Download Pituitary gland (hypophysis cerebri)

Regulation of blood
glucose
Endocrine regulation of blood glucose
-The normal blood glucose level ranges between 80-120
mg/100 ml blood.
-This level is controlled by the following hormones:
1- Pancreatic h.
2- Adrenaline.
3- Glucocorticoids.
4-Thyroxine.
5-Growth h.
Importance of blood glucose regulation:
!!!
• Glucose is the only nutrient that normally
can be used by the brain and retina.
• Glucose is important source of energy for the
cells.
a) Pancreatic hormones
-The endocrine cells of the pancreas are
present in discrete groups called ‘islets of
Langerhan’s’, which are more numerous in
the tail than in the body
and comprise 1-2% of
its weight.
Four groups of cells are now identified in
the islets:
1.Alpha cells,( 25% of islet mass)  glucagon h.
2.Beta cells,(about 60%), located in the centre of
the islet.  insulin h.
3.Delta or D cells, (10% of the islet mass) 
somatostatin h.
4.F
cells,
(only
polypeptide h.
about
5%)
pancreatic
I. Insulin
1-Insulin  blood glucose level by:
a. Glycogenesis
b. Inhibition of glycogenolysis
c. glucose uptake by the tissues
d-gluconeogenesis
5.  transformation of glucose into fat.
2-Anabolic action
Insulin is an essential hormone for growth:
a)In muscle, insulin stimulates the uptake of certain
amino acids across the cell membrane.
b)Insulin also stimulates the rate of protein synthesis.
c) Anti-catabolic effects i.e. it inhibits proteolysis.
2.Insulin increases cellular uptake of potassium,
phosphate and magnesium.
3.It
increases
the
reabsorption
of
phosphate and sodium by renal tubules
potassium,
Regulation of secretion
-The major regulation is the plasma glucose level
(no insulin when glucose < 50 mg%).
-A half maximum insulin secretion occurs at a
plasma glucose level of about 150 mg% and a
maximum response at 300 to 500 mg%.
- GIP
(glucose
dependent
peptide),
gastrin,
secretin,
pancreatic glucagons
insulinotropic
Cholecystokinin,
- Oral protein, Triglycerides and fatty acids
II. Glucagon
-Glucagon is a hyperglycemic polypeptide from α
cells.
1.glucose:glycogenolysis andgluconeogenesis
2.lipolysis and hepatic cholesterol synthesis.
4.Natriuresis, by renal tubular Na+ reabsorption
5. myocardial contractility  COP.
6.A local CNS h. for regulation of appetite.
1. Glucagon release is stimulated by:
a) Hypoglycaemia  2-4 fold  in glucagon level.
b) Protein meal
c)  FFA.
d) Exercise.
e)Vagal stimulation or administration of acetylcholine.
f)Stress, including infection, toxaemia, burns and
major surgery.
g) Growth hormone.
2. Glucagon release is inhibited by
a)Hyperglycaemia:
50%.
b)  FFA.
c) Somatostatin.
glucagon
level
by
B) Other hormones which regulate blood
glucose level
1.Adrenaline:
-glycogenolytic on liver and muscles.
2.Glucocorticoids:
I-  gluconeogenesis.
II-  glucose uptake by the tissues.
3.Growth hormone:
- glucagon hormone.
-Inhibits glucose uptake by tissues.
4.Thyroxin:
- glucose absorption from intestine.
- glycogenolysis.
The net result is a rise in blood glucose level.
Danger of increased blood glucose:
(Diabetes Mellitus)
• 2 forms of diabetes mellitus:
–Type I: insulin dependent diabetes
(IDDM).
–Type II: non-insulin dependent
diabetes (NIDDM).
Diabetes Mellitus
Diabetes mellitus
It results from deficiency of insulin action , which
leads to:
1.Hyperglycaemia:
- due to absence of effects of insulin.
2.Glucosuria: i.e loss of glucose in urine.
- when the blood glucose level becomes >
renal threshold (180 mg%).
3.Polyuria due to:
a)Excretion of glucose in urine.
b) osmotic pressure
of the blood drags water out of the cells
towards the blood.
-This causes dehydration of the tissue cells.
4.Polydepsia:intense thirst due to dehydration.
5. Acidosis:
- Due to inhibition of carbohydrate metabolism.
-The body depends on the fat metabolism
which supplies most of the energy needed.
-Uncontrolled diabetes  accumulation of
acetoacetic acid and beta hydroxybuteric acid
 acidosis.
6.Loss of weight and asthenia:
-Due to mobilization of fat and proteins for
supply of energy.
7. cholesterol and TG in blood:
- early development of arteriosclerosis.
Pituitary gland
(hypophysis cerebri)
-The pituitary gland is an ovoid structure weighing
between 500 and 600 mg in an adult.
-It is located at the base of the brain in a small cavity
called 'pituitary fossa' or 'sella tursica', which is
covered by an extension of the dura mater (the
diaphragma sellae) through which passes the pituitary
stalk connecting the gland to the hypothalamus.
Growth hormone
Functions of growth hormone
1-On growth:
a) It has a powerful protein anabolic effect.
b) It increases the length of bones.
2-On metabolism:
1) Protein metabolism.
2) CHO metabolism.
3) Lipid metabolism.
Functions of growth hormone
1. On metabolism  Protein metabolism
Growth hormone stimulates protein synthesis by:
i-  AA transport through the cell membranes.
ii- Increase of protein synthesis by ribosomes.
iii- Increase formation of RNA.
iv- Inhibition of protein catabolism.
Functions of growth hormone
2- On metabolism  CHO metabolism
anti-insulin action:
- It inhibits the hexokinase enzyme and so
decreases glucose uptake by tissues.
- It stimulates gluconeogenesis in the liver with
more production of glucose.
- It stimulates the release of glucagon hormone
Functions of growth hormone
3- On metabolism  lipid metabolism
-It
has
powerful
lipolytic
effect
thus
increasing the blood level of FFA which
provides energy during stress conditions
particularly hypoglycaemia and starvation.
Mechanism of growth hormone action:
-Its growth promoting actions are mediated by a
group of polypeptides called somatomedins that
formed in the liver, in bone cells
-They are structurally similar to proinsulin. They
are, called insulin-like growth factors (IGF), of
which 2 types have been identified: IGF-I and IGF-II.
Control of G.H. secretion
I. Hypothalamus
1.GH releasing factor which increases GH
secretion.
2.GH release inhibiting factor or somatostatin
which suppresses GH secretion.
Physiology of growth
-Body growth is a continuing process throughout
childhood and adolescence.
-It is exceedingly rapid in the first 2 years of life
-Later there is a second phase of rapid growth in
relation to puberty followed by cessation of
growth when the adult height is reached.
Peaks of growth
Factors affecting growth
1. Hormones.
2. Extrinsic factors.
3. Genetic factors.
4. Growth-regulating peptides.
Factors affecting growth
1-Hormones
a)Growth hormone promotes growth in infancy.
b) Thyroid hormones stimulate the process of physical,
mental and sexual growth growth probably by a permissive
action for somatomedins.
c) Insulin is important for the formation of somatomedins.
d) Androgens, and oestrogen, are responsible for second spurt of
growth at puberty because of their strong anabolic effect
2. Extrinsic factors:
-Balanced diet which is particularly rich in
proteins and essential vitamins is important
for a normal growth process particularly in
children.
-Exposure to stress as infections in children
leads to suppression of growth.
-This is followed in the recovery period, by a
stage of enhanced growth rate called “catchup period”.
3. Genetic factors:
-which determine:
- Growth rate.
- Age of puberty.
- Adult height.
4. Growth-regulating peptides:
I-Fibroplast growth factors.
II-epidermal growth factors
III-Growth promoting and growth inhibiting
peptides.
Disorders of adenohypophysis
Disorders of GH
 Secretion
Before
union of
epihhysis
Gigantism
After
union of
epihhysis
Acromegaly
 Secretion
In children
In adults
Dwarfism
 Muscle
mass
Broad forehead
Prognathism
Functions of prolactin
1.Development of breast tissue:
a) During prepubertal and postpubertal:
- Proliferation and branching of milk ducts.
b) During pregnancy, prolactin:
- development of milk alveoli.
c) After parturition:
-milk synthesis and secretion.
2.In women, high levels of prolactin appear to
block the synthesis and release of LHRH 
preventing ovulation.
-This accounts for the absence of menstruation
(amenorrhea) during postpartum lactation.
Osmoreceptors
Supraoptic n.
Of hypothalamus
ADH
320
310
300
290
m.osm/l
Osmotic
control
of ADH
Blood vessel
H2O reabsorption
2-Vasoconstriction (vasopressin)
2.When administered systemically in large
doses, ADH causes contraction of the smooth
muscles particularly in the blood vessels 
intense splanchnic vasoconstriction.
-Used therapeutically in controlling persistant,
serious gastrointestinal bleeding.
Disorders of ADH secretion
Diabetes insipidus (D.I):
A clinical condition caused by  ADH actions.
Types and causes:
1) Central D.I:
-due to deficiency of ADH release from the
hypothalamus.
2) Nephrogenic D.I:
-due to inability of the kidney to respond to ADH due to
receptor defect.
a)Polyuria:The
volume
of
urine
increased (may reach 25 liters/day)
b)Polydepsia
is
markedly
 PRIH
 Oxytocin
1. Milk-letting effect
 Prolactin
 Oxytocin
Milk secretion
and ejection
Suckling
reflex
2. Powerful contraction in the uterus
-Powerful contracting action on the uterus,
-This effect is potentiated by oestrogen and
inhibited by progesterone.
Thyroid Gland
 Found at the base of the throat
 Consists of two lobes and a connecting
isthmus
 Produces two hormones
 Thyroid hormone
 Calcitonin
Thyroid Hormone
 Major metabolic hormone: increase
lipolysis, blood glucose level, increase
metabolic rate
 Composed of two active iodinecontaining hormones
 Thyroxine (T4) – secreted by thyroid
follicles
 Triiodothyronine (T3) – conversion of T4 at
target tissues
Adrenal Glands
 Two glands
 Cortex – outer glandular region in three
layers
 Medulla – inner neural tissue region
 Sits on top of the kidneys
Hormones of the Adrenal Cortex
 Mineralocorticoids (mainly aldosterone)
 Produced in outer adrenal cortex
 Regulate mineral content in blood, water,
and electrolyte balance
 Target organ is the kidney
 Stimulate Na and water reabsorption.
Hormones of the Adrenal Cortex
 Glucocorticoids (including cortisone and
cortisol)
 Produced in the middle layer of the adrenal
cortex
 Promote normal cell metabolism
 Help resist long-term stressors
 Released in response to increased blood
levels of ACTH
Hormones of the Adrenal Cortex
 Sex hormones
 Produced in the inner layer of the adrenal
cortex
 Androgens (male) and some estrogen
(female)
Hormones of the Adrenal Medulla
 Produces two similar hormones
(catecholamines)
 Epinephrine
 Norepinephrine
 These hormones prepare the body to
deal with short-term stress