Introduction to the Hypothalamic-Pituitary Axis Flashcards
Autocrine signalling is a form of cell signalling in which a cell secretes a hormone or chemical messenger that binds to autocrine receptors on …
that same cell, leading to changes in the cell

Paracrine signalling is a form of cell-to-cell communication in which a cell produces a signal to induce changes in …
nearby cells, altering the behaviour of those cells.

Endocrine action is where the hormone is …
distributed in blood and binds to distant target cells.
… action: the hormone is distributed in blood and binds to distant target cells.
… action: the hormone acts locally by diffusing from its source to target cells in the neighborhood.
… action: the hormone acts on the same cell that produced it.
… action: neuronal cells that secrete chemicals which enter the bloodstream and flow to a distant site and act on target cell receptors.
Endocrine action: the hormone is distributed in blood and binds to distant target cells.
Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood.
Autocrine action: the hormone acts on the same cell that produced it.
Neuroendocrine action: neuronal cells that secrete chemicals which enter the bloodstream and flow to a distant site and act on target cell receptors.

Where does the pituitary lie?
in the brain, just behind the eyes

The pituitary has two parts, the … pituitary and the … pituitary
anterior pituitary
posterior pituitary

Anatomy of the pituitary:
The pituitary gland is a pea-sized oval structure, suspended from the underside of the brain by the pituitary … (known as the infundibulum). It sits within a small depression in the … bone, known as the sella turcica (‘’Turkish saddle’’).
It consists of how many parts? Where are they derived from?
It has it’s own pituitary … which protects it inside the skull
stalk
sphenoid bone
2 parts - posterior derived from hypothalamus and anterior derived from roof of pharynx, called Rathke’s pouch
pituitary fossa

Pituitary gland blood supply:
- It has a … sinusoidal circulation
- circulation is lined by …
- … … is above the pituiatry = linked to pituitary tumours
- portal sinusoidal circulation
- circulation lined by sinusoids
- optic chiasm is above the pituitary
What is shown in this image?

Pituitary gland anatomy
What is shown in this image?

Bottom - pituitary tumour pressing on the optic chiasm
Anatomy of pituitary image

What is shown in the image?

Drawings by Leonardo de Vinci - showing relationship between the third ventricle and hypothalamus
The hypothalamus
- Integrates functions that maintain chemical and temperature …
- Functions with the … system
- Controls the release of … from the anterior and posterior pituitary
- Integrates functions that maintain chemical and temperature homeostasis
- Functions with the limbic system
- Controls the release of hormones from the anterior and posterior pituitary
Hypothalamic releasing hormones
- The median … secretes small peptides and …
- These hormones control the secretion of gonadotropes, somatotropes, lactotropes, corticotropes and thyrotropes
- Discovery of the hypothalamic releasing hormones and the blood supply connecting the hypothalamus and pituitary led to the Nobel Prize physiology/medicine in … for Andrew Schally and Roger Guillemin.
- The median eminence secretes small peptides and dopamine
- These hormones control the secretion of gonadotropes, somatotropes, lactotropes, corticotropes and thyrotropes
- Discovery of the hypothalamic releasing hormones and the blood supply connecting the hypothalamus and pituitary led to the Nobel Prize physiology/medicine in 1977 for Andrew Schally and Roger Guillemin.
Gonadotropes cells are endocrine cells in the anterior pituitary that produce the gonadotropins, such as the … hormone and … hormone
- Follicle stimulating hormone - FSH
- Luteinizing hormone - LH
Somatotrophs are the cells in the anterior pituitary that release … … hormone (also called somatotropin). They constitute about …-…% of the anterior pituitary cells.
- pituitary growth hormone
- 30-40% of anterior pituitary cells
A lactotropic cell is a cell in the anterior pituitary which produces … in response to hormonal signals including dopamine which is … and thyrotropin-releasing hormone which is stimulatory.
- produces prolactin
- dopamine is inhibitory
- thyrotropin-releasing hormone is stimulatory
- … is made in the corticotroph cells of the anterior pituitary gland, where it is released in bursts into the bloodstream and transported around the body.
- ACTH
Thyrotropes (also called thyrotrophs) are endocrine cells in the anterior pituitary which produce … …. hormone in response to … … hormone. Thyrotropes consist around …% of the anterior pituitary lobe cells
Thyrotropes (also called thyrotrophs) are endocrine cells in the anterior pituitary which produce thyroid stimulating hormone in response to thyrotropin releasing hormone. Thyrotropes consist around 5% of the anterior pituitary lobe cells
Who discovered the hypothalamic releasing hormones?
Andrew Schally and Roger Guillemin - led to Nobel prize in 1977
Hypothalamic releasing hormones
- GnRH (… releasing hormone)
- … AA, isolated in 1971
- Stimulates secretion of … and …
- GnRH (Gonadotropin releasing hormone)
- 10 AA, isolated in 1971
- Stimulates secretion of FSH and LH
Hypothalamic releasing hormones
- SS, known as (…)
- Inhibits … hormone secretion
- SS (Somatostatin)
- Inhibits growth hormone secretion
Hypothalamic releasing hormones
- Dopamine
- Inhibits … secretion
- Dopamine
- Inhibits prolactin secretion
Hypothalamic releasing hormones
- … releasing factor (CRF)
- … AA, isolated in 1981
- stimulates secretion of …
- Corticotropin releasing factor (CRF)
- 41 AA, isolated in 1981
- stimulates secretion of ACTH
Hypothalamic releasing hormones
- … releasing hormone (TRH)
- … AA, isolated in 1969
- Stimulates … secretion
- thyrotropin releasing hormone (TRH)
- 3 AA, isolated in 1969
- Stimulates TSH secretion
Hypothalamic releasing hormones
- GHRH (… … releasing hormone)
- … AA … protein receptor secretin family
- Stimulates … secretion
- GHRH (growth hormone releasing hormone)
- 44 AA, G protein receptor secretin family
- Stimulates GH secretion
Structure of pituitary and release of hypothalamic releasing hormones
- hypothalamus has neurosecretory cells that secrete … hormones
- these travel down the … circulation in the pituitary … to the … pituitary (where they have their action)
- neurosecretory cells also secrete posterior pituitary hormones
- posterior pituitary has more … tissue
- hypothalamus has neurosecretory cells that secrete releasing hormones
- these travel down the portal circulation in the pituitary stalk to the anterior pituitary (where they have their action)
- neurosecretory cells also secrete posterior pituitary hormones
- posterior pituitary has more neurological tissue
Hormones from the hypothalamus are delivered to the … pituitary via the hypothalamic-… portal system. It is … and has … which allows free access and movements of these peptides.
Hormones from the hypothalamus are delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system. It is sinusoidal and has pores which allows free access and movements of these peptides.

Hypothalamic–hypophyseal portal system
- hypothalamus cells - … and … hormones - flow down … system - to the … pituitary - cause this to produce or inhibit … pituitary hormones
- enter … circulation and travel to distal … tissues and have affect
- cells in hypothalamus also have … (ADH) and … - into … pituitary - directly into … circulation
- hypothalamus cells - releasing and inhibiting hormones - flow down portal system - to the anterior pituitary - cause this to produce or inhibit anterior pituitary hormones
- enter systemic circulation and travel to distal target tissues and have affect
- cells in hypothalamus also have vasopressin (ADH) and oxytocin - into posterior pituitary - directly into systemic circulation

- The …-… axis (HPA axis) is an interactive neuroendocrine unit comprising of the …, the … gland, and the … glands.
- The HPA axis plays key roles in basal … and in the body’s response to …
The hypothalamic-pituitary axis (HPA axis) is an interactive neuroendocrine unit comprising of the hypothalamus, the pituitary gland, and the adrenal glands.
- The HPA axis plays key roles in basal homeostasis and in the body’s response to stress

Adrenal-Pituitary Axis
- For … Regulation (the main …)
- …-releasing hormone (CRH) is secreted by the hypothalamus
- CRH travels in the blood to anterior pituitary - to corticotrophs
- Production of …
- This is released into the bloodstream and travels to the adrenal glands, where it binds to specific receptors on the adrenal ….
- The binding of ACTH to the receptors on the adrenal cortex stimulates the release of … into the bloodstream.
- involves what mechanism?
- For Cortisol Regulation (main glucocorticoid)
- Corticotropin-releasing hormone (CRH) is secreted by the hypothalamus
- CRH travels in the blood to anterior pituitary - specifically to corticotrophs
- These produce ACTH
- This is released into the bloodstream and travels to the adrenal glands, where it binds to specific receptors on the adrenal cortex.
- The binding of ACTH to the receptors on the adrenal cortex stimulates the release of cortisol into the bloodstream.
- Negative feedback mechanism

Thyroid Axis
- …-releasing hormone (TRH) is released from the hypothalamus
- TRH travels in the blood to anterior pituitary - to thyrotrophs
- Production/release of …
- This is released into the bloodstream and travels to the thyroid gland
- Stimulatory effect to promote production of both … and …
- involves what mechanism?
- Thyrotropin-releasing hormone (TRH) is released from the hypothalamus
- TRH travels in the blood to anterior pituitary - to thyrotrophs
- Production/release of thyroid stimulating hormone - TSH
- This is released into the bloodstream and travels to the thyroid gland
- Stimulatory effect to promote production of both T3 and t4
- negative feedback mechanism

__Gonodal axis
- GnRH (… releasing hormone) is released from the hypothalamus
- flows through the gonadotropes in pituitary
- … and … are both produced
- direct effect to stimulate either testes to produce … and … or the ovaries to make … and …
- GnRH (gonadotropin releasing hormone) is released from the hypothalamus
- flows through the gonadotropes in pituitary
- FSH and LH are both produced
- direct effect to stimulate either testes to produce testosterone and sperm or the ovaries to make oestrogen and eggs

Growth hormone axis
- GHRH (known as…)
- Somatostatin is the … (these both act in concert to have a tonic control of secretion of growth hormone)
- Causes secretion of growth hormone
- Acts on the … (part of body?) to make a hormone called …-1
- mediates it’s effects
- GHRH (known as growth hormone releasing hormone)
- Somatostatin is the inhibitor (these both act in concert to have a tonic control of secretion of growth hormone)
- Secretion of growth hormone
- Acts on the liver (part of body?) to make a hormone called IGF-1
- mediates it’s effects

Prolactin axis
- … is the main controller of prolactin secretion and acts in a … manner
- The … agonist cause … in prolactin whereas … antagonist … prolactin levels
- dopamine is the main controller of prolactin secretion and acts in a negative manner
- The dopamine agonist cause reduction in prolactin whereas dopamine antagonist raise prolactin levels

Negative-feedback controls - Long and short loop reflexes
- stimulus on the …
- causing … hormone to be released
- flows to … pituitary
- … hormone produced
- travels in … to a distal endocrine system/target tissue
- creates additional hormones
- long loop negative feedback from hormone and also the short loop negative feedback from hormone (e.g long = … acting on anterior pituitary and hypothalamus, also short = … acting on hypothalamus in addition)
- stimulus on the hypothalamus
- causing trophic hormone to be released
- flows to anterior pituitary
- trophic hormone produced
- travels in bloodstream to a distal endocrine system/target tissue
- creates additional hormones
- long loop negative feedback from hormone and also the short loop negative feedback from hormone (e.g long = cortisol acting on anterior pituitary and hypothalamus, also short = ACTH acting on hypothalamus in addition)
What hormones does the anterior pituitary make? (6 hormones)
- Thyroid stimulating hormone (TSH) - affects thyroid
- Adrenocorticotropic hormone (ACTH) - affects adrenals - only affects cortisol production (aldosterone etc not effected by ACTH)
- Growth hormone (GH) - multitude of effects but direct effect on liver to make IGF-1
- Follicle stimulating hormone (FSH) - act on gonads in girls and boys
- Luteinizing hormone (LH) - act on gonads in girls and boys
- Prolactin (Prl) - acts on the breasts and also acts as contraceptive - dampens down the ovaries

What hormones does the posterior pituitary make? (2 hormones)
- Arginine Vasopressin (AVP) - ADH
- Oxytocin

There are 5 phenotypically distinct cells in the anterior lobe of the pituitary:
- Somatotropes (…% of anterior lobe cells) - these synthesize … hormone - a polypeptide
- Lactotropes (…-…% of cells) - these synthesize … - a polypeptide
- Corticotropes (…-…% of cells) - these synthesize … - endorphin, peptide varying from 31-20 AA
- Thyrotropes (…% of cells) - Produce …, known as … - a glycoprotein
- Gonadotropes (…-…% of cells) - Produce … hormone and … … hormone - both glycoproteins
- Somatotropes (50% of anterior lobe cells) - these synthesize growth hormone - a polypeptide
- Lactotropes (10-20% of cells) - these synthesizeprolactin - a polypeptide
- Corticotropes (5-10% of cells) - these synthesize ACTH - endorphin, peptide varying from 31-20 AA
- Thyrotropes (5% of cells) - Produce thyrotropin known as TSH - a glycoprotein
- Gonadotropes (10-15% of cells) - Produce Luteinizing hormone and Follicle stimulating hormone - both glycoproteins
What is shown in this image? (pituitary)

Structure of anterior lobe cells
What is shown in this image? (anterior pituitary cell type)

Electron micrograph of a somatograph (growth hormone secreting cell)
3 levels of integration - Endocrine control
- hypothalamus - … hormones produced
- … hormones
- … site - hormones secreted here
- hypothalamus - precursor hormones produced
- pituitary hormones
- distal site - hormones secreted here
Growth hormone
- Molecular weight of …
- bound to … … bound protein and … … bound protein
- half life varies from … to … minutes
- … to … secretion
- predominantly secreted at …
- acts on … to produce …
- Molecular weight of 22,000
- bound to high affinity bound protein and low affinity bound protein
- half life varies from 6 to 20 minutes
- pulse to pulse secretion
- predominantly secreted at night
- acts on liver to produce IGF1

As well as acting on the liver, … hormone also has a major effect on a lot of bones and structural tissues. It also plays a role in adults to keep … in good shape and for regeneration after …
As well as acting on the liver, growth hormone also has a major effect on a lot of bones and structural tissues. It also plays a role in adults to keep muscle in good shape and for regeneration after exercise

Prolactin
- Prolactin is a … amino acid peptide, synthesised in the … cells of the anterior pituitary
- major function of prolactin is … production - what stimulates it’s ejection?
- release is tonically inhibited by …
- inhibits … function (nature is contraceptive)
- Prolactin control is a … influence
- Prolactin is a 199 amino acid peptide, synthesised in the lactotrophe cells of the anterior pituitary
- major function of prolactin is milk production - what stimulates it’s ejection? - oxytocin
- release is tonically inhibited by dopamine (PIH)
- inhibits gonodal function (nature is contraceptive)
- negative influence
Thyroid and TSH
- Regulation of thyroid synthesis and secretion via hypothalamic-pituitary-thyroid axis
- Hypothalamus - … released - goes to the … pituitary - secretion of … - travels to thyroid - … and … produced - also growth of thryoid - … feedback on the hypothalamus and the anterior pituitary
- Regulation of thyroid synthesis and secretion via hypothalamic-pituitary-thyroid axis
- Hypothalamus - TRH released - anterior pituitary - TSH - thyroid - T3 and T4 produced - also growth of thyroid - negative feedback on the hypothalamus and the anterior pituitary

ACTH and the Adrenal Glands
- Adrenal medulla - does ACTH affect it?
- Adrenal cortex
- 3 specific zones and each produces a specific class of steroid hormone
- list the zones and hormones they produce
ACTH only controls … production, not the others
- Adrenal medulla - does ACTH affect it? - NO
- Zona glomuerulosa - mineralocorticoids
- Zona fasciculata - glucocorticoids
- Zona reticularis - androgens
- ACTH only affects glucocorticoid production (cortisol)

- Cortisol has a … variation - usually high in the … and low at …
- Stressful stimulus causes … of cortisol
Cortisol has a diurnal variation - usually high in the morning and low at night
- stressful stimulus causes cortisol release

Glycoproteins LH/FSH and the Gonodal axis
- Long polypeptides (>… AA) bound to one or more … group
- Long polypeptides (>100 AA) bound to one or more carbohydrate group
FSH/LH in females
- control the menstrual cycle
- … formation and formation of …
- LH more to do with production of … and FSH more to do with production of …
- both needed to develop these things
- control the menstrual cycle
- oestrogen formation and formation of eggs
- LH more to do with production of oestrogen and FSH more to do with production of eggs
- both needed to develop these things

Menstrual cycle
- The menstrual cycle is orchestrated by the … system through the complex interaction of the hypothalamus, pituitary and gonads (known as the …-…-… axis). The entire menstrual cycle lasts around … days, with the cycle beginning on the first day of menstruation and … occurring at approximately day 14.
- Surge of FH & LH around …
- The menstrual cycle is orchestrated by the endocrine system through the complex interaction of the hypothalamus, pituitary and gonads (hypothalamic-pituitary-gonadal axis). The entire menstrual cycle lasts around 28 days, with the cycle beginning on the first day of menstruation and ovulation occurring at approximately day 14.
- Surge of FH & LH around ovulation

FSH/LH in males
- FSH and LH affects production of … and …
- LH more to do with production of …
- FSH more to do with production of …
- FSH and LH affects production of sperm and testosterone
- LH more to do with productioo of testosterone
- FSH more to do with production of sperm

Posterior pituitary
- Comprised of the endings of … from cell bodies in the … (… and …)
- Axons pass from the … to the posterior pituitary via the … tract
- Posterior pituitary hormones are synthesized in the cell bodies of neurons in the … and … nuclei
- Comprised of the endings of axons from cell bodies in the hypothalamus (supraoptic and paraventricular)
- Axons pass from the hypothalamus to the posterior pituitary via the hypothalamohypophysial tract
- Posterior pituitary hormones are synthesized in the cell bodies of neurons in the supraoptic and paraventricular nuclei
- Hormones synthesized in the hypothalamus are transported down the axons to the endings in the … pituitary
- Hormones are stored in … in this part of the pituitary until release into the circulation
- Principal hormones are … and …
- Hormones synthesized in the hypothalamus are transported down the axons to the endings in the posterior pituitary
- Hormones are stored in vesicles in this part of the pituitary until release into the circulation
- Principal hormones are vasopressin (ADH) and oxytocin

What is shown in this image?

Synthesis, storage and release of posterior pituitary hormones
Two embryological origins for the pituitary gland - the … and the …
Two embryological origins for the pituitary gland - the adenohypophysis and the neurohypophysis
Neurohypophysis
- outgrowth from the …
- median … - nerve endings and capillaris
- … … (posterior or nerual lobe) - contains nerve endings and capillaries
- outgrowth from the hypothalamus
- median eminence - nerve endings and capillaris
- pars nervosa (posterior or nerual lobe) - contains nerve endings and capillaries
What is shown in this image? (posterior lobe of pituitary)

Neurosecretory nerve terminals in contact with a capillary in the posterior lobe
The two posterior hormones are small … that are really structural in nature
The two posterior hormones are small peptides that are really structural in nature

Antidiuretic Hormone (ADH)
-
Antidiuretic actions
- … permeability of the … ducts to water
- V… receptors
-
Vasopresser actions
- … vascular … muscle cells
- V… receptors, non-…
-
Antidiuretic actions
- increases permeability of the collecting ducts to water
- V2 receptors
-
Vasopresser actions
- constricts vascular smooth muscle cells
- V1 receptors, non-hormonal
Kidney - ADH
- ADH causes urine to become more …
- more water is brought into …
- ADH causes urine to become more concentrated
- more water is brought into circulation

Vasoconstricting action of ADH
- … BP/circulating volume
- … production
- increase water …, increase …
- Low BP/circulating volume
- ADH then produced
- increases water production, increase BP

Oxytocin
- Important in Breast-feeding
- contracts the … cells of the …
- classic … reflex
- childbirth (…)
- in late pregnancy, uterine smooth muscle (…) becomes sensitive to …
- … feedback mechanism
- Breast-feeding
- contracts the myoepithelial cells of the alveoli
- classic neuroendocrine reflex
- childbirth (parturition)
- in late pregnancy, uterine smooth muscle (myometrium) becomes sensitive to oxytocin
- positive feedback mechanism

What mechanism is shown here?

Positive feedback mechanism
- Oxytocin is a … protein linked receptor
- causes … influx - causes contraction of smooth muscle in … or ….

Oxytocin is a G protein linked receptor
causes calcium influx - causes contraction of smooth muscle in endometrium or breast
Lesions of Hypothalamic Pituitary Axis
- Hypothalamic (hypothalamic or pituitary stalk disease) vs. primary pituitary disease
- … defects: Tumors (inc pit …), trauma, inflammatory/infiltrative, vascular (inc. Apoplexy) - most common
- … … defects: … syndrome, pituitary Aplasia, Anencephaly, Midline defects (rare)
- … Defects: Hypothalamic/Pituitary Hormone gene defects and hormone receptor gene defects (Very rare)
- Hypothalamic (hypothalamic or pituitary stalk disease) vs. primary pituitary disease
- Acquired defects: Tumors (inc pit adenomas), trauma, inflammatory/infiltrative, vascular (inc. Apoplexy)
- Congenital embryopathic defects: Killman’s syndrome, pituitary Aplasia, Anencephaly, Midline defects (rare)
- Genetic Defects: Hypothalamic/Pituitary Hormone gene defects and hormone receptor gene defects (Very rare)
Clinical Manifestations of Lesions of Hypothalamic Pituitary Axis - Tumours
- Mass effects include … and changes in … field leading to defects
- Endocrine effects:
- …pituitarism: TSH/ACTH/GH/LH-FSH/Prolactin
- …pituitarism: TSH/ACTH/GH/LH-FSH/Prolactin
- Mass effects include headaches and changes in visual field
- Endocrine effects:
- hypopituitarism:
- hyperpituitarism:
Syndrome of Panohypopituitarism
- progressive loss of … … function: first hormones to usually go = … and …, also …; …; …
- Hypopituitarism with … … is suggestive of hypothalamic etiology
- progressive loss of anterior pituitary function: first hormones to go = FSH/LH and GH; TSH; ACTH
- Hypopituitarism with Diabetes Insipidus is suggestive of hypothalamic etiology

What diagnosis is present in the image below?

Pituitary tumour

Prevalence of pituitary tumours: (6 types in total)
- What is most common?
- Second most common?
- What is relatively common? (2 types)
- least common?
- very rare?
- most common = prolactin tumours
- second most common = non-functioning tumors
- relatively common = GH tumours, ACTH tumors
- least common = FSH/LH
- Very rare = TSH tumors

Pituitary Adenoma
- Microadenomas are
- Macroadenomas are >and including …mm
- majority are monoclonal and not …
- may or may not be …
- … effects and … may be present irrespective of functional status
- Functioning (Secretes …) vs. non-functioning
- Microadenomas are <10mm
- Macroadenomas are >and including 10mm
- majority are monoclonal and not malignant
- may or may not be functional
- mass effects and hypopituitarism may be present irrespective of functional status
- functioning (Secretes hormones) vs. non-functioning
Types of Pituitary Adenoma
-
… : Produce too much prolactin
- Produces galactorreah, reduced … function
-
… secreting tumours: produce too much ACTH - too much cortisol = … syndrome
- centropetal …, … skin, osteoporosis, dia…
- … secreting: produce too much growth hormone - leading to …
- FSH/LH secreting: rare
- … syndromes
- TSHomas: TSH secreting - very rare
- leads to …
-
Prolactinomas: Produce too much prolactin
- Produces galactorreah, reduced gonodal function
-
ACTH secreting tumours: produce too much ACTH - too much cortisol = cushing’s syndrome
- centropetal obesity, thin skin, osteoporosis, diabetes
- GH secreting: produce too much growth hormone - acromegaly
- FSH/LH secreting: rare
- hypersecretion syndromes
- TSHomas: TSH secreting - very rare
- leads to thyrotoxicosis
Clinical Assessment - Pituitary
- … - symptoms of … excess or deficiency
- … - signs of hormone excess or deficiency
- basal hormone result - pituitary hormones e.g. …, ACTH, GH and downstream hormones e.g. …, IGF-1
- … secretion - to distinguish normal from abnormal
- … fields
- … MRI (CT)
- History - symptoms of hormone excess or deficiency
- examination - signs of hormone excess or deficiency
- basal hormone result s- pituitary hormones e.g. prolactin, ACTH, GH and downstream hormones e.g. cortisol, IGF-1
- Stimulated secretion - to distinguish normal from abnormal
- Visual fields
- Imaging e.g. MRI (CT - first way historically, MRI better)
Stimulating secretion results: Insulin Hypoglycaemia test
- Give …
- Blood glucose … - below … = pituitary churns out … to raise this level
- If you induce … episode = max response from pituitary, checks it’s ….
- Give insulin
- Blood glucose fall - below 2 = pituitary churns out hormones to raise this level
- If you induce hypoglycaemic episode = max response from pituitary, checks it’s response

Simultaneous Bilateral Inferior Petrosal Sinus and Peripheral Vein Sampling for ACTH
- 2 catheters into … supplying pituitary, either side
- give …. - cortisol releasing hormone
- Causes ACTH production from pituitary
- …. secreting adenoma = … release of ACTH
- See in figures if much brisker response on either side of the pituitary - shows what …. the tumour is on
- 2 catheters into vein supplying pituitary, either side
- give CRH - cortisol releasing hormone
- Causes ACTH production from pituitary
- ACTH secreting adenoma = greater release of ACTH
- See in figures if much brisker response on either side of the pituitary - shows what side the tumour is on

Pituitart Tumour Visual Field Defect
- Optic … - nerves cross above … - lesion pressing on this means you get a … …
- lose vision on …. of both eyes
- only place that causes this - characteristic of a pituitary tumour pressing on optic chiasm
- tells you exactly where lesion is
- Optic chiasm - nerves cross above pituitary - lesion pressing on this means you get a Bitemporal hemianopsia
- lose vision on outside of both eyes
- only place that causes this - characteristic of a pituitary tumour pressing on optic chiasm
- tells you exactly where lesion is

- What is shown in this image?

- CT scan of pituitary
What is shown in this image?

MRI of pituitary
What is shown in this image?

MRI of pituitary adenoma touching the optic chiasm