1

GROWTH HORMONE
&
GROWTH CURVE

2 Dr. Ismoth Ara Jerin

Resident
MD (Phase-A) Part-I
Department of Physiology
BSMMU
OVERVIEW

 Introduction to GH
 Chemistry & Biosynthesis

 Mechanism of action

 Metabolic effects of GH

 Factors affecting GH secretion

 Growth curve

 Abnormalities of GH secretion

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 INTRODUCTION TO GH

•Also called somatotropic hormone

or somatotropin.

•GH causes growth of all tissues of the

body that are capable of growing .
Fig: Pituitary gland
in Sella turcica.

•Secreted from anterior pituitary.

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(Tortora 2012)
Fig: Hypothalamic-hypophysial portal system
5

(Hall 2012)
 Cells of anterior
Pituitary:
1. Somatotropes-(30-
40)%
2. Corticotropes-20%

3. Thyrotropes-(3-5)%

4. Gonadotropes-(3-5)%

5. Lactotropes-(3-5)%

Fig:- Cellular structure

of anterior pituitary
6

(Hall 2012)
 CHEMISTRY & BIOSYNTHESIS

 Chemically GH is protein in nature.

 Single chain of 191 amino acids.

 M.W -22005

 Long arm of human chromosome

17contains the growth hormone-hCS
Cluster that contains 5 gene- Fig:- Structure of GH
one hGH-N
one hGH-V
Two hCS
one hCS pseudogene
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(Barrett et al. 2012)
SYNTHESIS OF GH

(Boron & Boulpaep 2012)

 Normal concentration of GH in plasma:
✓ In adult- 1.6-3ng/ml
✓ In child / adolescent- 6ng/ml

 Half life:-6-20 min

 Daily secretion of GH- 0.2-1mg/d in adults

 Metabolism- rapidly metabolized in liver.

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Fig: Insulin & IGF-1 receptors Fig: GH receptor
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(Boron & Boulpaep 2012)

MECHANISM OF ACTION OF GROWTH
HORMONE:

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(Barrett et al. 2012)
METABOLIC EFFECT OF GH :
On protein metabolism:
1. ↑ the transport of AA through the cell
membrane.

2. ↑ the RNA translation to cause protein

synthesis by ribosome.

3. ↑ nuclear transcription of DNA to form RNA.

4. ↓ catabolism of protein and amino acid.

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On fat metabolism:

 ↑ Mobilization of fat from adipose tissue.

 ↑ Free fatty acid level in blood.

 ↑ Utilization of fatty acid for energy.

On carbohydrate metabolism:

 ↓ Glucose uptake in tissues (e.g skeletal muscle

& adipose tissue).
 ↑Glucose output by liver.

 ↑ Insulin secretion but resistant to insulin action. 13

On electrolytes:

 ↑ GI absorption of Ca++.

 ↓ Na+ & K+ excretion (independent of adrenal

gland action) .

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On bones:-
 ↑ Bone protein deposition by osteogenic &
chondrocytic cells.
 ↑ Rate of cell multiplication.

 Conversion of chohdrocytes to osteogenic

cells.
 Thus, results in deposition of new bones.

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 SOMATOMEDINS
 Also called IGF.

 At least 4 Somatomedins have been

identified.

 Most important one is Somatomedin C /IGF-1

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(Barrett et al. 2012)

SOMATOMEDIN C
 Secreted by Liver, Cartilage & other tissues
 M.W-7500
 Plasma level-10-700ng/ml; peaks at puberty.
 Half life- 20 hrs.

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Fig: Serum IGF-1 & rate of height increase .
(Boron & Boulpaep 2012)
 Somatomedins have potent direct effect on all
aspects of bone growth.

Fig: Direct & indirect effect of growth hormone 18

(Barrett et al. 2012)

METABOLIC EFFECT OF EXCESSIVE GH

 Ketogenic effect:
Excessive GH

Mobilization of fat in large amount

from adipose tissue

Excessive amount of acetoacetic acid formed

by liver & released into body fluids

Ketosis 19
 Diabetogenic effect:

Excess GH causes ↑ FA
concentration in blood above normal

↓sensitivity of liver & skeletal muscle to insulin

Results in insulin resistance

Decrease glucose uptake in tissues

Increase glucose production by liver

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 Increased blood glucose concentration

Compensatory increase in insulin secretion

β-cell burn out

Diabetogenic effect of GH

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HYPOTHALAMIC CONTROL OF GH SECRETION

Fig: Feedback control

of GH secretion

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(Barrett et al. 2012)

 GHRH

Combines with receptor on the outer surface of somatotropes

Activation of adenylyl cyclase system

↑ intracellular cAMP level

Short-term effect Long-term effect

↑ Ca++ transport into the cell ↑ transcription in nucleus

Fusion of GH secretory vesicle Stimulates the synthesis

with cell membrane of new GH
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Release of GH into blood
FACTORS AFFECTING GH SECRETION

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(Hall 2012)
Fig: Typical variations in GH secretion throughout the day

25

(Hall 2012)
Fig: Effect of extreme
protein deficiency on
plasma concentration
of GH in Kwashiorkor

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(Hall 2012)
Plasma concentration of GH in different age:

27

(Hall 2012)
GROWTH PERIOD:

28
(Barrett et al. 2012)
GROWTH CURVE

29
(Barrett et al. 2012)
ABNORMALITIES OF GH SECRETION

 Panhypopituitarism:
This term means decreased secretion of
all the anterior pituitary hormones.

It may be –
a) Congenital.

b) Sudden onset at any time during life.

❖ Most often it results from pituitary tumour that

destroys the pituitary gland.
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 Dwarfism:

✓ Mostly due to panhypopituitarism during

childhood.

✓ Physical parts of the body develop in appropriate

proportion but the rate of development is greatly
decreased.

✓ The person dosen’t pass through puberty due to

lack of gonadotropic hormone.

✓ 1/3rd case- GH is deficient only & person mature

sexually. 31
Fig: Normal & abnormal growth 32

(Barrett et al. 2012)

 Le‫׳‬vi-Lorain Dwarf & African pygmy:

✓ GH level –Normal / high

✓ Hereditiary inability to form Somatomedin C.

Fig: African pygmy 33

(www.pygmies.org)
 Panhypopituitarism in adult:

It results from:-
1. Craniopharyngioma

2. Chromophobe tumours

3. Thrombosis of pituitary blood

vessels.

Patient is –

•Lethargic
•Gaining weight
•Sexual function is lost 34
 Treatment with GH:

✓ GH is produced in E.coli by recombinant DNA

technology & available for treatment purpose.

Fig : E.coli

✓Dwarfs with pure GH deficiency can be 35

completely cured if treated early in life.
(www.studentconsult.com)
EFFECTS OF HYPER SECRETION OF GH
 Gigantism:
• Excess secretion of GH before the
epiphyseal closure.

• Cause-Acidophilic tumour in
anterior pituitary.

• Clinical feature-
▪ Abnormal height- upto 8 feet.
▪ Hyperglycemia.
▪ Full blown DM- in 10% case

• Eventually Panhypopituitarism
develop due to destruction of 36
pituitary gland by tumour.
(Sherwood 2012)
 Acromegaly:

• Occurs due to excesses secretion of GH in adults

after epiphyseal closure.

• The person cannot grow taller, but the bones become

thicker & soft tissue can continue to grow.

• Cause-Acidophilic tumour in anterior pituitary.

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 Clinical feature:

• Enlargement of hands & feets.

• Potrusion of lower jaw.
• Bosses on the forehead.
• Enlargement of supraorbital
ridge, portion of vertebrae.
• Kyphosis.
• Enlarged tongue & liver.
• Kidney become greatly
enlarged. Fig:Acromegalic patient

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(Hall 2012)
 39

(www.studentconsult.com)
BIBLIOGRAPHY
Books:
1. Guyton A C, Hall J E, Text book of medical Physiology,12th edition, India,
Elsevier,2012.

2. Barret K E, Barman S M, Boitano S ,Brooks H L,Ganong’s review of

medical Physiology,24th edition, India, McGraw-Hill,2012.

3. Tortora G.J, Derrickson B,Principles of Anatomy & Physiolgy, 13th ed,

USA, John Wiley & sons,2012.

4. Sherwood lauralee, Fundamentals of human physiology,4th edition,

Brooks/Cole,2012,Canada.

5. Boron W.F, Boulpaep E.L, Medical Physiology, 2nd ed, USA, Elsevier, 2012.

Website:

1. www.studentconsult.com 40
2. www.pygmies.org
ACKNOWLEDGEMENT

-Respected teachers

- Seniors

- Colleagues

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THANK

YOU

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