Download Hypothalamus

Chapter 32
Disorders of Endocrine Control of
Growth and Metabolism
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HypothalamusPituitary Axis
• Releasing hormones
from hypothalamus tell
the pituitary what to
release into the blood
• Trophic hormones from
the pituitary tell specific
peripheral glands to
grow and produce their
hormones
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Hormone Disorders
Tertiary: abnormality in
stimulation from the
hypothalamus
Secondary: abnormality
in stimulation from the
pituitary
Primary: abnormality in
the gland
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Pituitary
Hormones
Growth
hormone
FSH
and LH
TSH
stimulate
gonads
stimulates
thyroid
ACTH
stimulates
adrenal
cortex
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Question
Which hormone(s) is/are secreted by the ovaries and
testes?
a. GH
b. FSH & LH
c. TSH
d. ACTH & GH
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Answer
b. FSH & LH
Gonads are sex organs (ovaries and testes). These organs
secrete follicle-stimulating hormone (FSH) and
luteinizing hormone (LH).
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The Hypothalamus Controls Growth
Hormone Release
Hypothalamus
• GH secretion stimulated by:
– Hypoglycemia, fasting,
starvation
GHRH
stimulates
– Stress
Somatostatin
inhibits
• GH inhibited by:
– Increased glucose
levels, free fatty acid
release, and obesity
– Cortisol
Anterior pituitary
Growth
hormone
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Functions of Growth Hormone
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Growth Hormone Deficiency
• Idiopathic GH deficiency
– Lacks hypothalamic GHRH
• Pituitary tumors, agenesis of the pituitary
– Cannot produce GH
• Laron-type dwarfism
– Hereditary defect in IGF production
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Growth Hormone Excess
• In childhood: gigantism
• In adulthood: acromegaly
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Question
Tell whether the following statement is true or false:
GH deficiency may result in dwarfism.
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Answer
True
Laron-type dwarfism is caused by a genetic inability to
produce normal amounts of GH.
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The Hypothalamus Controls Gonadal
Hormone Release
Hypothalamus
• Excessive GnRH secretion
can be stimulated by:
– Hypothalamus tumors
– Pituitary tumors
• Giving high levels of GnRH
causes the pituitary to
become less responsive and
reduces the effects of
abnormal GnRH secretion
GnRH
stimulates
anterior pituitary
FSH
LH
production of gametes
and gonadal hormones
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Thyroid Control
• Thyroid releases T3
and T4
• Both are carried by binding
proteins
• T3 stimulates metabolism
• T4 is inactive until converted
into T3 in the tissues
• Both exert negative feedback
on the hypothalamus
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Thyroid Insufficiency Due to Lack of I• T3 and T4 are not made
• There is no negative feedback to the
hypothalamus
• TRH and TSH continue to be made
• If it is able, the thyroid will grow in response to
the TSH
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Thyroid Imbalances
• Hypothyroidism
– Congenital
– Acquired
º Hashimoto thyroiditis
º Thyroidectomy
• Hyperthyroidism (thyrotoxicosis)
– Graves disease
– Thyroid tumors
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Question
Tell whether the following statement is true or false:
Simple goiter is caused by increased production of thyroid
hormone.
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Answer
False
Simple goiter is the result of iodine (I) insufficiency. Since
I is necessary in order to produce thyroid hormone, a
deficiency results in low serum levels of T3/T4. This
causes TSH to stimulate the thyroid gland to make more
hormone (which it cannot do because it needs I). The
cells of the thyroid gland hypertrophy in an effort to
function (make thyroid hormone).
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Major Adrenal Cortical Hormones
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Actions of Cortisol
cortisol
catabolism increased
plasma
proteins
increased
muscle
breakdown
free fatty
acids
increased
immune/
inflammatory
systems
suppressed
SNS response
increased
blood glucose
increased
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Adrenal Cortical Disorders
• Adrenal cortical insufficiency: inability to make all 3 hormones
– Primary adrenal cortical insufficiency (Addison disease)
– Secondary adrenal cortical insufficiency
– Acute adrenal crisis
• Excessive adrenal secretion
– Glucocorticoid hormone excess (Cushing syndrome)
– Hyperaldosteronism
• Congenital adrenal hyperplasia
– Decreased cortisol synthesis; other hormones may be
increased or decreased
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Clinical Manifestations of Addison Disease
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Clinical Manifestations of Cushing
Syndrome
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Scenario
Three men have adrenal problems…
• One has hypoaldosteronism, one has an inability to make
cortisol, and one has an inability to make testosterone.
Question
• Which of them is most likely to develop:
• Hypotension?
• High CRH levels?
• Hypoglycemia?
• Hypervirilization?
• Decreased libido?
• Hyperkalemia?
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Scenario
Two women have benign pituitary tumors…
• One woman has lost weight and complains of being
hot all the time; she presents as thin and nervous,
with tachycardia and exophthalmos
• The second woman has gained weight in her
abdomen and presents with a round face and thin
arms and legs with stretch marks; she says that at
her last checkup her doctor told her she was prediabetic
Question
• What hormones are being secreted by the pituitary
tumors in these patients? Why?
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