Essentials of Pathophysiology CHAPTER 31 ORGANIZATION AND CONTROL OF THE ENDOCRINE SYSTEM

Essentials of Pathophysiology
CHAPTER 31
ORGANIZATION AND CONTROL OF
THE ENDOCRINE SYSTEM
PRE LECTURE QUIZ TRUE/FALSE
The endocrine system uses chemical
substances called hormones as a means of
regulating and integrating body functions.
F
 All hormones can cross the cell membrane.
T  The hypothalamus controls the release of
pituitary hormones.
T  The pituitary gland has been called the master
gland because its hormones control the
function of many target glands and cells.
F  Glucagon, insulin, and epinephrine receptors
are examples of surface (second messenger)
receptors.
T

PRE LECTURE QUIZ
Feedback
Hypothalamus

Hormones exert their action by binding to high-affinity
_________________ located either on the surface or
inside the target cells.

Decreased hormone levels often produce an increase
in receptor numbers by means of a process called
_________________ ; this increases the sensitivity of
the body to existing hormone levels.

The ________________ and pituitary form a unit that
exerts control over many functions of several
endocrine glands as well as a wide range of other
physiologic functions.

Negative _________________ mechanisms regulate
the level of many of the hormones in the body.

Hormone secretions acting locally on cells other than
those that produced the hormone is known as a
___________________ action.
paracrine
Receptors
up-regulation
HORMONES
Hormones make cells react by attaching to
receptors on their membranes
 A cell will only respond if it has receptors for
the hormone

 Up-regulation:
the cell makes more hormone
receptors
 Down-regulation: the cell makes fewer hormone
receptors

Different cells respond differently to the
same hormone
HORMONES (CONT.)
• Hormones can affect cells
nearby or far away
•Endocrine – distant
•Paracrine – Nearby
•Autocrine – Self stimulating
QUESTION
Your patient has low levels of circulating thyroid
stimulating hormone. How will the cells of the
thyroid gland respond?
a. No response
b. Response will depend upon the levels of TSH.
c. Down-regulation
d. Up-regulation
ANSWER
Up-regulation
Rationale: When there is diminished hormonal
activity, cells have the ability to make more
hormone receptors and increase the sensitivity
of the existing receptors to the hormone. This
is called up-regulation.
d.
HORMONES (CONT.)
Hormones can be made of:

Amino acids


Proteins (peptide hormones)


Insulin, glucagon, trophic hormones
Cholesterol (steroid hormones)


Epinephrine, dopamine, T3, and T4
Cortisol, aldosterone, testosterone
Fatty acids

Ecosanoids
QUESTION
Tell whether the following statement is true or
false.
Steroid hormones are all derived from
cholesterol.
ANSWER
True
Rationale: The adrenal sex hormones,
glucocorticoids, and mineralocorticoids all
arise from cholesterol and have similar
chemical structures even though their
functions are slightly different.
SCENARIO
A man takes dopamine for paralysis caused by
his Parkinson disease.
 At first, a small dose of dopamine was all he
needed
 His symptoms improved significantly right after
taking it, but then he froze up again
 Now he needs a high dose, and the effects last
only a little while
Question:
 What has happened to his cells and their
receptors?
 The doctor has decided to try giving him an
MAO inhibitor along with his dopamine. Why?
AFTER HORMONES AFFECT BODY CELLS



They may be destroyed by enzymes at the
receptor site
 Epinephrine, dopamine
They may be taken up by cells and destroyed
 Peptide hormones
They may be destroyed in the liver and passed
out in the bile
 Steroid hormones
 T3 and T4
SCENARIO
A man with liver failure has developed:
 Hypokalemia
 Hypotension
 Hyperglycemia
 Repeated infections
Question:
 What hormone imbalances do you
suspect? Why?
HYPOTHALAMUS
The hypothalamus knows the state of the
body:
 Temperature
 Blood osmolarity
 Blood nutrients
 Blood hormone levels
 Inflammatory mediators in blood
 Emotions
 Pain
THE HYPOTHALAMUS MAKES RELEASING
HORMONES

Releasing
hormones
are sent to
the pituitary
via the
hypophyseal
portal system
Anterior
pituitary
Hypothalamus
Hypophyseal
portal
system
(Image reproduced from Bowne, P.S.
[2004]. CRH release tutorial. Used
with author’s permission.)
THE PITUITARY (MASTER
GLAND)
CREATES TROPHIC
HORMONES
Hypothalamus
makes releasing
hormones
Which are sent to the anterior
pituitary
The anterior pituitary releases its
stored trophic hormones into the
systemic circulation
(Image reproduced from Bowne, P.S. [2004]. CRH
release tutorial. Used with author’s permission.)
They tell other
endocrine organs
in the body to grow
and secrete their
hormones
QUESTION
Tell whether the following statement is true or
false.
The pituitary gland controls the release of thyroid
hormone.
ANSWER
True
Rationale: The pituitary gland (on a cue from the
hypothalamus) tells other organs or glands to
produce and secrete or inhibit the appropriate
hormones.
DISCUSSION
A man’s hypothalamus has no hormone receptors.
 What will happen to his production of:
 CRH
T3 and T4
 ACTH
FSH
 Cortisol
LH
 Testosterone
GnRH
 TRH
TSH
Question:
 What signs and symptoms do you expect him to
have?