Download pituitary gland and hypothalamus

PITUITARY GLAND AND
HYPOTHALAMUS
Anatomical Relations
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Pituitary
Sella Turcica
Optic Chiasm
Median Eminence
Mamillary Body
Cavernous Sinus
(not visible)
Subdivisions of the
Pituitary (Hypophysis)
• Adenohypophysis
(Anterior Pituitary)
– Pars Distalis
– Pars Intermedia
– Pars Tuberalis
• Neurohypophysis
(Posterior Pituitary)
– Pars Nervosa
– Infundibular Stalk
Adenohypophysis
Pars Distalis
Cells:
• Acidophils
– Somatotroph
– Lactotroph
• Basophils
– Gonadotrophs
– Thyrotrophs
• Corticotrophs
(can’t distinguish)
• Chromophobes
Hormones
• Prolactin/Growth Hormone Family
– Prolactin
– Growth Hormone
• Glycoprotein Family
– Thyroid Stimulating Hormone (TSH)
– Gonadotropins:
• Follicle Stimulating Hormone (FSH)
• Luteinizing Hormone (LH)
• Pro-opiomelanocortin Family
– ACTH
Prohormones
• Many small hormones, especially
peptide hormones, are synthesized
as part of a larger peptide.
• The large peptide is called a
prohormone
• The active hormone is cut out of the
larger prohormone by an enzyme.
• The prohormone generally is not
active.
POMC
Pars Intermedia
• MSH
– Pro-opiomelanocortin Family
– Alpha
– Beta
• Also in Hypothalamus
– Involved in regulating metabolism and
appetite
Pars Tuberalis
Hypothalamus
Hypothalamo-hypophyseal
Portal System
• Superior
hypophyseal artery
• Portal Vessels
• Capillary Bed of
Pars Distalis
Hypothalamic
Releasing Hormones
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Thyrotropin Releasing Hormone (TRH)
Corticotropin Releasing Hormone (CRH)
Gonadotropin Releasing Hormone (GnRH)
Growth Hormone Releasing Hormone (GRH)
Somatostatin (GIH)
Prolactin Inhibiting Hormone (PIH)
Feedback Control of
Anterior Pituitary
• Long Loop
• Short Loop
• Ultrashort Loop
• Amplitude
• Frequency
Pathologies
• Hypersecretion
• Hyposecretion
• Classification
– Primary (Pituitary’s Target Gland)
– Secondary (Pituitary)
– Tertiary (Hypothalamus)
• Pituitary adenomas
Growth Hormone (GH)
Chemistry
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Single chain protein, 191 amino acids
MW 21,500
2-disulfide bridges
Synthesized as part of a larger
protein, preGH (MW 28,000)
Function
• Stimulate Secretion of Insulin-like
Growth Factor 1 (IGF-1)
• Increase linear growth
• Increase protein synthesis
• Decrease protein catabolism
• Increase lipid catabolism
• Decrease carbohydrate uptake and
utilization
GHRH
Control
of
Secretion:
Somatostatin (GHIH)
Stimulates
• GRH
Inhibits the Secretion
of GH
– Neural regulation
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Diurnal Rhythms
Deep Sleep
Stress
Exercise
– Metabolic control
•  Blood Glucose
•  Blood Fatty Acids
•  Blood Amino Acids
• Somatostatin
Secretion
of GH
Feedback
• GH--Short Loop
• IGFs--Long Loop
• Metabolic control
–  Blood Glucose
–  Blood Fatty Acids
–  Blood Amino Acids
• Neural regulation
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Diurnal Rhythms
Deep Sleep
Stress
Exercise
Long-Loop
Diurnal
Feedback
Rhythms
Exercise
Sleep Regulation
Stress
GH
Short-Loop
Somatostatin
Feedback
Hypothalamus
Serum:
Glucose
Lipids
Amino
Acids
GRH
Ant. Pituitary
IGF1
Liver
IGF1
GH
Serum:
Glu.
Lipids
Amino
Acids
Other Target
Tissues
Pathologies
Hypersecretion
Gigantism
Acromegaly
Glucose Intolerance
• A form of Diabetes
• Caused by Hyperglycemia
• Leads to Type II Diabetes
Hyposecretion
Dwarfism
Prolactin (PRL)
• Chemistry
• Function:
• Control of Secretion
Control of PRL
Baby Suckles Nipple
Baby Weaned
Sensory Impulses to
Hypothalamus
Milk Production
Dopamine Secretion
Prolactin
Adrenocorticotropic
Hormone (ACTH)
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Chemistry
Biosynthesis
Function
Control of Secretion
Control of ACTH
Stress
Sleep
Hypothalamus
CRH
Ant. Pituitary
ACTH
Adrenal Cortex
Glucocorticoids
Thyroid Stimulating
Hormone (TSH)
• Chemistry
– Glycoprotein
– 2 Chains
• Function
– Stimulate production of thyroid
hormone (T4 & T3)
Control of TSH
Hypothalamus
TRH
Anterior
Pituitary
TSH
Thyroid
T4 & T3
T4
Gonadotropins
• Follicle Stimulating Hormone (FSH)
• Luteinizing Hormone (LH)
• Chemistry
– Glycoprotein
• Function
– Stimulate function of the reproductive
tract
Gonadotropin Control
Hypothalamus
GnRH
(FSH Only)
Ant. Pituitary
FSH
LH
Gonad
Inhibin
E2 & P or T
Posterior Pituitary
Pars Nervosa
Anatomical Structure
• An extension of
the hypothalamus
• Pituicytes
• Axons
• Supraoptic n.
– ADH
• Paraventricular n.
– Oxytocin
Hormones
Antidiuretic Hormone
(ADH, Vasopressin)
• Supraoptic nucleus
• Chemistry
• Receptors
– V1
– V2
Function:
• Vasoconstriction
– Increase Blood
Pressure
• Increase permeability
of collecting tubule
to H2O
Blood
Pressure
Control of ADH
Blood
Pressure
Vasoconstriction
Blood
Vessels
Supraoptic
Nucleus
Blood
Osmolality
Blood
Osmolality
Posterior
Pituitary
ADH
H2O
Absorption
Kidney,
Collecting
Duct
Diabetes insipidis
Oxytocin (Pitocin)
• Paraventricular nucleus
• Chemistry
• Receptors
– Phosphatidylinositol pathway
• Function
– Increases frequency and duration of
uterine smooth muscle contraction
– Stimulates milk “let down.”
Positive
Feedback
Delivery
Shuts
Control
of
Oxytocin
Loop Shut-Off
Suckling
On
Nipple
Off Positive
When
ChildLoop
is Full
Feedback
Unknown?
Hypothalamus
Labor
Contractions
Milk
Let-Down
Post. Pituitary
Mammary
Myoepithelial
Cells
Oxytocin
Uterine
Smooth
Muscle