Endocrinology introduction, hypothalamus and pituitary gland Physiology

1. ENDOCRINOLOGY
INTRODUCTION,
HYPOTHALAMUS AND
PITUITARY GLAND
DR ZAHRA HAQ

2. ENDOCRINOLOGY
Definition:
Study of hormones secreted by ductless glands is called endocrinology.
Hormone:
A chemical substance, secreted by a cell or group of cells into body fluids that exerts
physiological control over other cells of body.

3. DIFFERENCE BETWEEN HORMONE AND FACTOR
Factor Hormone
A substance that has action of
hormone but not purified or identified
as a distinct chemical compound is
called a factor.
When a factor has been purified and
identified as a distinct chemical compound,
it is known as a hormone

4. HYPOTHALAMUS
 It secretes many chemical compounds, that control secretion of pituitary glands but unfortunately, they
are not labelled as hormone.
 They are labelled as factors.
 Hypothalamic factors are involved in control of pituitary hormones.
 For every pituitary hormone, hypothalamus secretes two factors:
• Stimulating factor
• Inhibiting factor

5. HYPOTHALAMUS

6. PITUITARY GLAND
Also called hypophysis.
Diameter is 1cm.
Weight is 0.5 to 1 gram.
• It has 2 divisions
1. Anterior pituitary or adenohypophysis
2. Posterior pituitary or neurohypophysis

8. HORMONES SECRETED BY ANTERIOR PITUITARY

9. HORMONES SECRETED BY POSTERIOR PITUITARY

10. GROWTH HORMONE OR SOMATOTROPIC HORMONE
• Secreted by somatotropes (acidophilic cells of anterior pituitary)
• Transported in blood by growth hormone binding protein.
• UQ
• Describe functions of growth hormone and its regulation.

11. GROWTH HORMONE FUNCTIONS OR ACTIONS
• Growth hormone is responsible for growth of almost all tissues of the body.
• On Protien Metabolism
1. Increases amino acids transport through cell membrane.
2. Increases RNA translation
3. Increases transcription of DNA to RNA
4. Decreasing catabolism of proteins
5. Promoting anabolism of proteins

12. GROWTH HORMONE FUNCTIONS OR ACTIONS
• On Fat Metabolism
• Mobilizes fat from adipose tissues (so fat concentration increases in body fluids).
• Increases free fatty acid concentration in liver.

13. GROWTH HORMONE FUNCTIONS OR ACTIONS
• On carbohydrates Metabolism
• Decrease in utilization of glucose for production of energy.
• Increase in glycogen deposition in cells
• Decrease in glucose uptake by cells
• Hyper secretion of growth hormone increases blood glucose levels enormously.

14. GROWTH HORMONE FUNCTIONS OR ACTIONS
• On Bones
• In embryonic stage growth hormone is responsible for development and differentiation of
bone cells.
• Synthesize and deposit proteins by chondrocytes and osteogenic cells.
• Make Calcium available for mineralization of bone matrix.

15. GROWTH HORMONE REGULATION
• Growth hormone secretion is STIMULATED by:
1. Hypoglycemia
2. Fasting
3. Starvation
4. Exercise
5. Stress and trauma
6. Initial stages of sleep
• Growth hormone secretion is INHIBITED by
1. Hyperglycemia
2. Increase in free fatty acids in blood
3. Later stages of sleep

16. ANTIDIURETIC HORMONE OR VASOPRESSIN (ADH)
• Secreted by supraoptic nucleus of hypothalamus.
• From here the hormone is transported to posterior pituitary by nerve fibers.
• Actions of ADH
Water Retention
1. Main function of ADH
2. Reabsorbs water from distal convoluted tubule and collecting duct in kidney.
Vasopressor action
1. Causes arteriolar vasoconstriction in all parts of body.
2. Due to vasoconstriction, blood pressure increases.

17. REGULATION OF ANTIDIURETIC HORMONE
• Stimulatory factors
1. Increased osmolality of extracellular fluid
2. Low blood volume and low blood pressure
3. Trauma, pain and anxiety
4. Drugs e.g. morphine, nicotine etc.
• Inhibitory factors
1. Decreased osmolarity of extracellular fluid
2. Increased blood volume and blood pressure
3. Alcohol

18. OXYTOCIN
• Secreted by paraventricular nucleus of hypothalamus.
• Secreted in both males and females.
• Transported from hypothalamus to posterior pituitary through nerve fibers
of hypothalamo-hypophyseal tract.

19. ACTIONS OF OXYTOCIN
Action on Uterus
In pregnancy, causes contraction of uterus and helps in expulsion of fetus.
In fertilization, facilitates sperm transport through female genital tract up to fallopian tube.
On milk ejection
Causes milk ejection from mammary glands.
On blood vessels
In large doses, causes vasodilation
On pituitary gland
Inhibits ADH secretion
On kidney
Causes water retention like ADH

20. REGULATION OF OXYTOCIN
• Stimulatory factors
1. Pregnancy
2. Lactation
3. Birth
• Inhibitory factors
1. Termination of pregnancy or abortion
2. Decrease in blood pressure
3. Stoppage of lactation