Page 120 - Clinical Biochemistry

2- Oxytocin
 Both of them are synthesized in the hypothalamus, they are then transported to the posterior
pituitary gland via the neuro-hypophysial capillaries.
 In the posterior pituitary gland, their synthesis is completed and stored here until they are
ready to be released into the circulation.
1-Antidiuretic Hormone (ADH).
• ADH is a peptide of 9 amino acids. It is also known as arginine vasopressin.
• ADH acts on the collecting ducts of the kidney to facilitate the reabsorption of water into
the blood.
• It acts to reduce the volume of urine formed.
• A deficiency of ADH leads to excessive loss of urine, a condition known as diabetes
insipidus.
• The most severely affected patients may urinate as much as 10-15 liters of urine each day.
• The disease is accompanied by terrible thirst, and patients must continually drink water to
avoid dangerous dehydration.
2-Oxytocin:
• It is a peptide of 9 amino acids.
• It acts on certain smooth muscles:
- Stimulating contractions of the uterus at the time of birth.
- Stimulating release of milk when the baby begins to suckle.
• Oxytocin is often given to prospective mothers to accelerate birth.
3- Thyroid Gland
• The thyroid gland is located in the lower front part of the neck.
• Secretes thyroid hormone, which regulates the body's overall metabolism
• 90% T4 and 10% T3
• Affect growth and maturation of tissues, cell metabolism, heat production, oxygen
consumption.
• It plays a role in bone growth and development of the brain and nervous system in children.
• It helps maintain normal blood pressure, heart rate, digestion, muscle tone, and reproductive
functions.
(A) T4 and T3
 T4 is a derivative of the amino acid tyrosine with four atoms of iodine.
• In target cells (e.g. liver cells), one atom of iodine is removed from T4 converting it into
triiodothyronine (T3).