1. GROWTH HORMONE
Dr. Shaikh Mujeeb Ahmed

2. Objectives Factors influence growth beside growth hormone
Metabolic effect of GH
Relation between GH & insulin-like growth factors
Functions of GH
Factors influencing GH secretion
GH abnormalities
Hormones affecting growth beside GH

3. Endocrine Control of 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
Prolactin: Stimulates IGF-1
Testosterone
Estrogen

5. 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 spurs excessive growth
Androgens
Play role in pubertal growth spurt, stimulate protein synthesis in many organs
Effects depend on presence of GH
Estrogens
Effects of estrogen on growth prior to bone maturation are not well understood poorly

6. Growth Stages - Regulation
Prenatal – Maternal factors, Fetal Insulin, & IGF
Growth in infancy – Genetic factors, GH production, Thyroid hormone, IGF
Adolescence- GH, Insulin, IGF & Sex hormone surge

7. Growth hormone (GH) A peptide hormone (~200 amino acids)
Also known as somatotropin:
tropic hormone that affects somatic cells

8. Growth Hormone

9. GH Function: Direct Effect
GH 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

10. Bone growth at the epiphyseal plate

11. GH function on metabolism
Stimulates cell metabolism
Increase protein synthesis
amino acid transport through cell membrane
 catabolism of protein
Increase fat breakdown for energy
Carbohydrate metabolism
 use of glucose for energy
 glycogen deposition in the cell
 blood glucose levels
 insulin secretion

12. GH Function: Indirect Effect
Most growth occurs through the indirect method
GH acts as a tropic hormone
Signals the liver to produce Insulin-like Growth Factors (IGF)

13. Growth Regulation: Neuroendocrine pathway
Location
Hormone
Hypothalamus
Growth hormone release hormone (GHRH)
Growth hormone inhibiting hormone (GHIH) aka somatostatin (SS)
Anterior Pituitary
Growth hormone (GH)
Liver & other tissues
Insulin-like growth factor (IGF)

14. IGF-1: Insulin-like Growth Factor 1
targets almost every cell in the body including the muscle, cartilage, bone, and skin cells
Stimulates hypertrophy and hyperplasia of the cells

15. 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

16. Negative Feedback High levels of IGF-1 High levels of GH
Stimulates GHIH/SS
decreased secretion of GH
High levels of GH
inhibits GHRH

17. GH Secretion Secreted in bursts (not continuous)
GH his released most during sleep
optimal at night time
Changing sleeping pattern affects GH release
GH production declines with age

18. Increasing GH Production
Exercise regularly
8 hours of sleep
Protein-rich diet
Avoid Stress

19. GH Associated Disorders
Dwarfism
Gigantism
Acromegaly

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

21. Gigantism – Vertical Growth
Excessive growth and height
Continuous secretion of GH
Open epiphyseal plate
Affects bone growth length
Occurs during childhood

22. World’s Tallest Man: Robert Wadlow (1918-1940)
8 feet 11 inches and 439 pounds when he died

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

24. Gigantism Cause 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

25. 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

26. Comparing Growths

27. Acromegaly – Lateral Growth
Increased GH secretion in adults
Closed epiphyseal plate
Bone lengthening stopped
Bone width increases
Slow progression

28. 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

29. Acromegaly: Physical Effects
Soft tissue harden
Deeper voice because larynx enlarges
Bigger tongue and lips that affects breathing
Cartilage in nose enlarges making nose broader

30. 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

31. 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

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

33. The 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 & glial cells.
Connects endocrine with nervous system

34. 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

35. Precursor of melatonin is serotonin.
Synthesis and secretion of melatonin is affected by light exposure to the eyes.

36. 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