Sons, Inc.

20. Mineralocorticoids 95% of hormonal activity due to aldosterone
Functions
increase reabsorption of Na+ with Cl- , bicarbonate and water following it
promotes excretion of K+ and H+
Hypersecretion = tumor producing aldosteronism
high blood pressure caused by retention of Na+ and water in blood

21. Regulation of Aldosterone

22. Glucocorticoids 95% of hormonal activity is due to cortisol
Functions = help regulate metabolism
increase rate of protein catabolism & lipolysis
conversion of amino acids to glucose
stimulate lipolysis
provide resistance to stress by making nutrients available for ATP production
raise BP by vasoconstriction
anti-inflammatory effects reduced
reduce release of histamine from mast cells
decrease capillary permeability
depress phagocytosis
Decrease tissue repair

23. Adrenal Medulla
Chromaffin cells receive direct innervation from sympathetic nervous system
develop from same tissue as postganglionic neurons
Produce epinephrine & norepinephrine
Hormones are sympathomimetic
effects mimic those of sympathetic NS
cause fight-flight behavior
Acetylcholine increase hormone secretion by adrenal medulla

24. Copyright 2009, John Wiley & Sons, Inc.