1. Pituitary Gland Disorders
Diabetes Insipidus (DI) is very different from the disease called sugar diabetes (diabetes mellitus)
DI is caused by the insufficient release of ADH from the neurohypophysis. Without ADH acting on the collecting ducts in the kidneys, the normal urine output of 1–1.5 liters per day increases to over 2.5 liters per day and dehydration and hypernatremia results

2. The Thyroid Gland
The butterfly-shaped thyroid gland is located inferior to the larynx and anterior to the trachea. It has two laterally placed lobes separated by a bridge-like isthmus

3. The Thyroid Gland
Most of the thyroid gland is composed of spherical groups of follicular cells called thyroid follicles
The follicles store
a 100-day supply
of its two hormones
in an inactive
gel-like substance
called TGB (for
thyroglobulin)

4. Thyroid Hormones
TGB is a large glycoprotein made from the oxidation and iodination of molecules of the amino acid. tyrosine
The two hormones released
from TGB are:
thyroxine or T4
(tetraiodothyronine)
and T3
(triiodothyronine)

5. Thyroid Hormones
In the blood, T3 and T4 are bound to pre-albumins, albumin, and a specific carrier protein called thyroid-binding globulin (TBG)
Most T4 released from the thyroid is converted “peripherally” (by enzymes in the blood) into T3 , which is a more active hormone
Together with hGH and insulin, thyroid hormones accelerate body growth, particularly the growth of the nervous and skeletal systems

6. Thyroid Hormones
Thyroid-stimulating hormone (TSH) is released by the anterior pituitary gland in response to TRH secreted into the portal system
The hypothalamus
responds to higher
circulating levels of
T3 and T4 via negative
feedback to inhibit
TRH secretion

7. Thyroid Hormone Regulation 1 2 3 5 4 1 2 3 4 1 2 3 1 2 1 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
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
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
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
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
Thyroid Hormone
Regulation

8. Thyroid Hormones
A goiter is an enlargement of the thyroid gland and may be associated with hyperthyroidism, hypothyroidism, or euthyroidism
In many third-word countries
dietary iodine intake is inadequate;
the resultant low level of thyroid
hormone in the blood stimulates
secretion of TSH, which causes
thyroid gland enlargement

9. The Parathyroid Glands
The parathyroid glands are small, round masses of tissue attached to the posterior surface of the lateral lobes of the thyroid gland
There are usually two
parathyroid glands
attached to each
lobe of the thyroid,
one superior and one inferior

10. Parathyroid Hormones
Calcitonin (Thyrocalcitonin) is made by the parafollicular (C-cells) of the thyroid gland and
when secreted lowers the blood calcium level
An increase in blood calcium will stimulate the C-cells of the thyroid to secrete calcitonin
Increased calcitonin will cause a negative feedback inhibition of parathyroid hormone (PTH) which
causes a decrease in blood calcium and an increase in blood phosphate levels

11. PARATHYROID HORMONES (Interactions Animation)
Calcitonin
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12. Parathyroid Hormones
Parathyroid hormone (PTH) is made by the more numerous chief (principal) cells of the gland
PTH increases absorption
of Ca2+ from the GI tract
and stimulates osteoclastic
activity so that Ca2+ is
released from bone into
the blood

13. PARATHYROID HORMONES (Interactions Animation)
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14. Calcium Regulation 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.
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.
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
High level of Ca2+ in blood
stimulates thyroid gland
parafollicular cells to
release more CT.
CALCITONIN inhibits
osteoclasts, thus decreasing
blood Ca2+ level. 2 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
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

15. The Adrenal Glands
There are two adrenal glands, one superior to each kidney (also called the suprarenal glands). During embryonic development, the adrenal glands differentiate into two structurally and functionally distinct regions
the adrenal cortex
the adrenal medulla
Steroid hormones like cortisol
Catecholamines like norepinephrine

16. The Adrenal Glands

17. The Adrenal Cortex
The adrenal cortex is peripherally located and makes up 80-90% of the total weight of the gland
The cortex is subdivided into three zones, each of which secretes a different group of steroid hormones, all formed
from the cholesterol
molecule

18. Adrenocortical Hormones
Just deep to the CT capsule, the cells of the zona glomerulosa synthesize mineralocorticoid hormones
The middle zone, or zona fasciculata, secrete mainly glucocorticoid hormones,
primarily cortisol
The inner zona reticularis
is the site of synthesis
of weak androgens
(masculinizing hormones)

19. Adrenocortical Hormones
Mineralocorticoids regulate the concentrations of Na+ and K+ in the blood (affects blood volume/pressure)
Aldosterone is the major hormone in this group
Glucocorticoids influence glucose metabolism and the ability to resists the effects of stress
Cortisol is the major hormone in this group
Weak androgens (masculinizing sex hormones) have little effect in men, but play an important role in promoting libido in women

20. RAAS
The most important effects of aldosterone is seen in the renin-angiotensin-aldosterone system (RAAS)
The RAAS is stimulated by a decrease in blood volume and/or blood pressure – as in cases of dehydration or hemorrhage. Low BP stimulates juxtaglomerular cells
in the kidney to
secrete the
enzyme renin

21. RAAS
Renin converts the plasma protein angiotensinogen (produced in the liver) into angiotensin I. As angiotensin I circulates to the lungs, an enzyme called angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II
Angiotensin II stimulates the adrenal cortex to secrete aldosterone (salt and H20 resorption indirectly increases BP), and it is a
potent vasoconstrictor (which
directly increases BP)

22. RAAS

23. Glucocorticoids
Glucocorticoids (mainly cortisol) regulate metabolism by promoting the breakdown of proteins and fats to form glucose (gluconeogenesis). Increased blood sugar levels assist the body to cope with stress
Their inflammatory effects result from inhibiting white blood cells. Unfortunately they also retard tissue repair and slow wound healing
glucocorticoids are very useful in the treatment of chronic inflammatory disorders such as Lupus, though long term side-effects are severe