Endocrine system

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1 Endocrine system maintains homeostasis:
2 Growth, maturation, reproduction, energy,
metabolism (physical and chemical changes that
(physical
takes place w/i an organism), behavior

1 Composed of glands or glandular tissue:
2 Synthesize, store, and secrete hormones

1 Endocrine-
Endocrine-glands /or cells are ductless but
highly vascular; secretion hormones into
bloodstream

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HORMONES
1 Hormones: natural chemical substances
secreted
1 Carried in bloodstream to “target”
cells/tissues
1 Effects are direct or indirect
2 Trophic/tropic-
Trophic/tropic- stimulate another endocrine
gland

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1 What are hormones?
1 Hormones are organic chemical
messengers produced and secreted by
endocrine cells into the bloodstream.
Hormones regulate, integrate and control
a wide range of physiologic functions.

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Characteristics:

1 Circulate in blood at low concentrations

1 Secreted in minute amounts at variable rates

1 Bind to specific receptors/cells

1 Variable effects on rates of responses

1 Most not stored, must be produced as needed

1 Activity is of short duration
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Actions of Hormones
1 Fetal development and differentiation
1 Cell growth
1 Metabolism
1 Cardiovascular function
1 Renal function
1 Skeletal function
1 Reproductive function
1 Immune function
1 Central nervous system function

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SECRETION
1 Pituitary-target
Pituitary- gland axis: pituitary gland
regulates endocrine glands thru tropic
hormones. Tropic hormones get feedback
about specific target glands by constant
monitoring of levels of hormone.
1 Works by stimulation or inhibition of
hormones

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SECRETION
1 Hypothalamic-pituitary-target-gland
Hypothalamic-pituitary-target- axis:
axis:
hypothalamus in brain’s di-encephalon
di-
produces tropic hormones; in particular the
pituitary gland. In turn, pituitary controls
other target glands to produce hormones.
Therefore works indirectly
1 Hypothalamus secretes releasing factors
and inhibiting factors

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FEEDBACK MECHANISMS
1 Negative-
Negative- increased levels of substance inhibit
hormone synthesis and secretion; decreased
levels stimulate production and release (heat
thermostat)
1 Positive- increased levels stimulate hormone
Positive-
production and release; decreased levels inhibit
synthesis and secretion
1 Complex- thyroid stimulating hormone (TSH) in
Complex-
pituitary is activated by thyroid releasing hormone
(TRH) and inhibited by somatostatin (in
hypothalamus). Decreased T3 T4 leads to
increased TSH release. Increased levels lead to
inhibit TSH secretion

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DYSFUNCTIONS
DEFINITIONS
1 HYPERFUNCTION:
HYPERFUNCTION: excessive hormone
production/function
1 HYPOFUNCTION: deficient hormone
HYPOFUNCTION:
function/production
1 HYPERTROPHY: increase in size of
organ, in bulk not in # of cells or tissue
elements as a result of increased function
1 HYPERPLASIA: excessive proliferation of
normal cells in normal tissue arrangement
of an organ
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THE
PITUITARY
(HYPOPHYSIS)

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THE PITUITARY
1 The pituitary is located just below the brain,
and this location is crucial for its function.
1 The part of the brain in direct contact with
the pituitary is the hypothalamus, but neural
pathways mediate influences of other parts
of the brain on the pituitary.
1 As described in the above figure (including
the legend!), the pituitary in the human
consists of two lobes: the anterior pituitary
(adenohypophysis), and the posterior lobe.

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1 The posterior lobe is also referred to as “the
neurohypophysis”. However, these two terms are
not entirely synonymous, as will be explained
later.
1 Anatomically, the pituitary is connected to the
hypothalamus by the stalk, a “stem” much thinner
than the pituitary itself.
1 The interrelation of the two parts of the pituitary
with the brain is different in nature.
1 The endocrine cells of the anterior pituitary are
epithelial. There are five types of
adenohypopyseal cells, each specializing in
producing one or two hormones, all of them
proteins or long polypeptides.

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1 Of the six hormones of the anterior pituitary
discussed in this course, four are tropic (trophic)
hormones, namely, hormones whose central target
organ is an endocrine gland.
1 The hypothalamus regulates the anterior pituitary
cells via neurohormones, produced by
hypothalamic neurons. The hypothalamic
hormones are secreted from the nerve endings of
these neurons (i.e., from the end of their axons).
1 They then diffuse into the portal system (branched
blood vessels), which brings them to the anterior
pituitary cells.
1 The hypothalamic hormones are cell-type specific.
cell-
Most of the hypothalamic hormones are
stimulatory, but there are several inhibitory ones as
well.

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1 The anterior pituitary has five types of cells-
cells-
somtotrophs, thyrotrophs, gonadotrophs,
lactotrophs and corticotrophs. These cells
secrete seven hormones.

1 The two hormones secreted from the
posterior pituitary are vasopressin (or anti
diuretic hormone – ADH), and oxytocin.

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HORMONE TARGET PRINCIPAL ACTIONS
TISSUE
$8 LIVER Stimulates liver, muscle,
'8 cartilage, bone, and other tissues
$8 promote growth of body cells,
(8 protein synthesis, tissue repair.
9$
BE8 THYROID Stimulates synthesis and secretion
)$ 8 GLAND of thyroid hormones by thyroid
$8B9 gland.
B8
* 8 OVARIES In females initiates development
)$ 8 TESTES of oocytes and induces ovarian
$8*9 secretion of estrogens. In males
stimulates testes to produce
sperms.
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TISSUE
+,8 OVARIES In females , stimulates secretion of
$8 TESTES estrogens and progesterone, ovulation
+ and formation of corpus luteum. In
males stimulates production of
testosterone.
- 8 MAMMARY Together with other hormones
-6+8 GLANDS promotes milk secretion
E ADRENAL Stimulates secretion of glucocorticoids
8 CORTEX by adrenal cortex.
$8
5B8
C 8 BRAIN May influence brain activity.
)$ 8
$8
C9
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TISSUE

4.84B8 UTERUS Stimulates contraction of
MAMMARY smooth muscles of
GLANDS uterus during child birth,
stimulates milk ejection

D)))8 KIDNEYS Decreases urine volume,
88 SWEAT decreases water loss
E8 GLANDS through perspiration,
$8 raises blood pressure by
ARTERIOLES
3 constricting arterioles

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ANTERIOR PITUITARY
DYSFUNCTIONS
1 HYPOPITUITARYISM: caused by deficiency of one
or more of hormones. Decreased production of all
hormones is rare, but referred to as
panhypopituitarism
1 More commonly, one or two deficiencies are
present
1 ACTH: Adrenocorticotropic hormone*
1 TSH: thyroid stimulating hormone*
1 **Most life-threatening
life-
1 Deficiencies of gonadotropins (LH,FSH) change
sexual function in men and women
1 Testicular failure in men, ovarian failure in women
1 Lags in puberty, amenorrhea, and infertility
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ANTERIOR PITUITARY
1 GROWTH HORMONE: changes tissue
growth indirectly
1 May lead to dwarfism (growth retardation),
hypoglycemia, and delayed wound healing
1 In adults, leads to decreased bone
density, (osteoporosis) pathological
fractures, decreased muscle strength, and
increased cholesterol

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HYPERPITUITARYISM
1 GROWTH HORMONE: produce gigantism or
acromegaly
2 Gigantism: excess hormone occurs before puberty
causing rapid proportional growth in bone length.
Height 6’6”
2 Most die early with infection or trauma.
2 Acromegaly: occurs after puberty producing skeletal
thickness, hypertrophy of skin, enlarged visceral organ
like liver and heart.
• Enlarged hands, feet, Para nasal and frontal sinuses,
deformities of spin and mandible, enlarged tongue, speech
difficulties, hoarseness, hypertension, oily skin, and joint pain
• Cardiomegaly leads to CHF
• GH is an insulin antagonist leading to hyperglycemia
• Stimulate adrenal cortex- Cushing’s Disease
cortex-

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POSTERIOR PITUITARY
1 HYPOFUNCTION: responsible for ADH
and oxytocin
1 Deficiency of ADH- DIABETES INSIPIDUS
ADH-
DI
1 123456758498ABC758D7CBE4F23D
3 1757B376818F7B638C48623CBF857BF8CEF738
4C857CB228ABC75
3 B5784FD7384985278757C7684F52B
3 B332786765BC248
3 C2DFBC738C253C85734373

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POSTERIOR PITUITARY
1 HYPERFUNCTION
1 Oversecretion
of ADH - SYNDROME OF
INAPPROPRIATE ADH (SIADH)

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DWARFISM

ACROMEGALY
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THYROID
GLAND

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• The butterfly shaped thyroid gland is located
in front of the trachea, in the frontal neck. It is
symmetrical, consisting of two lobes
connected with a narrower “bridge” (Isthmus).
• The normal mass of thyroid gland is 30 gms.
• The thyroid’s basic structural unit is the
follicle: a sphere made of one layer of
epithelial endocrine cells.
• The main products of the follicular cells are
the thyroid hormones: T4 (tyroxine, or
tetraiodothyronine) and T3 (triiodothyronine).
• A few cells called parafollicular / C cells lie
between follicles. They produce hormone
calcitonin.

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Follicular cell

C cell
(parafollicular)

Basolateral (Basal)
membrane
Apical membrane
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Thyroid gland hormones
HORMONE PRINCIPAL ACTIONS

B/8 Increases basal metabolic rate,
0E18 stimulate synthesis of proteins,
B2808.18 increase use of glucose, fatty
acids, increase lipolysis,
accelerate body growth.
5 805B18 Lowers blood levels of ionic
calcium, phosphorus

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THYROID
1 Functions:
2 Metabolism: increase rate, accelerate food utilization for
energy, excites mental processes
2 Growth: in children accelerates growth
2 Carbohydrate: stimulates metabolism, including insulin
secretion
2 Fat: enhances fat metabolism
2 Body wt: production relates inversely to body wt (does not
stimulate appetite)
2 CV: causes vasodilation, increased cardiac output and heart
rate, increased systolic B/P by 10-20 mm but diastolic may
10-
drop the same
2 Respiration: increases O2 use, rate, and depth
2 GI: increases appetitie, absorption,motility
2 CNS: speeds mental processes

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Hyperthyroidism
2 Involves excessive hormone production
2 Leads to hyper metabolism

2 Signs and symptoms: thyrotoxicosis

2 Stimulates heart, protein synthesis,
breakdownbuildup leading to negative nitrogen
balance (degradation); hyperglycemia; increased
fat metabolism
1 Grave’s disease: toxic diffuse goiter
disease:
1 Most common
1 Strikes women, 20-30.
20-
1 Multi system syndrome, affecting eyes, skin, bones
1 Increased thyroid hormone as well as goiter

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Hypothyroidism
2 Deficiency in thyroid hormone
2 Leads to low metabolism with build-up of metabolites
2 Metabolites with water accumulate within cells, cause edema, called
Myxedema
2 Myxedema coma: rare but can occur; heart becomes flabby,
chambers increase in size, CO decreases; life threatening; high
mortality rate
1 3 TYPES:
2 HYPOTHYROIDISM: adult onset; tissue destruction is most probable
cause
2 CRETINISM:
• Profound hypothyroidism in infants
• All developmental aspects are retarded
• Severe brain damage can occur
• If caught early, can prevent retardation
2 JUVENILE HYPOTHYROIDISM:
• Begins during childhood, Hashimoto’s disease, caused by drugs,
autoimmune
• Affects growth and sexual maturation
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THYROID CANCER
CONGENITAL RETROSTERNAL
HYPOTHYROIDISM

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PARATHYROID GLANDS
1 Partially embedded un posterior surface of
lateral lobes of thyroid glands are several small
round masses of tissue called parathyroid
glands.
1 Each parathyroid gland has a mass of 40 mg.
1 Usually one superior and one inferior
parathyroid gland is attached to each lateral
thyroid lobe.
1 Parathyroid has 2 type of cells – chief cells and
oxyphil cell.

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1 Parathyroid hormone corrects calcium deficiency by
promoting calcium conservation by kidneys, stimulating
calcium release by bone, enhance calcium absorption
from GI, reduce serum phosphate levels.
1 Works on negative feedback control
1 In kidneys, causes calcium to be reabsorbed with release
of phosphorus
1 Stimulates kidneys to convert Vit D to a metabolite that
allows for PTH to work on bone
1 In bone, helps convert osteoblasts to osteoclasts,
promoting bone breakdown and release of calcium.
1 Acts on GI to stimulate absorption of calcium (must have
calcitriol).
1 Calcitonin from thyroid causes inhibition of Ca++ release
from bones

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Parathyroid gland hormones
HORMONE PRINCIPAL ACTIONS

-E8 Increases blood Ca and Mg levels
$8 decreases blood phosphate level
0-B18 promotes vita.D production.

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Parathyroid dysfunctions
1 Hyperparathyroidism:
lead to increased
calcium and decreased phosphorus.

1 Hypoparathyroidism:too little PTH leading
to decreased calcium and increase
phosphorus.

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Hyperparathyroidism
Hypothyroidism

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ADRENAL GLANDS

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ADRENAL GLANDS
1 The paired adrenal ( suprarenal ) glands, one of which
lies superior to each kidney, have a flattened pyramidal
shape.
1 In an adult each adrenal gland is 3-5 cm in height, 2-3
cm in width and 1 cm thick. Weighs about 3.5-5 gms.

1 The adrenal gland has 2 different parts- a large
peripherally located adrenal cortex, small centrally
located adrenal medulla.
1 The adrenal medulla has chromaffin cells which produce
epinephrine and norepinephrine.
1 The adrenal cortex is sub divided into 3 zones.
2 Zona glomerulosa – outer zone secretes mineralocorticoids
2 Zona fasciculata - middle wider zone secretes glucocorticoids.
2 Zona reticularis – inner zone secretes androgens/ sex
hormones.

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HORMONE SOURCE PRINCIPAL ACTIONS

C Zona Increase blood levels of
E)8 glomerulosa Na, water decreases K
( Zona Increases protein
E) fasciculata breakdown, stimulate
lipolysis, dampen
inflammation
E)8 Zona Assist in early growth of
reticularis axillary and pubic hair, in
females libido.
18 Adrenal Fight-or-flight, increase in
38 medulla heart rate, contraction,
blood pressure, blood flow,
glucose level.
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ADRENAL DYSFUNCTIONS
1 Cushing’s syndrome: hypercortisolism
1 Cortisol excess
1 Affects more women than men
1 ADRENAL GLAND INSUFFICIENCY: ADDISON’S
-Suppressed adrenocortical function and
hormones
1 May precipitate “adrenal crisis”: life-threatening
life-
1 ALDOSTERONISM-
ALDOSTERONISM- Excessive secretion of
mineralocorticoids, especially aldosterone

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Cushing’s Syndrome

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PANCREAS
1 Pancreas is both endocrine as well as
exocrine gland.
1 The pancreas is 12.5-15 cm in length.
12.5-
1 It is located in curve of duodenum.
1 It has a head, body and tail.
1 Scattered among the exocrine acini are 1- 1-
2 millions tiny clusters of endocrine tissue
called pancreatic islets or islets of
langerhans.

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( 8 Alpha Raises blood glucose level
cells
A cells
7) 8 Beta cells Lowers blood glucose level
B cells
9$) Delta Inhibits secretion of insulin
cells and glucagon
D cells
-8 F cells Inhibits Somatostatin
E secretion.

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Hormones of the Ovaries

1))#8 ovary Regulate female reproductive
) cycle, oogenesis, maintain
pregnancy, promote
development of feminine
secondary sex characters
6 .8 ovary Flexibility of pubic symphysis
dilation uterine cervix

7%8 ovary Inhibits secretion of FSH
from anterior pituitory.

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Hormones of the Testes
B))8 Testes Stimulates descent of
testes before birth,
regulates
spermatogenesis,
promotes maintains
masculine secondary sex
characters.
7%8 Testes Inhibits secretion of FSH
from anterior pituitary.

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Endocrine system

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