2. Hormones are organic substances, produced
in small amounts by specific tissues
(endocrine glands), secreted into the blood
stream to control the metabolic and
biological activities in the target cells.
Hormones may be regarded as the chemical
messengers involved in the transmission of
information from one tissue to another and
cell to cell.
3. Endocrine hormones:
produced by ductless endocrine glands
mix to blood
have target organs
e.g. TH, LH, FSH
Autocrine hormones:
act on the same cells where they are synthesized.
e.g. interleukin-2
Paracrine hormones:
act on the cells adjacent/close to the cells from
where they are synthesized e.g. prostaglandins
6. 1. BASED ON CHEMICAL NATURE:
Peptide hormones : Insulin
Glucagon
ADH
Oxytocin
Steroid hormones: Sex hormones
Glucocorticoids
Mineralocorticoids
Amino acid derivatives: Epinephrine
Norepinephrine
Thyroid hormones
7.
8.
9.
10.
11.
12. Two divisions:
Anterior pituitary
(adenohypophysis)
Posterior pituitary
(neurohypophysis)
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Sits in hypophyseal fossa: depression in sella turcica of
sphenoid bone
Pituitary secretes 9 hormones
The Pituitary
1. TSH
2. ACTH
3. FSH
4. LH
5. GH
6. PRL
7. MSH
8. ADH (antidiuretic hormone), or vasopressin
9. Oxytocin
_________________________________________________________________
The first four are “tropic”
hormones, they regulate the
function of other hormones
________
13. 2. BASED ON MECHANISM OF ACTION
GROUP I: intracellular receptor (Lipophilic)
▪ Hormones bind to intracellular receptors (HRE in DNA)
to form receptor hormone complexes to carry out the
biochemical functions. They are derivatives of
cholesterol, lipophilic in nature and possess long half
lives.
14. GROUP II: surface receptor (Hydrophilic)
These hormones bind to cell surface receptors and
stimulate the release of second messengers which in
turn perform the biochemical function. They are
hydrophilic in nature and possess short half lives.
15. Hormones bind with HRE in DNA
Estrogens
Progestins
Androgens
Glucocorticoids
Mineralocorticoids
Calcitriol
Thyroid Hormones
17. (b)The second messenger is cGMP
Atrial natriuretic factor (ANF)
Nitric oxide (NO)
(c)The second messenger is phosphotidyl
inositol/calcium (or both)
Thyrotropin releasing hormone (TRH)
Gonadotropin releasing hormone (GnRH)
Gastrin
Cholecystokinin (CCK)
18. (d)The second messenger is unknown/
unsettled (Kinase/Phosphatase cascade)
Insulin
Growth hormone (GH)
Prolactin (PRL)
Oxytocin
Somatomedins (Insulin like growth factor) (IGF-
I, IGF-II)
19. Group I Hormones
Lipophilic in nature → cross plasma membrane by
diffusion
Act through intracellular receptors located either in
cytosol or nucleus
Duration of action is hours to days
Hormone first binds with receptor → forms HR-
complex → binds with the specific region on the DNA
called hormone responsive element (HRE) → causes
increased expression of specific genes →
transcription → translation → production of specific
proteins → carries biochemical action of hormone
20. HORMONE RESPONSE ELEMENT (HRE):-
Specific sequence present in DNA which binds HR
complex during lipophilic hormone action
HRE hormone specific
RESULT:-
Binding of HR complex to HRE → transcription →
mRNA → Translation (specific protein) →
Biochemical response
21. STRUCTURE OF RECEPTOR MOLECULES
Large, integral membrane proteins with
specificity & high affinity for hormones.
Hormone & receptor binding is reversible.
Initiate response without entering the cell.
Rapid response/ shorter duration of action
(seconds to hours).
Mediate effect through second messengers.
22. GROUP II HORMONES
These hormones are considered as first
messenger
Hormone binds to surface receptors
Carry the action through mediatory molecules
(second messengers)
Hormones → First messenger → Second
messenger → Activation of protein kinase →
phosphorylation of enzyme → biochemical
action.
23. Cyclic adenosine 3’,5’-monophosphate (cAMP)
consists of adenine, ribose & a phosphate.
Adenylate cyclase converts ATP to cAMP
cAMP is a second messenger for majority of
polypeptide hormones
cAMP binds with protein kinase and activates it to
carry out the phosphorylation for the biochemical
action of hormone
cAMP degrades to 5’ AMP by phosphodiasterase
29. (a) Humoral: in response to changing levels of
ions or nutrients in the blood
(b) Neural: stimulation by nerves
(c) Hormonal: stimulation received from
other hormones
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