Uploaded by na.117bakhtawar.ali

Endocrine system - 2

Endocrine system
Dr. Sadat A. Aziz
The pituitary gland:
It consists of two major portions,
1. The posterior pituitary gland
2. The anterior pituitary gland
The hormones of the anterior pituitary gland:
• They are in turn regulated by releasing
hormones which are secreted from the
hypothalamus and get to the anterior pituitary
gland through blood.
 Growth hormone (GH)
It is released by the anterior pituitary
gland, it promotes growth through:
a. Increases the rate of protein
b. Stimulates cell division and mitosis.
c. It stimulates growth and wound
Disorders of the growth hormones:
1. Pituitary dwarfism:
Hyposecretion of GH during childhood results in an abnormal growth
rate (a final height of only 3 to 4 feet) with a symmetric and normal body
This condition is treatable if it is diagnosed properly at the early stages
of life.
2. Giantism (or gigantism): Hypersecretion of GH during childhood
leads to this condition which is characterised by excessive growth of the
long bones and the person may attain a height of 8 feet
3. Acromegaly:
• it is a clinical condition resulted from hypersecretion of GH in an adult,
• it is mainly caused by a pituitary gland lesion such as tumour.
• This condition is characterised by disproportionately growth of the facial bones, the
hands and feet.
• Also the skin becomes thicker, and the tongue may protrude
• It is secreted by anterior pituitary gland.
• The secretion of prolactin can be regulated
by breast-feeding.
• Functions:
• It initiates and maintains milk production
by the mammary glands.
Other hormones of the anterior pituitary gland:
• Follicle-Stimulating Hormone
• Luteinizing Hormone
The pancreas:
It extends from the curve of
spleen. The pancreas is
considered an exocrine and
endocrine gland.
The pancreatic endocrine function
The hormone-producing cells of the pancreas are called
islets of Langerhans
it is secreted by alpha cell of pancreas in response to
hypoglycemia, a low blood glucose level.
• It stimulates the process of gluconeogenesis,
enhances liver to change glycogen to glucose and
increases fats and excess amino acids turn over to
• So it raises the blood glucose level.
• it secreted by beta cells of pancreas in response to hypergycemia, high blood glucose level.
It increases the glucose up take by the cells.
• In addition, it stimulates the liver and skeletal muscles to change glucose to glycogen
• A deficiency of insulin hormone or its dysfunction is led to a condition called diabetes
Types of diabetes mellitus:
1. Diabetes mellitus type I: due to insulin hormone deficiency
2. Diabetes mellitus type II: resulted from defects in insulin receptors
Somatostatin: It is released by delta cells and decreases secretion of both insulin and glucagon
Adrenal glands:
• The two adrenal glands are each located on top of
a kidney.
• Each adrenal gland consists of two parts: an inner
adrenal medulla and an outer adrenal cortex.
Adrenal medulla:
The cells of the adrenal medulla secrete catecholamines
(epinephrine and norepinephrine) in response to stress
situation and prepare body for “fighting or flight”.
Adrenal cortex: The adrenal cortex secretes three
(aldosterone), glucocorticoids (cortisol), and sex
hormones (estrogens and androgens).
 Aldosterone: Aldosterone stimulate
reabsorption of sodium and water,
and the excretion of potassium by
the kidney tubules.
 Cortisol: It is secreted in response to several
physiological stress situations such as disease,
physical injury, fear, anger, exercise, and hunger.
Functions of cortisol:
1. Cortisol increases the use of fats and excess
amino acids (gluconeogenesis) for energy and
decreases the use of glucose.
2. Cortisol also has an anti-inflammatory effect.
The thyroid gland is located on the front and sides of the trachea just below the larynx and is shaped somewhat
like a butterfly.
It produces thyroxine (T4) and triiodothyronine (T3).
These hormones regulate the metabolic rate and the activity of the brain, muscles, heart, and virtually all
other organs.
Disorders associated with thyroid hormones:
Goiters: resulted from iodine defficiency, characterised by thyroid gland enlargement.
Cretinism: hyposecretion of thyroid hormone in new-born leads to development of this condition
characterised by a sever physical and mental disabilities.
Grave`s disease: resulted from hypersecretion of thyroid hormone, characterised by an increase in the
metabolic rate, weight loss, excessive sweating, fatigue and exophthalmos.
Parathyroid gland:
It secrets parathyroid hormone in response to
• Function:
reabsorption, reducing renal excretion, and
increasing bone resorption of calcium.
Para-follicular cells of the thyroid gland:
• They are involved in the synthesis and secretion of
calcitonin in response to hypercalcemia.
in general, has effects opposite to those of
parathyroid hormone tends to decrease plasma
calcium concentration by enhancing calcium
deposition in the bone, increasing calcium