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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

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