hormones of posterior pituitary and related disorders
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HORMONES OF POSTERIOR PITUITARYHORMONES OF POSTERIOR PITUITARYAND RELATED DISORDERSAND RELATED DISORDERS
LEARNING OBJECTIVESLEARNING OBJECTIVES
At the end of the lecture the student should be able to know the
Overview of the posterior pituitary
The function of Oxytocin and ADH
Disorders of ADH
Clinical correlate
THE PITUITARY GLANDTHE PITUITARY GLAND The pituitary gland is often portrayed as the "master gland" of the
body
Secretes a battery of hormones that collectively
influence all cells and affect virtually all physiologic
processes
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PITUITARY GLAND (HYPOPHYSIS)PITUITARY GLAND (HYPOPHYSIS)
Lies in the sella turcica, a bony cavity at the base of the brain
Connected to the hypothalamus by the pituitary (or hypophysial) stalk
Anterior Pituitary (adenohypophysis)
Posterior pituitary (neurohypophysis)
POSTERIOR PITUITARY HORMONESPOSTERIOR PITUITARY HORMONES
Antidiuretic
hormone
Kidney Conservation of body
water
Oxytocin Uterus,
Breast
Stimulates milk ejection
and uterine contractions
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SITE OF SYNTHESIS OF HORMONES OFSITE OF SYNTHESIS OF HORMONES OFPOSTERIOR PITUITARYPOSTERIOR PITUITARY
Synthesized in hypothalamus
ADH primarily in Supraoptic
Oxytocin primarily in Paraventricular nucleus
Neurohormones
Stored and released form posterior pituitary
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EFFECT OF LESION OF POSTERIOR PITUITARYEFFECT OF LESION OF POSTERIOR PITUITARY
Loss of Posterior Pituitary results in only a TRANSIENT deficiency if
hypothalamic function(cell bodies that synthesize ADH) remains
intact
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OXYTOCINOXYTOCIN
Breast-feeding
Contracts the myoepithelial cells of the alveoli
Classic neuroendocrine reflex
Childbirth (parturition)
In late pregnancy, uterine smooth muscle (myometrium) becomes
sensitive to oxytocin
Positive feedback
CONTROL OF OXYTOXIN SECRETIONCONTROL OF OXYTOXIN SECRETION
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POSITIVE FEEDBACKPOSITIVE FEEDBACK
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CONTROL OF ADH RELEASECONTROL OF ADH RELEASE
Osmotic pressure
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secretion parallels osmotic pressure.
Volume effects
as ECF drops, ADH secretion increases
Baroreceptor mediated.
Others
pain, trauma, emotion, alcohol.
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REGULATION OF ADHREGULATION OF ADH
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ACTIONS OF ADHACTIONS OF ADH
1. Antidiuretic actions
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Increases permeability of the collecting ducts to water
V2 receptors
2. Vasopressor actions
constricts vascular smooth muscle cells
V1 receptors, non-hormonal
ACTION OF ADHACTION OF ADH
Main target is Renal Collecting Duct
Increases permeability by increasing water channels (Aquaporins)
Water absorbed PASSIVELY
Urea can pass with water
ELECROLYTES CANNOT PASS with water
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ACTION OF ADHACTION OF ADH
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DISORDERS OF ADH SECRETIONDISORDERS OF ADH SECRETION
Diabetes Insipidus
Syndrome of Inappropriate Appropriate Antidiuretic Hormone
Secretion (SIADH)
DIABETES INSPIDUSDIABETES INSPIDUS
TYPES
Central Diabetes Insipidus
Insufficient ADH to effect renal collecting tubules
Nephrogenic Diabetes Insipidus
Inability of KIDNEYS to respond to ADH
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CAUSES OF CENTRAL DICAUSES OF CENTRAL DI
Damage to pituitary or hypothalamus
Surgery
Tumor
Illness
Head Injury
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NEPHROGENIC DIABETES INSIPIDUSNEPHROGENIC DIABETES INSIPIDUS
Defect in the kidneys tubules
Inherited (genetic) disorder or a chronic kidney disorder.
Certain drugs, such as lithium and tetracycline
CAUSES OF SIADHCAUSES OF SIADH
Central nervous system disease
Pulmonary disease
Carcinoma (Lung)
Drugs
Surgery
Idiopathic
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ReferencesReferences
1. Textbook of Medical Physiology. Eleventh Edition. Guyton
2. Syndrome of Inappropriate Antidiuretic Hormone Secretion. Bora
K, Chaudhry M.
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3. Causes. By Mayo Clinic staff.
http://www.mayoclinic.com/health/diabetes-
insipidus/DS00799/DSECTION=causes
http://www.mayoclinic.com/health/diabetes-insipidus/DS00799/DSECTION=causeshttp://www.mayoclinic.com/health/diabetes-insipidus/DS00799/DSECTION=causeshttp://www.mayoclinic.com/health/diabetes-insipidus/DS00799/DSECTION=causeshttp://www.mayoclinic.com/health/diabetes-insipidus/DS00799/DSECTION=causes