1. GROWTH HORMONE
Dr. Amel Eassawi

2. Objectives The student should be able to:
Identify the factors that affect growth beside the growth hormone.
Identify the hormones that affect growth beside the growth hormone.
Describe the metabolic effect of growth hormone.
Identify the relationship between growth hormone and insulin-like growth factors.
Explain the functions of the growth hormone.
Define the factors that influence the growth hormone secretion.
Describe the growth hormone abnormalities.
Describe the functions of melatonin hormone.
Explain the biological effect of melatonin hormone.

3. factors affect growth
Growth depends on growth hormone but is influenced by other factors as well:
Genetic determination of an individual’s maximum growth capacity.
An adequate diet.
Freedom from chronic disease and stressful environmental conditions.
Normal levels of growth-influencing hormones

4. Hormones regulating growth
Thyroid Hormone
Insulin: Stimulates IGF-1 (Somatomedin)
Prolactin: Stimulates IGF-1
Testosterone
Estrogen

5. Hormones regulating growth
Other hormones besides growth hormone are essential for normal growth
Thyroid hormone
Growth severely stunted in hypothyroid children
Hypersecretion does not cause excessive growth
Insulin
Deficiency often blocks growth
Hyperinsulinism often stimulate excessive growth
Androgens
Play role in pubertal growth surge, stimulate protein synthesis in many organs
Estrogens
Effects of estrogen on growth prior to bone maturation are not well understood.

6. Growth RATE Not continuous
Factors responsible for promoting growth are not the same throughout growth period
Fetal growth
Promoted largely by hormones from placenta
GH plays no role in fetal development
Postnatal growth spurt
Displayed during first two years of life
Pubertal growth spurt
Occurs during adolescence

7. Growth Hormone

8. Growth Hormone Functions
Direct Effect
Growth hormone binds directly to its target cells:
bones & muscles
Stimulates growth
Hypertrophy: increase in size/volume of cells
Example: increase in bone thickness
Stimulates cell reproduction
Increased rate of mitosis
Hyperplasia: increase in the number of cells, proliferation rate
Example: increase in bone length
Stimulates cell metabolism
Increase protein synthesis
Increase fat breakdown for energy
Increase glycogen breakdown so that there is an increase in blood glucose levels to fuel cell growth

9. Bone growth at the epiphyseal plate

10. Growth Hormone Functions
Indirect Effect
Most growth occurs through the indirect method.
GH acts as a tropic hormone.
stimulating liver’s production of somatomedins
Primary somatomedin is insulin-like growth factor (IGF-1)
Acts directly on bone and soft tissues to bring about most growth-promoting actions
Stimulates protein synthesis, cell division, and lengthening and thickening of bones

11. Growth Hormone Regulation
hypothalamus
growth hormone releasing hormone (GHRH)
growth hormone inhibiting hormone Somatostatin (GHIH)
anterior pituitary
growth hormone (GH)
liver
Insulin-like growth factor 1 (IGF-1)
GH half-life is 20 – 30 min

13. GROWTH HORMONE Secretion
Secreted in bursts (not continuous)
GH released mostly during sleep
optimal at night time
Changing sleeping pattern affects GH release
GH production declines with age
Increased Growth Hormone Secretion:
Exercise regularly
8 hours of sleep
Protein-rich diet
Avoid Stress

14. GH Associated Disorders
Dwarfism
Gigantism
Acromegaly

15. Dwarfism Deficiency in GH Short stature Adult 4'10" or shorter
Proportional body
Affects 1/10 000
Occurs in children
GH absent during child’s development

16. Gigantism Excessive growth and height Continuous secretion of GH
Open epiphyseal plate
Affects bone growth length
Occurs during childhood

17. Robert Wadlow the world’s Tallest Man
( )
8 feet 11 inches and 439 pounds when he died

18. Tallest person alive Sultan Kosen born in Turkey 8 feet 1 inch

19. Comparing Growths

20. Gigantism Pituitary Adenoma Average brain size
Tumour formed by pituitary gland
Secretes excessive GH / IGF-1
Non cancerous
Average brain size
Skull grows but brain size stays the same, thus the brain function is unchanged

21. Gigantism Problems Poor blood flow due to large body
Increased muscle mass but weaker muscle
Excess GH produces salt in muscle tissues
Muscles swell with water
Results in disproportional muscle growth  weaker muscles

22. Acromegaly Increased GH secretion in adults Closed epiphyseal plate
Bone lengthening stopped
Bone width increases
Slow progression
Effect of Acromegaly:
Soft tissue harden
Deeper voice because larynx enlarges
Bigger tongue and lips that affects breathing
Cartilage in nose enlarges making nose broader

23. Acromegaly: Physical Effects
Bone thickens
Forehead expands
Eyebrow ridges bulge outwards
Cheekbones more prominent
Mandible enlarges and pushes lower teeth outwards and become widely space

24. Acromegaly: Effect on Muscles
Impaired Movements
Enlargement of bones crushes peroneal nerve in knee
Nerve carries messages to move foot and lower leg
Nerve cannot send messages to leg to trigger walking motion
Also cause muscle numbness
Leads to early death

25. Acromegaly: Heart Defects
Heart tissue stiffen
heart cannot contract and relax
Ventricle harder to fill up
Heart grows bigger in order to pump out sufficient blood

26. Acromegaly: Lung Defect
As bones grow, rib cage expands
Diaphragm is stretched thin and loses elasticity
Breathing is reduced

27. Pineal Gland
The pineal gland is a small, cone – shaped structure located in the center of the brain, diencephalon.
The pineal gland is composed of pinealocytes and glial cells.
Connects endocrine with nervous system

28. Pineal Gland Functions: Secretion of the Hormone Melatonin
Regulation of Endocrine Functions
Conversion of Nervous System Signals to Endocrine Signals
Causes Feeling of Sleepiness
Influences Sexual Development
Precursor of melatonin is serotonin.
Synthesis and secretion of melatonin is affected by light exposure to the eyes.

29. Biological Effects of Melatonin
Helps keep body’s circadian rhythms in synchrony with light-dark cycle
Effects on Reproductive Function
Anti-gonadotropic
Effects on Sleep and Activity
Acts as antioxidant to remove free radicals
Alterations in melanin pigment distribution

30. References Human physiology, Lauralee Sherwood, seventh edition.
Text book physiology by Guyton &Hall,11th edition.
Physiology by Berne and Levy, sixth edition.