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The Sella Turcica
Home of the Pituitary Gland
What Do the Pituitary and
Hypothalamus Do?
• Pituitary Gland
• Hypothalamus
– Secretes/releases hormones –
that affect endocrine glands in
the body
– Regulate other hormones as a –
“hormone control center”
– Has effects on blood pressure, –
growth, metabolism, water
retention, body temperature,
sexual development, and
pregnancy.
Receives
stimulation/information from
various parts of the brain
Secretes hormones that regulate
the pituitary gland (anterior)
Secretes hormones that are
released directly by the pituitary
(posterior)
2
The Pituitary and The Hypothalamus
The Two Lobes of the Pituitary and
Relationship to other Structures
Pituitary Anatomy and Two Modes of
Secretion
2 lobes of the pituitary
2 Types of hypothalamic neurons
2 blood vessel system
Neuron Review
1) Receive Signal at
dendrites
2) Generate “action
potential”
3) Propagate action
potential along axon
4) Signal next cell
with
Neurotransmitters
at a synapse
Various Brain
Cells
Regulation of
Hypothalamic
Secretion by Neurons
using “Classical”
Neurotransmitters
(e.g.serotonin, dopamine)
Hypothalamus
Cell
Pituitary Anatomy and Two Modes of
Secretion
Posterior pituitary hypothalamic neurons create
hormones and release them directly into the
bloodstream
The Posterior
Pituitary Gland Isn’t
a Gland
– Posterior pituitary hormones
actually come from the
hypothalamus
– Hormones:
– Oxytocin -> Childbirth,
breastfeeding, love.
– Vasopressin ->water
retention
Pituitary Anatomy and Two Modes of
Secretion
Hypothalamic neurons associated with the
Anterior Pituitary release “tropic” hormones
into the “portal vessels.” These travel to the
Anterior pituitary.
Hypothalamus
Releasing Factor
(topic hormone) on the
Anterior Pituitary
– Example
– Growth Hormone Releasing
Hormone (GHRH) -> Portal
System
– Portal System -> Anterior
Pituitary
– Anterior Pituitary ->
Growth Hormone
Melmed, S et al (2011) Williams
Textbook of Endocrinology, Figure 3-7
Hypothalamic Hormones That Regulate
5 Anterior Pituitary Secretions
• Pituitary hormones with
positive and negative
hypothalamic regulators
• Pituitary hormones with
positive hypothalamic
regulators
– Growth hormone controlled by – Thyrotropin releasing hormone
• GHRH (+)
(TRH)-> Thyrotropin
• Somatostatin (-)
– Corticotropin releasing
– Prolactin controlled by
hormone (CRH)
• Prolactin inhibitory factor
> Corticotropin
(PIF; dopamine) (-)
– Gonadotropin releasing
• Prolactin releasing factor
hormone (GnRH)
(PRF) (+)
-> Gonadotropin
Hormones & Cell Types
of Anterior Pituitary
Growth hormone (GH): Somatotrope
Prolactin (PRL): Lactotrope
Thyroid stimulating hormone (TSH):
Thyrotrope
Adrenocorticotropic hormone (ACTH)
: Corticotrope
Follicle stimulating hormone (FSH)
and Luteinizing hormone (LH):
Gonadtrope
Heaney AP & Melmed S (2004) Nat Rev Cancer, 4, 285-295
Homeostasis: Negative Feedback
Systems
Keep body functions in balance
How does this apply to Pituitary hormones?
Control of Water Metabolism by Vassopressin (AVP)
Hypothalamus
Increase
in Blood
Water
Loss
viscosity
AVP
Stimulate
Thirst
Drink
Decreased
Blood Viscosity
Retain
Water
Control of Water Metabolism by Vassopressin (AVP)
Hypothalamus
Increase
in Blood
Water
Loss
viscosity
AVP
Stimulate
Thirst
Drink
Retain
Water
Decreased
Blood Viscosity
16
Thyroid Hormone Feedback System
17
Anterior Pituitary Axes
Hypothalamic Control, Hormones and their Targets and
Feedback Control
Adrenal Axis
Thyroid Axis Gonadal Axis
Growth HormoneProlactin
Axis
Axis
Melmed, S et al (2011) Williams Textbook of Endocrinology, Figure 8-6
MRI of Normal Pituitary
MRI of Large Pituitary Tumor
Microadenoma
Macroadenoma
Schlechte, JA (2003) NEJM, 349, 2035-2041
Effects of Pituitary Adenoma
– Visual field defects due to
growth pushing on the optic
chiasm
– Increasing Inter Cranial
Pressure
– Headaches
– Hyperpituitarism
– Too much production of
one or several hormones
Hyperpituitarism
Acromegaly
Pituitary Giantism
Key Points
– The Hypothalamus produces hormones that:
– Are released by the posterior pituitary
– Raise or lower production of anterior pituitary hormones
– The pituitary gland:
– Produces hormones that regulate other endocrine glands in
the body
– Each of these hormones has a feedback loop that maintains
homeostasis
– Disease of the pituitary or hypothalamus can have serious effects