Pituitary Gland Disorders
Topics to be Covered:
- Pituitary physiology including anatomy, histology and relevant embryology
- The clinical signs and symptoms of pituitary tumours including non-functioning
and functioning pituitary tumours
- The clinical features of Cushing’s disease. Acromegaly and prolactimonas will
be discussed
- The treatment of pituitary tumours will be outlined
- The causes, signs and symptoms and treatment of pituitary failure will be
discussed
- Diabetes insipidus and posterior pituitary dysfunction
The pituitary gland is made up of two lobes, anterior and posterior. Magnocellular
neurones project down from the hypothalamus and release hormones directly in the
blood. Oxytocin and vasopressin. So no synthesis of hormones in posterior pituitary.
The parvicellular neurones project into and release hormones into the median
eminence which can flow into the portal vessels (a portal vessel is a vessel that goes
from a capillary bed to a capillary bed, instead of capillary bed to vein) and into the
anterior pituitary to stimulate endocrine tissue to produce their hormones. There is no
direct connection between the hypothalamus and anterior pituitary.
The pituitary gland lies below the brain in the Sella Turcica, the anterior lobe
(adenohypophysis) is derived from an invagination of the roof of the embryonic
oropharynx known as Rathke’s pouch.
A notochordal projection forms the pituitary stalk which connects the gland to the brain
and also the posterior lobe of the pituitary (neurohypophysis).
The pituitary gland is surrounded by important structures which can be affected in
disease, namely in diseases such as adenomas which can press on the nearby structures.
Above the pituitary we have the optic chiasm, we have the internal carotid arteries on
the side. Underneath the sella turcica is the sphenoid sinus.
Pituitary cell type were originally classified by their staining characteristics with acidic
(orange-G) and basic (aldehyde fuscin) dyes.
Pituitary Hormones
Anterior:
ACTH is released which regulates the adrenal cortex
TSH controls production of thyroid hormones from the thyroid
GH controls growth
LH/FSH involved in reproductive control
Prolactin (PRL) is involved in breast milk production
Posterior:
ADH regulates water, it retains water (anti-duiris)
, Oxytocin causes uterine contraction in delivery but also in breast milk release
Nomenclature of Pituitary and Hypothalamic Hormones
‘trophe’ means food
LH and FSH = Gonadotrophin -- Hypothalamic hormone = Gonadotrophin Releasing
Hormone
Growth Hormone = Somatotrophin – Growth Hormone Releasing Hormone
TSH = Thyrotrophin – Thyrotrophin Releasing hormone
ACTH = Corticotrophin – Corticotrophin Releasing Hormone
The endocrine system is organised into layers
Primary layer is end organ
Secondary is pituitary
Tertiary is hypothalamus
The endocrine system is slow, long and about states of being.
The hypothalamus takes inputs of our senses and higher centres and integrates them.
These signals may be we’re stressed/threat in front of us/is there someone attractive in
front of me.
The hypothalamus then releases hormones saying stress/attraction/hunger.
But the hypothalamus is very small, so in order to dump enough hormone into blood the
neurones would have to be very large. So it doesn’t do this. Instead it puts it into the
portal vessels to the pituitary.
The pituitary has enough hormone to enter into blood and be diluted enough that they
can have their effects on the body.
Hypothalamus function is to integrate signal, function of pituitary is to amplify the
signal.
It takes time to synthesise peptide hormones so this wouldn’t be useful if it was needed
straight away. So the endocrine system is always primed with a little bit of stored
hormone to get into action straight away if needed.
But of course you also want to be able to switch it off quickly, so the peripheral
hormones switch off production of the central ones. So that the moment the response
starts, it is trying to be switched off again.
This is the principle of negative feedback <- allows system to be dynamic, be responsive
This principle is heavily used in the diagnosis of endocrine disorders
Clinical Presentation of Pituitary Tumours
When dealing with pituitary lesions we generally have three things to consider:
- Hormone hypersecretion (due to tumour secreting)
- Hormone deficiency status, tumour can squish the normal pituitary surrounding it
leading to decreased hormone release from those parts
Topics to be Covered:
- Pituitary physiology including anatomy, histology and relevant embryology
- The clinical signs and symptoms of pituitary tumours including non-functioning
and functioning pituitary tumours
- The clinical features of Cushing’s disease. Acromegaly and prolactimonas will
be discussed
- The treatment of pituitary tumours will be outlined
- The causes, signs and symptoms and treatment of pituitary failure will be
discussed
- Diabetes insipidus and posterior pituitary dysfunction
The pituitary gland is made up of two lobes, anterior and posterior. Magnocellular
neurones project down from the hypothalamus and release hormones directly in the
blood. Oxytocin and vasopressin. So no synthesis of hormones in posterior pituitary.
The parvicellular neurones project into and release hormones into the median
eminence which can flow into the portal vessels (a portal vessel is a vessel that goes
from a capillary bed to a capillary bed, instead of capillary bed to vein) and into the
anterior pituitary to stimulate endocrine tissue to produce their hormones. There is no
direct connection between the hypothalamus and anterior pituitary.
The pituitary gland lies below the brain in the Sella Turcica, the anterior lobe
(adenohypophysis) is derived from an invagination of the roof of the embryonic
oropharynx known as Rathke’s pouch.
A notochordal projection forms the pituitary stalk which connects the gland to the brain
and also the posterior lobe of the pituitary (neurohypophysis).
The pituitary gland is surrounded by important structures which can be affected in
disease, namely in diseases such as adenomas which can press on the nearby structures.
Above the pituitary we have the optic chiasm, we have the internal carotid arteries on
the side. Underneath the sella turcica is the sphenoid sinus.
Pituitary cell type were originally classified by their staining characteristics with acidic
(orange-G) and basic (aldehyde fuscin) dyes.
Pituitary Hormones
Anterior:
ACTH is released which regulates the adrenal cortex
TSH controls production of thyroid hormones from the thyroid
GH controls growth
LH/FSH involved in reproductive control
Prolactin (PRL) is involved in breast milk production
Posterior:
ADH regulates water, it retains water (anti-duiris)
, Oxytocin causes uterine contraction in delivery but also in breast milk release
Nomenclature of Pituitary and Hypothalamic Hormones
‘trophe’ means food
LH and FSH = Gonadotrophin -- Hypothalamic hormone = Gonadotrophin Releasing
Hormone
Growth Hormone = Somatotrophin – Growth Hormone Releasing Hormone
TSH = Thyrotrophin – Thyrotrophin Releasing hormone
ACTH = Corticotrophin – Corticotrophin Releasing Hormone
The endocrine system is organised into layers
Primary layer is end organ
Secondary is pituitary
Tertiary is hypothalamus
The endocrine system is slow, long and about states of being.
The hypothalamus takes inputs of our senses and higher centres and integrates them.
These signals may be we’re stressed/threat in front of us/is there someone attractive in
front of me.
The hypothalamus then releases hormones saying stress/attraction/hunger.
But the hypothalamus is very small, so in order to dump enough hormone into blood the
neurones would have to be very large. So it doesn’t do this. Instead it puts it into the
portal vessels to the pituitary.
The pituitary has enough hormone to enter into blood and be diluted enough that they
can have their effects on the body.
Hypothalamus function is to integrate signal, function of pituitary is to amplify the
signal.
It takes time to synthesise peptide hormones so this wouldn’t be useful if it was needed
straight away. So the endocrine system is always primed with a little bit of stored
hormone to get into action straight away if needed.
But of course you also want to be able to switch it off quickly, so the peripheral
hormones switch off production of the central ones. So that the moment the response
starts, it is trying to be switched off again.
This is the principle of negative feedback <- allows system to be dynamic, be responsive
This principle is heavily used in the diagnosis of endocrine disorders
Clinical Presentation of Pituitary Tumours
When dealing with pituitary lesions we generally have three things to consider:
- Hormone hypersecretion (due to tumour secreting)
- Hormone deficiency status, tumour can squish the normal pituitary surrounding it
leading to decreased hormone release from those parts
