Endocrinology

1. K.G. ART’S & SCIENCE COLLEGE RAIGARH (C.G.)
Session - 2019-20
Deparment of Zoology & Research Center
Subject :- General and Comparative Endocrinology.
Seminar Topic:- Insulin Family (IGF-I & IGF-II) .
Guided by Submitted by
Proff. Ranjana Sahu mam . Girja Prasad Patel
M.Sc. I Sem. Zoology

2. INSULIN FAMILY (IGF-I & IGF-II)
SYNOPSIS :-
1. Growth Hormone.
2. Introduction.
3. IGF Sources.
4. IGF-I (Insulin like growth factor-I).
5. IGF-II (Insulin like growth factor-II).
6. Bio-synthesis of IGF-I & IGF-II.
7. Mechanism of Action.
8. Conclusion.
9. Reference.

3. 1. GROWTH HORMONE :-
Although Pituitary growth hormones(GH)
is clearly associated with growth, most of its action are mediated
indirectly through peptide hormones the somatomedins.
Beside the important action of Insulin
on carbohydrates and fat metabolism, this hormones also plays an
important role in growth regulation.
Certain steroid hormones particularly androgens
play crucial role in normal growth processes. Other hormone such as the
glucocorticoid and the thyroid hormones are essential (Permissive) for the
growth promoting activities of the peptide growth hormones.

4. 2.INTRODUCTION :-
IGF means insulin like growth factor. It is a
growth factor that is similar as insulin. Insulin binds will the growth factor
that contain disulfide bond and form IGF. IGF-I & IGF-II is a responsible for
growth. IGF-I & IGF-II are bind to IGFR and work autocrine and paracrine
manner.
3. IGF SOURCES :-
IGF is synthesis and by Liver.
Liver IGF production stimulate by GH.

5. 4. IGF-I (Insulin like growth factor-I) :-
• Insulin like growth factor-I (IGF-I) is also called somatomedin ‘C’.
• Human IGF-I is encoded by the IGF-I gene.
• Reffered as “Sulfation factor”(sulphate present in the term of disulfide
bond) and term as non suppresible insulin like activity.
• Structure :- consist of 70amino acid, single chain, 3 disulfide bond
present.
• Molecular weight – 7649 Dolton’s.
• Receptor known as IGF-IR or IGFR.
• Regulate work as autocrine and paracrine.
• Important in childhood growth and continue into anabolic effect in
adult.

6. • IGF-I is a member of a family of growth factor which are structurally
closely related to pro-insulin the similarity is so great that IGF-I can bind
to and activate insulin receptors.
• If growth hormone insensitive, lack of hormone receptor or failure or
the downstream signalling pathway.
• Single binding protein – IGFBP-1 (Regulation in insulin.)…IGFBP-3
(Major binding protein 80%)…….IGFBP-7.
• High rates production during IGF-I “Pubertal growth spurt” but lowest
level at during old.
• Protein intakes increases IGF-I level independent of calorie
consumptions.
• Decreasing by insulin level fluctuation or changes in genetic make-up.
• IGF-I is produced primorily by the “liver” as endocrine hormone as well
as in target tissue in a paracrine /autocrine fushion.

8. 5. IGF-II (Insulin like growth factor-II) :-
• Insulin like growth factor-II also known as IGF-II, Somatomedin “A”.
• Very much resemble to IGF-I.
• IGF-II binds with own receptor IGF-IIR or binds to IGF-IR (Depends on
Secretion of IGF-II, low Secretion binds to IGF-IR and Normal Secretion
binds to IGF-IIR.)
• IGF-II work autocrine and paracrine manner.
• Structure :- IGF-II is one of the three protein hormone that structural
similar to insulin.
• IGF-II consist of 67 amino acid have sequence nomology of 62 %.
• Im human, the IGF-II gene is located on chromosome -11p.
• It has growth regulation, insulin like and Mitogenic activity.

10. • IGF-II secretes by the “liver” and to circulate in the blood.
• Function :-
- Major role of IGF-II is as a growth promoting hormone during
‘Gastation’.
- In the process folliculogenesis.
- Co-hormone together with both FSH & LH.
- Induced by Placental lactogen during prenatal development.

11. 6. Bio-synthesis of IGF-I & IGF-II :-

13. - IGF-I is a primary mediater of the effects of growth hormone (GH).
Growth is made in the anterior pituitary gland is released into the blood
stream and then stimulates the liver to produce IGF-I and IGF-II.
- IGF-I / IGF-II then stimulates systemic body growth and has growth
promoting effects on almost every cell in the body.
- Especially skeletal muscle, cartilage, bone, liver, kidney, nerve, skin,
and lungs cells. In addition to the insulin like effects. IGF-I can also
regulate cellular DNA synthesis.

14. 7. Mechanism of Action :-

16. • IGF-I /IGF-II binds to at least two cell surface receptor tyrosine kinase.
• Binding to the IGF-IR receptor initiates intracellular signalling.
• Binding of IGF-I to receptor includes dimerization.
• Receptor undergoes auto and cross phospgorylation.
• IRS-I having SH2 domain interact with the phosphorylated by receptor.
• On the inner side IRS-I is interact with GRB-2.
• GRB-2 activate RAS protein by interacting with SOS.
• RAS protein interact with the N-terminal and RAF kinase leading to the
activation of MAP kinase pathway.
• Phosphorylated and activated ERK translocates in the nucleus. It
phosphorylates and activate ELK & SRK.
• Activated transcription factor promote the expression of gene.
• And form m-RNA then regulate the systemic body function.

17. 8. CONCLUSION :-
IGF-I /IGF-II is required of normal growth and
development. IGF-I is also called somatomedin ‘C’. IGF-I is produced
primorily by the liver production is stimulate by GH.
IGF-II is also known as somatomedin ‘A’. It play role in gastation
(growth promoting hormone) and folliculogenesis.
9. REFERENCE :-
• Mac. E. Hadley & Jon. E. Levine. – Endocrinology (6th edition).
• Chandra S. Negi – Introduction of Endocrinology.
• By Internet.