Transcript The endocrine system

THE ENDOCRINE SYSTEM
FELIX K. NYANDE
The endocrine system
• A collection of glands that secrete hormones.
• Hormones are released into circulation
to
arrive at a target organ.
• The target organ has cells that possess the
appropriate receptor(s)
• The system use cycles and negative feedback
to regulate physiological functions
Major endocrine Glands
1. Hypothalamus
2. Pituitary: anterior and posterior
3. Thyroid
4. Parathyroid
5. Pancreas
6. Ovaries
7. Testes
8. Adrenals: medulla and cortex
Hypothalamus
O Releasing and inhibiting hormones that
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control the release of pituitary hormones.
Corticotropin-releasing hormone (CRH)
Thyrotropin-releasing hormone (TRH)
Growth hormone-releasing hormone
(GHRH)
Gonadotropin-releasing hormone
(GnRH)
Vasopressin and oxytocin
HYPOTHALAMUS
Hormone
ADH
Function
Increases water
reabsorption by kidney
Oxytocin
• Stimulates contraction
of pregnant uterus,
• milk ejection from
breasts after childbirth
Pituitary gland
(hypophysis)
O Also known as ‘the master gland’
O Located
in the skull beneath the
hypothalamus of the brain
O Divided into the anterior and posterior
glands
O Posterior gland stores hormones from the
hypothalamus
Anterior pituitary
• Growth hormone (GH)
• Adrenocorticotropic hormone
(ACTH)
• Thyroid-stimulating hormone
(TSH)
• Follicle-stimulating hormone
(FSH)
• Luteinizing hormone (LH)
HYPOTHALAMUS
LH
Female: stimulates OVULATION and
development of corpus luteum to
produce estrogen and progesterone
Male:
stimulates
secretion
of
testosterone, development of interstitial
tissue of testes
ANTERIOR PITUITARY
Hormone
GH
prolactin
Function
Stimulates growth of bone and muscle,
promotes protein synthesis and fat
metabolism, decreases carbohydrate
metabolism
stimulates the production of breast milk.
ACTH
Stimulates synthesis and secretion of
adrenal cortical hormones
TSH
Stimulates synthesis and secretion
of thyroid hormones
Female: stimulates growth of ovarian follicle,
Adrenal
cortex
Mineralocorticoids e.g.
Aldosterone
Glucocorticoids e.g.
Cortisol
Androgens e.g.
testosterone
Increases sodium absorption,
potassium loss by kidney
Affects metabolism of all
nutrients; regulates blood
glucose levels, affects
growth, has anti-inflammatory
action, and decreases effects of
stress
Have minimal intrinsic
androgenic activity
Adrenal medulla
• Epinephrine
• Norepinephrine
• Function:
Serve
as
neurotransmitters
for
the
sympathetic nervous system
Thyroid gland
Hormone
Function
T3 & T4
Increase metabolic rate; increase
protein and bone turnover; increase
responsiveness to catecholamines;
necessary for foetal and infant growth
and development.
Calcitonin
Reduces the concentration of calcium
and phosphate in the blood by aiding
the absorption of calcium into the
matrix of bones
Parathyroid gland
Parathyroid hormone
Function:
• Regulates serum calcium by
stimulating oesteoclasts to break
down the calcium containing
matrix to release free calcium
ions into the bloodstream.
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pancreas
Insulin
Lowers blood glucose by
facilitating glucose transport
across cell membranes of
muscle, liver, and adipose
tissue
Glucagon
Increases blood glucose
concentration by stimulation of
glycogenolysis and
glyconeogenesis
gonads
Testes
development of male sex organs
(testosterone) and
secondary
sex
characteristics; aids in sperm
production
Ovaries
Affects development of female
(oestrogen sex organs and secondary sex
&
characteristics.
progesteron Influences menstrual cycle;
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stimulates growth of uterine wall;
maintains pregnancy
Disorders of the posterior
pituitary
• ADH and oxytocin are synthesized in the hypothalamus
and stored in the posterior pituitary.
• Vasopressin controls the excretion of water by the
kidney; its secretion is stimulated by an increase in the
osmolality of the blood or by a decrease in blood
pressure.
• Oxytocin facilitates milk ejection during lactation and
increases the force of uterine contractions during labor
and delivery. Oxytocin secretion is stimulated during
pregnancy and at childbirth.
Disorders of the anterior
pituitary
O Hypersecretion:
• ACTH: Cushing’s syndrome
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growth hormone: acromegaly. Acromegaly, an excess of
growth hormone in adults, results in bone and soft
tissue deformities and enlargement of the viscera
without an increase in height.
In children: gigantism, with a person reaching 7 or 8 feet
tall.
Hyposecretion
Grow hormone: dwarfism
ADH: diabetes insipidus:
causes
O Hypopitutarism:
• disease of the pituitary gland itself or of the
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hypothalamus,
destruction of the anterior lobe of the pituitary gland
Panhypopituitarism
(Simmonds’ disease): total absence of all pituitary
secretions and is rare.
Postpartum pituitary necrosis (Sheehan’s syndrome)
radiation therapy to the head and neck area.
Total destruction of the pituitary gland by trauma,
tumor, or vascular lesion
General manifestations
• extreme weight loss, emaciation,
• Atrophy of all endocrine glands and organs,
• hair loss,
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impotence,
amenorrhea,
hypometabolism, and
hypoglycemia.
Coma and death occur if the missing
hormones are not replaced.
Diabetes insipidus
O Diabetes insipidus is a disorder
of the posterior lobe of the
pituitary gland caused by a
deficiency
of
antidiuretic
hormone (ADH), or vasopressin
and characterised by polydipsia
and large volumes of dilute urine
causes
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head trauma,
brain tumor,
surgical ablation or irradiation of the pituitary gland.
Infections of the central nervous system (meningitis, encephalitis,
tuberculosis)
Other tumours (eg, metastatic disease, lymphoma of the
breast or lung).
failure of the renal tubules to respond to ADH; this nephrogenic
form may be related to hypokalemia, hypercalcemia, and a variety
of medications
(eg, lithium, demeclocycline
Clinical manifestations
• very dilute, water-like urine with a
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specific gravity of 1.001 to 1.005
The urine contains no abnormal
substances such as glucose and
albumin.
patient tends to drink 2 to 20 liters of
fluid daily
hypernatremia
severe dehydration.
Diagnostic investigations
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Fluid deprivation test: carried out by withholding
fluids for 8 to 12 hours or until 3% to 5% of the body
weight is lost. The patient is weighed frequently
during the test. Plasma and urine osmolality studies
are performed at the beginning and end of the test.
The inability to increase the specific gravity and
osmolality of the urine is characteristic of diabetes
insipidus.
Measurements of plasma levels of ADH
(vasopressin) and plasma and urine osmolality, trial
of desmopressin (synthetic vasopressin) therapy
intravenous infusion of hypertonic saline solution.
management
• The objectives of therapy are to
• replace ADH
• ensure
adequate
fluid
replacement,
• identify
and
correct
the
underlying
intracranial
or
Nephrogenic pathology.
management
O PHARMACOLOGIC THERAPY
• Desmopressin (intranasal or IM)
management
• inform the patient and family about follow-up
care and emergency measures.
• provide specific verbal and written instructions,
• show the patient how to administer the
medications
• advise the patient to wear a medical
identification bracelet and to carry medication
and information about this disorder at all times.