Endocrine biochemistryyyyyyy in endocrinology.ppt

endo

1. BASIC ENDOCRINOLOGY

4. Functions of the body are regulated by 2 major
systems:
A.Nervous system
B.Endocrine system

5. •It has evolved to allow physiological processes
to coordinated and regulated by using chemical
messengers called hormones.
ENDOCRINE SYSTEM

6. 1.Maintenance of the internal environment in the body
(maintaining the optimum biochemical
environment)
2.Integration and regulation of growth and
development
3.Control, maintenance and instigation of sexual
reproduction, including gametogenesis, fertilization,
fetal growth and development and nourishment of
the newborn.
PRINCIPAL FUNCTIONS OF THE
ENDOCRINE SYSTEM

7. The endocrine system acts with nervous
system to coordinate the body's activities.
Both systems enable cells to communicate
with others by using chemical messengers.
The endocrine system uses chemical
messengers called hormones that are
transported by the circulatory system (blood).
They act on target cells that may be anywhere
in the body.
INTERRLATIONSHIP OF
ENDOCRINE AND NERVOUS
SYSTEMS

8. The endocrine system is slower than the
nervous system because hormones must travel
through the circulatory system to reach their
target.
Target cells have receptors that are specific to
the signaling molecules.

9. A chemical released from living cells that
travels some distance to target tissues to have a
biological effect.
i.Secreted in very small amounts
ii.Transported, usually, in the blood
iii.Target cells have specific receptors
iv.Regulates cell reactions by affecting gene
expression (often gene transcription factors)
HORMONES

10. Chemically hormones are of 3 basic types:
a)Proteins/ polypeptides
b)Amino acids
c)Steroids (cholesterol)
CHEMICAL CLASSES

11. Steroids
(cholesterol)
Cortisol
Aldosterone
Estrogen
Progesterone
Testosterone
Amino
Acids
Thyroxine
Triiodothyronine
Epinephrine
Nor-epinephrine
Proteins/
Polypeptides
Insulin
Glucagon
Parathormone
ADH
Oxytocin

12. Synthesis of Protein hormones
ACTH, LH, FSH, TSH, Glucogon

14. 2. Amines
1-2 amino acids
•Receptors
•Surface
–Intracellular
Thyroxin,
Epinephrine

15. 3. Steroid
•From cholesterol, lipophilic, enter target cell,
•Cytoplasmic or nuclear receptors (mostly)
•Activate DNA for protein synthesis
•Slower acting, longer half-life
cortisol, estrogen &
testosterone

16. •Before ovulation, small amounts of estrogen are
secreted from the ovary.
•Estrogen stimulates the release of gonadotropin-
releasing hormone (GnRH) from the
hypothalamus and luteinizing hormone (LH) from
the anterior pituitary
•GnRHalso stimulates the release of LH from the
anterior pituitary
•LH causes the release of additional estrogen from
the ovary. The GnRHand LH levels in the blood
increase because of this positive-feedback effect.
POSITIVE FEEDBACK
MECHANISM

18. Regulation of Hormones
UP-REGULATION
Increase affinity or number of receptors
GH increase on skeletal and liver
E2 on uterus
Also increase receptors of other hormones, e.g.
E2 up-regulate receptors of LH on ovaries

19. •During the estrus cycle, after ovulation, the ovary
begins to secrete progesterone in response to LH.
•Progesterone inhibits the release of GnRHfrom
the hypothalamus and LH from the anterior
pituitary.
•Decreased GnRHrelease from the hypothalamus
reduces LH secretion from the anterior pituitary.
GnRHand LH levels in the blood decrease
because of this negative-feedback effect
NEGATIVE FEEDBACK
MECHANISM

21. Regulation of Hormones
DOWN-REGULATION
Decrease the affinity or number of receptors
T
3down-regulate TRH on anterior pit.
gland

22. Regulation of Hormones

24. •Protein hormones:mostly unbound, free in
the blood
•Steroid hormones: Bound to a plasma protein
(high-affinity binding to globulin and low-
affinity to albumin). Cortisol to transcortin, sex
hormones to sex-hormone-binding globulin
(SHBG).
•Vitamin D:Bound to a globulin
(transcalciferin)
TRANSPORT

25. •Tyrosine-derived hormone:
•Thyroid hormones: Mostly bound to
thyronine-binding globulin (TBG) or
prealbumin (transthyretin)
•Catecholamine: Bound to albumin.
•Eicosanoids:Are not transported. They act as
autocrine or paracrine hormones

26. •Hormones dissolve in blood plasma and are
transported in free form or are reversibly
bound to plasma proteins
•Free form can diffuse from plasma into
interstitial fluid and affect cells
•As concentration of free hormone molecules
increase, more hormones molecules diffuse
from capillaries into interstitial spaces to bind
to target cells
DISTRIBUTION

27. •Lipid soluble hormones diffuse through capillary
cells. Water soluble hormones diffuse through
pores in capillaries called fenestrae.
•A large decrease in plasma protein concentration
can result in loss of a hormone from the blood
because free hormones are rapidly eliminated
from circulation through kidney or liver
•Hormones are distributed quickly because they
circulate in the blood

28. •Most hormones circulate in blood, coming into
contact with essentially all cells. However, a
given hormone usually affects only a limited
number of cells, which are called target cells. A
target cell responds to a hormone because it bears
receptors for the hormone.
•In other words, a particular cell is a target cell for
a hormone if it contains functional receptors for
that hormone, and cells which do not have such a
receptor cannot be influenced directly by that
hormone.
HORMONES AND RECEPTORS

30. •Portion of molecule where ligand binds is called
binding site.
•If the molecule is a receptor (like in a cell
membrane) the binding site is called a receptor
site.
•Ligand/receptor site is specific; e.g., epinephrine
cannot bind to the receptor site for insulin.
•The purpose of binding to target tissue is to elicit
a response by the target cell.
HORMONE (LIGAND)
INTERACTION WITH TARGET
TISSUE

31. •Receptor: integral proteins with receptor site at
extracellular surface. Interact with ligands that
cannot pass through the plasma membrane.
•Ligands
•Large proteins, glycoproteins, polypeptides;
smaller molecules like epinephrine and
norepinephrine.
MEMBERANE -BOUND
RECEPTORS

34. •Receptors: in the cytoplasm or in the nucleus
•Lipid soluble and relatively small molecules; pass
through the plasma membrane.
•React either with enzymes in the cytoplasm or
with DNA to cause transcription and translation.
•Hormones bind with intracellular receptor and
receptor-hormone complex activate certain genes,
causes transcription of mRNA and translation.
•Thyroid hormones, testosterone, estrogen,
progesterone, aldosterone, and cortisol.
INTRACELLULAR RECEPTORS

36. •Binding of hormone to receptor initiates a
series of events which leads to generation of
so-called second messengers within the cell
(the hormone is the first messenger). The
second messengers then trigger a series of
molecular interactions that alter the
physiologic state of the cell. Another term used
to describe this entire process is signal
transduction.
CONCEPT OF SECOND
MESSENGER

37. Second messenger systems are recognized in
cells:
1.G Protein–Linked Hormone Receptors
2.Adenylyl cyclase-cAMPSecond Messanger
system
3.The Cell Membrane Phospholipid Second
Messenger System
SECOND MESSENGERS

38. G Protein–Linked Hormone Receptors

39. Adenylyl cyclase-cAMP Second Messanger
system

41. The Cell Membrane Phospholipid Second
Messenger System

43. Enzymed–Linked Hormone Receptors

45. Steroid Hormones: Structure and
Action
Figure 7-7: Steroid hormone action

47. •Endocrine system, in concert with the nervous
system, is responsible for homeostasis.
Growth, development, reproduction, blood
pressure, concentrations of ions and other
substances in blood, and even behavior are all
regulated by the endocrine system.
•A hormone is a chemical substance ( peptide,
steroid, or amine), secreted into the circulation
in small amounts and delivered to target
tissues, where they produce physiologic
responses