This document discusses the physiology of growth and development from conception through adulthood. It defines the key stages of development, describes common growth curves, and lists the major factors that influence growth, including genetics, nutrition, hormones, and the environment. In particular, it focuses on the roles of growth hormone, IGF-1, thyroid hormones, sex hormones, insulin, and cortisol in stimulating or inhibiting growth and development at different life stages.

1. PHYSIOLOGY OF GROWTH & DEVELOPMENT
Dr Hrushikesh S

2. CONTENTS
1) Introduction- Definitions, differences and its need.
2) Scientific contribution.
3) Comparative physiology.
4) Growth physiology- principles, growth curve, factors affecting growth.
5) Growth Hormone & Somatomedins.
6) Applied Physiology.
7) Did you know?
8) References.

3. Growth and developmental age periods.
1) Zygote-- very 1st stage of life formed after fertilization (union of egg
and sperm).
2) Embryo-- First 8 weeks after fertilization.
3) Fetus-- 8th week till birth.
4) Neonate--From birth till 1 month.
5) Infant– From 2nd month to 1 year.
6) Toddler-- 1 year to 3 years.
7) Preschool – 3 years to 6 years.
8) Middle childhood -- 6 to 12 years.
9) Late childhood or Adolescence --13to 18 years.

4. Growth
• Defined by scientists like Todd, Huxley ,Meridith etc

5. Development
• Defined by scientists like Todd, Hurlock, J.E.Anderson etc

6. DIFFERENCE
GROWTH
Physical sense
Changes in quantitative
aspects
Does not continue
throughout the life. Stops
when maturity attained
DEVELOPMENT
Change in shape, form
resulting in improved
function
Changes in qualitative
aspects
Continues throughout the
life and is progressive.

7. THE HUMAN LIFE
• Starts from a single cell
• ZYGOTE EMBRYO FOETUS CHILD ADULT
BIRTH

8. WHY ?
• Growth and development is seen
in the living organisms.

9. Optimum function

10. Optimum function
Existence

11. The difference between a child and an adult
 Size
 Matured functions

12. Noble prize in Physiology & Medicine- 1986
Stanley Cohen Rita Levi - Montalcini
For their
contribution in
discoveries of
growth factors

13. COMPARATIVE PHYSIOLOGY

14. Developmental period
12 days
64 days
67-69
days
660 days

15. HUMAN GROWTH
• Not uniform throughout the life as seen in rat which is slow and
progressive.
• Complex phenomenon involving integrated development of
• Physical
• Mental
• Immunological
• Reproductive process

22. GROWTH OF
A PERSON
TISSUE
GROWTH
Hyperplasia Hypertrophy
TISSUE GROWTH
DIFFERENTIATION
Brings about
functional
maturation i.e.
DEVELOPMENT
Which brings about physical
growth
Different
growth patterns
are observed in
human

23. Pattern of growth during fetal life

24. Pattern of Growth & Development during
childhood and adolescence
Scammon’s growth curve
Types of tissue growth patterns
1. PHYSICAL / GENERAL
2. NEURAL
3. LYMPHOID
4. REPRODUCTIVE

25. SCAMMON’S GROWTH CURVE
Types of growth patterns
1. PHYSICAL / GENERAL
2. NEURAL
3. LYMPHOID
4. REPRODUCTIVE

26. SCAMMON’S GROWTH CURVE
Types of growth patterns
1. PHYSICAL / GENERAL

27. SCAMMON’S GROWTH CURVE
Types of growth patterns
1. PHYSICAL / GENERAL
2. NEURAL

28. SCAMMON’S GROWTH CURVE
Types of growth patterns
1. PHYSICAL / GENERAL
2. NEURAL
3. LYMPHOID

29. SCAMMON’S GROWTH CURVE
Types of growth patterns
1. PHYSICAL / GENERAL
2. NEURAL
3. LYMPHOID
4. REPRODUCTIVE

30. I GENERAL GROWTH CURVE
4 DISTINCT PHASES
• A RAPID INCREASE GROWTH
• A SLOW PROGRESSIVE GROWTH
• SECOND RAPID GROWTH
• SLOW GROWTH AFTER PUBERTY

31. RAPID INCREASE GROWTH PHASE
• Occurs during infancy (Birth-3yrs)
• Infantile growth spurt.
• This rapid growth is characterised by-
 Increase in birth weight to
• 2 times by 6th months of age.
• 3 times by 1 year of age.
• 4 times by 2 years of age.
 Increase in height by 2cm-2.5cm per
month in the 1st year of postnatal life.
• Weight increases from 3kg to 12kg.
• 30% of the adult growth.

32. SLOW PROGRESSIVE GROWTH
• Takes place from 3 to 10 years of
age.
• Boys are slightly taller than girls.
• By the end of 10 years ,
60% of adult growth is achieved.

33. SECOND RAPID GROWTH
• Seen at 10-16 years.
• Pubertal growth spurt.
• Weight gain is about 3.5kgs/year between 12-16
years of age & height by 4-7cms/year.
• Average age for pubertal growth in
• Girls is 12-14 years.
• Boys is 14-16 years.
• It is due to secretion of-
• Sex hormones
• Growth hormone
• IGF-I
• Increase in weight in girls --- due to fat deposition.
in boys---due to muscular growth.

34. SLOW GROWTH
• Is seen after puberty (16-20 yrs)
• This continues up to 20 years of
age.
• Thus we saw two growth spurts-
I. At infancy.
II. At puberty.

35. II NEURAL GROWTH
• Shows growth of brain, spinal cord and visual apparatus.
• grow rapidly after birth.
• At the end of 1st yr. of postnatal life brain growth is 60%.
• At the end of 2nd yr. brain growth is 80%.
• At the end of 5th yr. brain growth is almost 100% of adult.
• Head circumference is important up to 3-5 years of age.
• Numbers of neurons are not increased.
• Increased in size of neurons, dendrite branching and number of
synapses.
• Early age malnutrition can affects the growth of
brain.

36. III LYMPHOID GROWTH
• Lymphoid organs –tonsils, adenoid, thymus, spleen, lymph
nodes and lymphoid tissue of intestine
• Show rapid growth during infancy and childhood. Why?
• Reaches maximum by 10-12 years and declines after that.

37. IV REPRODUCTIVE GROWTH
• Reproductive organs – gonads and accessary reproductive organs.
• Remain dormant in childhood.
• Grow at rapid rate around puberty.
• This rapid growth is due to secretion of GONADOTROPHINS.
• Gonadal growth pattern is opposite to that of neural growth pattern.
• A different type of growth is shown by
• Adrenal Glands &
• Uterus
They are relatively large at birth, then they lose weight rapidly and regain
their birth weight just before puberty.

38. Factors affecting Growth & Development
Adequate & Favorable
factors
OPTIMUM GROWTH

39. 1. GENETIC FACTOR
• Most important deciding factor of growth.
• Up to certain extend , gene expression decides the
height.
• Children of tall and heavy parents are likely to
have the same stature.
• Some races are taller in comparison to others.
• Difference between male and female growth
pattern, adolescent spurt appear to be genetically
controlled via the hypothalamus.

40. 2. NUTRITIONAL FACTOR
• For optimum growth , balanced diet is necessary.
• Balanced diet must be adequate not only in calories but also in proteins,
carbohydrates, fats, vitamins, minerals.
• Their requirements are increased during active periods of growth.
• Undernutrition and malnutrition in childhood is responsible for stunting of
growth.
• If lack of nutrition is prolonged severe- stunting occurs which may be
irreversible.
• If lack of nutrition is less severe & for short period- stunting may be
reversible by restoring normal diet leading to compensatory increase in
rate of growth. This is called as catch up growth.
• The mechanisms for catch up growth are unknown, but recent evidence
suggests that it may be related to the rate of stem cell differentiation
within the growth plates.

41. • Undernutrition affects the growth of different organs and tissue
unevenly-
• Dietary deprivation affects muscles and fat more than bone.
• Skeletal maturation is less affected than skeletal growth.
• Total brain growth is inhibited more than myelination.
• At puberty malnutrition affects the genitals less commonly than other
organs.
Hence Japanese born & bred in US. are taller than their compatriots in
Japan.

42. 3.Environmental Factors
• They comprise of the Intrauterine (prenatal factors) for a fetus and
the postnatal factors for the new born.
PRENATAL

44. METABOLIC GROWTH
• Growth is the balance between anabolism
and catabolism.
• Growth is due to anabolism for which the
energy is driven from catabolism.
• Protein anabolism is favoured by –
• Growth hormone
• Thyroid hormone
• Insulin
• Catabolism is favoured by –
• Glucocorticoids secreted by adrenal cortex

45. 4. HORMONAL FACTOR
HARMONES ACTIONS
GROWTH
HORMONE
Major stimulus of postnatal growth: Induces precursor cells to differentiate and secrete
insulin-like growth factor 1 (IGF-1), which stimulates cell division. Stimulates liver to secrete IGF-1.
Stimulates protein synthesis.
INSULIN Stimulates fetal growth
Stimulates postnatal growth by stimulating secretion of IGF-1.
Stimulates protein synthesis.
THYROID
H0RMONES
Permissive for growth hormone’s secretion and actions. Permissive for development of the central
nervous system.
SEX
HORMONES
Testosterone -- Stimulates growth at puberty, in large part by stimulating the secretion of growth
hormone. Causes eventual epiphyseal closure. Stimulates protein synthesis in male.
Estrogen --Stimulates the secretion of growth hormone at puberty. Causes eventual epiphyseal
closure.
CORTISOL Inhibits growth
Stimulates protein catabolism

46. HORMONAL FACTOR
• Growth Hormone
• Thyroid Hormone
• Gonadotrophins

47. GROWTH HORMONE
Secretion --By anterior pituitary somatotrophic cells
Chemical structure-- Polypeptide ( Mr22 kDa).
Rate of secretion-- around 1-2 mg per day and pulsatile in nature.
Action of GH on its receptor -- GH binds to a cell surface receptor ->
dimerisation of 2 GH receptors -> forms a dimeric complex -> activates
tyrosine kinase & protein kinase on tyrosine residues. This also causes
phosphorylation of the receptor.
Importance: Determines the height of an individual during childhood by
promoting the linear growth in the skeleton. Also increases size of muscles,
connective tissues, viscera by promoting hyperplasia and hypertrophy of
cells.

48. GROWTH HORMONE
Physiological effects of
GH on growth
Metabolic effect
Protein metabolism
Increases protein
synthesis and
decreases protein
utilization
Fat metabolism
Enhances fat
utilization & ketogenic
Carbohydrate
metabolism
Increases glucose
level & increases
insulin resistance
Trophic effect
Cartilage & Bone /
Muscle, organ

49. •Trophic effects ( growth promoting effects)
Direct : 1) Effects on bones & joints:
a)Direct stimulatory effect on chondrocytes thus ↑ the rate of
differentiation & hence promoting cartilage formation.
b)Elongation of the shaft of long bones.
c) ↑ thickness of the bone by deposition of a layer of osteoblasts.
2) Growth & Repair– Enhanced by GH as it increases the uptake of Amino
acids & increases the rate of protein synthesis.
Indirect: The indirect action of GH is mediated by a family of peptide
hormones called Insulin like growth factors formerly known as
somatomedins.

50. Somatomedins
Somatomedin- C are not required during foetal growth.
Somatomedin- A is required for foetal growth, its secretion is largely
independent of GH.
In fetus when IGF-II is overexpressed, the growth of organs is
disproportionate.
GH
LIVER
TISSUES
SOMATOMEDINS GROWTH
Somatomedin- A ( IGF- II )
Somatomedin- B
Somatomedin- C ( IGF- I )

51. • IGF- I concentration in the plasma
closely follows the rate of growth
hormone secretion.
• Spikes of GH secretion are larger
during puberty.
• Half life of GH in plasma = 20 min.
where as Somatomedin C = 20 hrs.
IGFBP-3 accounting for 95%
of the binding in circulation.

52. • Are Somatomedins responsible for all effects of GH ? NO
Metabolic effects of GH are independent of IGF-I.
• GH plus IGF-I(circulating & locally formed) are required for the proper
growth.
• Growth Factors-
i. Epidermal growth factor.
ii. Platelet derived growth factor.
iii. Fibroblast growth factor.
iv. Nerve growth factor.
v. Ovarian growth factor.

54. FACTORS AFFECTING GH SECRETION
Stimulatory
1. Deficiency of energy substrate
i. Hypoglycaemia
ii. 2-deoxyglucose
iii. Exercise
iv. Fasting
2. Protein meal, Arginine a.a.
3. Glucagon, Ghrelin
4. Stress
5. Deep sleep
6. L-Dopa
7. Oestrogens & Androgens
Inhibitory
1. REM sleep
2. Glucose
3. Cortisol
4. FFA
5. Obesity
6. Aging
7. Medroxyprogesterone
8. GH ( exogenous )
9. IGF-I
10. Somatostatin

56. APPLIED
HYPOSECRETION
Dwarfism
• GH deficient dwarfs – Have low GH levels and responds to exogenous GH.
• IGF-I deficiency– eg. African pygmies have normal plasma GH levels but GH
binding protein is moderately reduced. Plasma IGF-I concentration fails to
increase at puberty.
• Levi-Laron dwarfism- High GH but low IGF-1 and IGF-2; lack functional
hepatic GH receptor.
HYPERSECRETION
• Gigantism – Excess of GH before epiphyseal closure.
• Acromegaly – Excess of GH after epiphyseal closure.

57. All have
stunted but
proportionate
growth.

58. • Achondroplasia -
• Most common form of Dwarfism
showing disproportionate growth.
• Inherited as autosomal
dominance ( Mendelian ).
• Failure of growth of long bones.
• Mutation in gene that codes for
Fibroblast Growth Factor
receptor-3 ( FGF-3 )

61. THYROID HORMONES
• They are permissive to GH.
• They are required during intrauterine life as well as after birth.
• Stimulate growth by- Direct effect on metabolism.
- Indirectly by GH & IGFs.
• Required for tissue differentiation & maturation.
• Stimulate branching of dendrites, myelination and increase nos. of
synapses.
Applied- Hypothyroidism in infant leads to dwarfism called as
Cretinism having infantile features.

63. ANDROGENS & OESTROGENS
• Responsible for growth spurt at puberty.
• Stimulate secretion of GH & IGF-I.
• Testosterone is more anabolic, results more pubertal growth in male.
• Weight in - male = muscular mass Testosterone
- Female = fat deposition Oestrogen
• Oestrogen is more potent than testosterone for having action on
epiphyseal growth plate.
• It first stimulate the epiphyseal growth plate and secondly leads to
fusion of epiphysis to the shaft.
Applied- Patient with precocious puberty have short stature.

64. GLUCOCORTICOIDS
• Permissive role on GH
• Physiological doses are required for growth.
• Doses excess than normal doses inhibit growth, inhibition takes place at
tissue level.
Applied – Such situation may arise pathologically eg. Cushing's disease, the
rate of skeletal maturity is increased so the potential for further growth is
reduced.
INSULIN
• Stimulates the growth.
• Diabetic children do not grow.
• Carbohydrates +Proteins + Insulin= Growth

65. Vitamin D metabolites & parathyroid
hormones
• These stimulate the intestinal uptake of calcium . Also have a direct
effect on mineralization of bones.
• Applied: Rickets in Children.
Osteomalacia in Adults.

67. Did you know
 Anamoly scan -- Done at 18th week of pregnancy can accurately diagnose
even the slightest of the growth defects.
 1958 GH tragedy.
 FDA has approved the use of rHGH for diseases like severe wasting, IUGR etc
but the most common use of GH is not in diseases but in sports, in form of
abuse specially in body building competitions like Mr Olympia where doping
is legal.
 GH is species specific ie isolation of GH from 1 species & its administration
into another species will not have any beneficial growth related effects in
them.
 Arginine and glutamine form the most part of the PRE work out ( exercise)
drinks as they are believed to increase more of GH levels during exercise.
 Levi-Laron dwarfs are immune to cancer and diabetes.

68. REFERENCES