1. Hormones attach to receptors on cells to trigger responses. Cells can up-regulate or down-regulate receptor production. 2. The document discusses different types of hormones including amino acids, proteins, steroids, and fatty acids. It also covers how hormones are deactivated after use. 3. The hypothalamus monitors the body's status and triggers hormone release from the pituitary gland, which then signals other endocrine glands to release their hormones.

1. Chapter 31
Mechanisms of Endocrine Control
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2. 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
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3. Hormones (cont.)
Hormones can
affect cells
nearby or far
away.
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Question
Your patient has low levels of circulating thyroid 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

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Answer
d. Up-regulation
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.

6. Hormones (cont.)
Hormones can be made of:
• Amino acids
– Epinephrine, dopamine, T3, and T4
• Proteins (peptide hormones)
– Insulin, glucagon, trophic hormones
• Cholesterol (steroid hormones)
– Cortisol, aldosterone, testosterone
• Fatty acids
– Ecosanoids
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Question
Tell whether the following statement is true or false:
Steroid hormones are all derived from cholesterol.

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Answer
True
The adrenal sex hormones, glucocorticoids, and
mineralocorticoids all arise from cholesterol and have
similar chemical structures even though their functions
are slightly different.

9. 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?
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10. 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
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Scenario
A man with liver failure has developed…
• Hypokalemia
• Hypotension
• Hyperglycemia
• Repeated infections
Question
• What hormone imbalances do you suspect? Why?

12. Hypothalamus
Hypothalamus knows the state of the body:
• Temperature
• Blood osmolarity
• Blood nutrients
• Blood hormone levels
• Inflammatory mediators in blood
• Emotions
• Pain
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14. Pituitary (Master Gland)
Creates Trophic Hormones
Hypothalamus makes
releasing hormones
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They tell other
endocrine
organs in the
body to grow
and secrete
their 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.)

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Question
Tell whether the following statement is true or false:
The pituitary gland controls the release of thyroid hormone.

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Answer
True
The pituitary gland (on a cue from the hypothalamus) tells
other organs or glands to produce and secrete or inhibit
the appropriate hormones.

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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?