ANTIDIURETIC HORMONE

1. 1
Vasopressin
Anti Diuretic Hormone (ADH)
Introduction
The anti diuretic hormone (ADH) is the
hormone of the posterior pituitary gland.It
prevents excessive urine production.
Source of secretion
ADH is secreted mainly by supra optic
nucleus of hypothalamus and in small
quantity by paraventricular nucleus.

2. 2
Chemical Nature and Half-Life
• ADH is a polypeptide, containing 9 amino acids.
Its half-life is about 18-20 minutes.
Transport
• It is transported from the supra optic nuclei to
nerve-endings in the posterior pituitary gland by
carrier proteins called neurophysins.
Mechanism of Action
• Action through intracellular mediator.

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Action of ADH
• On kidneys
– It increases the permeability of the collecting
tubules and ducts to water, increasing water
absorption from the luman of the collecting
tubules and ducts. It conserves water in the
body, so less water in the urine.

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On vascular smooth muscle/Vasopressor
Action
• ADH shows constrictor action on blood vessels,
particularly the arteries. It causes constriction of
the arteries in all part of the body. Due to the
vasoconstriction, the blood pressure (B.P)
increases.
Other actions
• It causes the contraction of all smooth muscles
in body such as the GIT, Bile duct, and uterus.

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Regulation of ADH
• Factors increasing ADH secretion:
• Increased Na+ conc.
• Increased osmolality of the ECF.
• Low blood volume, low B.P.
• pain,emotion,exercise,anxiety.
• Nausea, vomiting.
Drugs
– morphine, nicotine,barbiturates,anesthetics.

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Factors decreasing ADH secretion
• Decreased Na+ conc.
• Decreased osmolality of ECF.
• Increased blood volume.
• Increased B.P.
• Alcohol.

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Disorders related with ADH:
Diabetes inspidus:
• This is a syndrome characterized by passage of
large volumes of dilute urine due to the absence
of ADH.
Causes:
• This occurs when the supra optic hypophysial
system fails to secrete ADH.It may be due to:

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• Lesions of the supra optic nuclei.
• Tumors of the hypothalamus.
• Inflammation, as in encephalitis, basal meningitis, and
syphilis result in destruction of part of the hypothalamus.
Characteristics:
• Poly uria:6-8 liters of urine is produced per day b/c of
decreased ADH secretion.
• Poly dipsia: Increase thirst.
Treatment
• It may be treated by injecting ADH suspended in oil.