CONTAINS BRIEF INFORMATION ABOUT Functional anatomy of pituitary gland

1. Functional anatomy of pituitary
gland
&
physiology of growth hormone
By: SHANKAR YADAV
MSc. Medical Physiology
Prachand Man Singh Rajbhandari
MSc. Medical Biochemistry
Vikram Shrestha
MSc. Medical Biochemistry
JAWAHARLAL NEHRU MEDICAL COLLEGE

2. Contents
• Introduction
• History
• Gross anatomy & development
• Histology
• Pituitary hormone
• Growth hormone
• Recent advances

3. Introduction
• Hypothalamic pituitary unit forms unique component
of endocrine gland
• Controls many aspects of human physiology
• From delivery & feeding of baby to growth &
development to adulthood
• Then to make individual capable of producing
progeny
• Controls various metabolism, water homeostasis,
thyroid & gonad functions

4. History
• In 150 AD, Galen –first to describe pituitary
• In early 18th century, De Haen described amenorrhea
in pituitary tumor patient
• In 1742 Joseph Lieutaud, demonstrated
hypothalamohypophyseal axis
• In 1772 Saucerotte first to describe Acromegaly
• In 1794 Frank, distinguished diabetes insipidus from
diabetes mellitus
• In 1838 Rathke described formation of gland

5. Contd….
• In 1887 Minkowiski, linked pituitary gland to number
of symptoms
• In 1892 Vassle Sacchi, showed that removal of pituitary
affect water & mineral metabolism
• In 1907 Schloffer, operate pituitary via nasal route
• In 1909 Aschner, demonstrated hypophysectomy in
growing animal cause Dwarfism
• In 1910 Cushing & team, linked between pituitary &
reproduction

6. Pituitary gland

8. Histology

9. Pituitary Hormones

10. Growth Hormone
Structure

11. Synthesis
• GH part of hypophyseal-pituitary axis.
• Synthesized in somatotroph cells
• Response to binding of GHRH to its receptor
• Activating gene transcription by cyclic adenosine
monophosphate-dependent mechanisms

12. Factors affecting synthesis
Factors influence secretion:
• peptide hormones GHRH Ghrelin
• sex hormone
• Choline and L-DOPA by stimulating GHRH
• Hypoglycemia, arginin by inhibiting somatostatin
release
• Deep sleep
• Niacin as nicotinic acid (Vitamin B3)
• Vigorous exercise

13. Factors inhibiting
• GHIH – paraventricular nucleus
• Circulating concentrations of GH & IGF
negative feedback mechanism
• Hyperglycemia
• Glucocorticoids
• Dihydrotesterone

14. Release
• Central and peripheral mechanisms.
• Centrally, its synthesis and release are promoted by
GHRH and inhibited by somatostatin
• Stress, exercise, malnutrition, and anorexia also
stimulate its secretion during the day.
• The release is counter-regulated by three negative-
feedback loops.

15. Circulation, half life & metabolism
Plasma level :
2-4 ng/mL
Half life :
0-20 minutes
Metabolic clearance rate:
350 L/day

16. Somatomedin
IGF-I (somatomedin -c) IGF-II (MSA)
secretion Independent of GH before birth
GH stimulates after birth
Independent of GH
Secretions are constant throughout
postnatal growth
Plasma level 10-170 ng/mL 300-800 ng/mL
Receptor Similar to insulin receptor Mannose-6-phosphate receptor
functions Growth stimulating activity
Control skeletal & cartilage growth
Growth during fetal development

17. Regulation of secretion

19. Mechanism of action

20. Actions
types
Direct IGFs mediated
Effect on growth IGF-I
Effect on metabolism IGF-II

21. Actions

22. Action contd…
On bone:
• GH promotes linear growth by acting on bone
cartilage & connective tissue
• GH stimulates osteoblast & osteoblast
• GH on growth mediated by somatomedins

23. Action contd…
Effects on mineral metabolism:
• Promotes bone mineralization on growing children
• Mediated by IGF-1, cause +ve nitrogen balance
• Ca2+ , Po4 , Na+
• Promotes retention of Na+, Cl- & K+

24. Applied aspects
Hyper secretion of GH
• Tumors of acidophilic cell – somatotrophs
• Depending upon age
1. Gigantism
2. Acromegaly
3. Mixed (acromegalic gigantism)

25. Gigantism
• Abnormal stature
• Large hand & feet
• Thick lips
• Bilateral
gynaecomastia
• Loss of libido
• Hyperglycemia

26. Acromegaly

27. Applied aspects cntd…
Hyposecretion
• Dwarfism:
1. Hypothalamic
2. Pituitary
3. Thyroid
4. ↓sed. liver IGF

28. Recent advances
• A recent study confirms unliganded GHR are in
dimerised state
• Cultured human fibroblast can produce IGF-I
• GH acts on some target to induce Somatomedin-c,
production which in turn acts locally at the site of
production

29. References
• Text book of medical physiology
Indu Khurana, section -8 chapter 2, page no. 688-703
• Text book of medical physiology, 2nd edition
by G.K. & Pravati Pal,. Section-VI chapter 44 page
no. 323-339
• Text book of physiology, 5th edition by A.K. Jain
Volume -II, unit- IX page no. 683