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what projects signals to posterior pituitary?

magnocellular neurons in hypothalamus

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Pituitary cells?

Somatatrophs : somatostatin , growth hormones

corticotrophs; Adrenocorticotropic hormone

lactotrophs : prolactin

thyrothrophs: TSH
gonadotrophs: FSH,LH

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primary hypothyroidism?

defect in the gland - autoimmune

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secondary hypothyroidism

disorder of thyrotrophs - anterior pituitary

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why is anterior piuitary more susceptible to sheehans ?

the blood supply to anterior-pituitary is at increased risk of damage because it is supplied mainly by long hypophyseal vessels and portal capillaries in pituitary stalk and blood supply to posterior gland is less susceptible to damage as it is supplied by short hypophyseal vessels.

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Pituitary apoplexy

is severe bleeding in or loss of blood flow to the pituitary gland

associated with pituitary blood supply

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presentation

of Pituitary apoplexy

Severe sudden onset headache
Visual field defect – bitemporal hemianopia, diplopia, ptosis
↓ Secretion of hormones

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how does hypopituitarism present - fsh/lh impacts ?

reduced libido
secondary amenorrhoea
Erectile dysfunction
Reduced pubic hair

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Presentation of Hypopituitarism

ACTH

ACTH
Fatigue
NB Not a salt losing crisis (renin-angiotensin)

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Presentation of Hypopituitarism TSH

PRL

Reduced quality of life
NB short stature only in children

fatigue

Inability to breastfeed

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why are MRI preferred for imaging the pituitary?

Pituitary MRI (CT not so good at delineating pituitary gland)

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Biochemical markers for hypopituitarism

[basal plasma]
T4 - long half life about 3 months

fsh/Lh - cyclical

Gh/ACTH - pulsatile

take with caution as variable

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functioning pituitary tumours

prolactinoma
acromegaly
cushings disease

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Presentation of Prolactinoma

Lactotroph pituitary adenoma galactorrhea
fatigue
erectile dysfunction

reduced libido
impacts menstrual cycle
subfertility

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why does having a prolactinoma impact sex?

reduced libido, erectile dysfunction and vaginal dryness
impotence

due to prolactin reducing FSH/LH production - so decreased oestrogen and testosterone = low sperm count and ovulation
inhibition of kisspeptin neuron

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treatment for Prolactinoma?

Dopamine receptor agonist, e.g. BROMOCRIPTINE, CABERGOLINE

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why are dopamine receptor agonist used to treat Prolactinoma?

physiologically dopamine binds to d2 receptors on anterior pituitary lactotrophs and inhibits prolactin release; so dopamine receptor agonist do the same thing and eventually shrink the tumour

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acromegaly

presentation

physical signs

complaints

excess growth hormone
somatotrophs

=overgrowth : tongue,nose,jaw,hand/feet size

Bi-temporal hemianopia
headaches
excessive sweating

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diagnosis of Acromegaly

serum IGF-1 raised

oral glucose tolerance test

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why is a glucose test done on someone with suspected acromegaly?

GH is a stress hormone so is released in response to low glucose in blood

if glucose is given and there is no suppression of GH that is abnormality

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why is IGF-1 measure not GH? What is IGF-1?

insulin like growth factor 1

when GH travels to liver- produces IGF-1 so a good serum marker to see release of GH

GH itself is pulsatile so not useful to measure randomly

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treatment of acromegaly?

CVd risk so need to treat

transphenoidal surgery
Inhibition of GH release by somatostatin analogues
dopamine agonists: expression of dopamine receptors on these tumours mean gd target and dopamine inhibits GH

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Cushing Disease

excess cortisol
- too much ACTH

proximal myopathy 
depression 
High BP
diabetes 
osteoporosis

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diagnosis of Cushing

Study These Flashcards

24h urine free cortisol test will show continually elevated cortisol, high late night cortisol

oral DEXAMETHASONE : cortisol still not suppressed

why is oral dexamethasone given to test for cushing?

oral dexamethasone acts like a synthetic cortisol so should cause suppression of cortisol release from adrenal cortex but in someone with hypercortisolism it wont be suppressed

non -functioning pit adenoma

bitemporal hemianopia | compression of optic chiasm

ADh promotes water reabsoroption from where?

renal collecting ducts via V2 receptors

Stimuli for vasopressin release are: | ______sensed by ______ in the hypothalamus ; Process: ______are special neurons in the hypothalamus that sense _____

- increased plasma osmolality (concentration) - osmoreceptors - osmoreceptors - plasma osmolality

Diabetes insipidus | polyuria, nocturia & polydipsia

inability to make vasopressin

Desmopressin test

Desmopressin is a synthetic VP so if cranial - giving DDAVP would concentrate urine and increase water reabsorption if nephrogenic -rarer- no response to DDAVP

how to treat nephrogenic cranial DI?

- thiazide diuretics | - desmopressin

if someone has a low urine osmolality after DDAVP administration what does it mean?

low urine osmolality means urine is not concentrated = Lots of water loss if no response to DDAVP then it means they have Nephrogenic diabetes insipidus

SIADH?

Syndrome of inappropriate antidiuretic hormone secretion

SIADH pathophysiology and presentation?

too much adh > water reabsorption [alot] > blood volume is HIGH hypervolemic > sodium loss?? hyponatraemia

other actions of Vasopressin?

vasoconstrictor - V1 receptor | stim ACTH release anterior pituitary

non osmotic stimuli for ADH?

Decrease in atrial pressure sensed by atrial stretch receptors

why can nuclei of posterior pituitary respond to systemic circulatory changes? [osmoreceptors- 3rd ventricle]

no blood brain barrier

why is the non osmotic stimuli for ADh important? such as reduction in circulating volume

restore blood volume in case of haemorrhage by increasing water reabsorption vasoconstriction via v1 receptors also

cause of Nephrogenic diabetes

genetic : mutated V2, aquoporin 2 drugs : lithium

management of SIADH?

Fluid restriction | Vaptan (vasopressin antagonist (binds to v2 receptors))

causes of SIADH

``` CNS - Head injury, stroke, tumour, Pulmonary disease - Pneumonia, bronchiectasis Malignancy - Lung cancer (small cell) Drug-related - Carbamazepine, - Serotonin Reuptake Inhibitors (SSSRIs) Idiopathic ```

management of hyperthyroidism | drugs

First 3 drugs reduce thyroid hormone synthesis β blockers help with symptoms Thionamides 🡪 inhibit thyroid peroxidase and hence inhibit T3/T4 synthesis B-blockers e.g. propranolol reduce tremor, tachycardia Potassium iodine inhibits

how does potassium iodine work?

fills up thyroid with stable iodine so radioactive iodine cannot be taken up - reduces T4/T3 production

radioiodine moa? | what is it used for?

Hyperthyroidism destroys cells in thyroid gland = reduces thyroxine levels and size of gland radiation destroys the overactive cells

Cushing diagnosis?

24hr urine free cortisol blood diurnal levels low dose dexamethasone suppression test > dexamethasone acts like cortisol so upon administration normal physiological response would be for serum cortisol to go down- failure to suppress= cushing

what tumour can cause cushings syndrome?

ectopic ACTH lung cancer adrenal adenoma secreting cortisol pituitary tumour - Cushing disease

High acth

cushings disease

low ACTH : cushings syndrome?

steroid medication | adrenal adenoma

Ketoconazole = antifungal; risk of hepatotoxicity (possibly fatal liver damage) so use is not advised but it is still prescribed. Mainly blocks 17α hydroxylase, inhibiting cortisol production. control of cushings syndrome prior to surgery

= antifungal; risk of hepatotoxicity (possibly fatal liver damage) so use is not advised but it is still prescribed. Mainly blocks 17α hydroxylase, inhibiting cortisol production. control of cushings syndrome prior to surgery

Metryrapone

Metryrapone = inhibition of 11β-hydroxylase; steroid synthesis in the zona fasciculata [and reticularis] is arrested at the 11-deoxycortisol stage

Conns syndrome

benign adrenal corticol tumour = ALDOSTERONE secretions increased

which condition increases aldosterone secretion?

Conns | Primary aldosteronism

treatment for Conns ?

Competitive Mineralocorticoid antagonists Spironolactone Epleronone blocks aldosterone from binding

phaeochromocytoma hyperadrenalism of what? what part of adrenal gland?

XS catecholamines adrenaline/noradrenaline medulla

Symptoms | of phaeo?

``` palpitations headache sweating chest pains, nausea, tremor, anxiety, hypertension, pallor, tachycardia, fever, weight loss ``` due to stimulates alpha and beta adrenergic receptors

what heart condition can Phaeo lead to?

Hypertension > MI/Stroke ventricular fibrillation = death

management of Phaeo

Alpha blockade IV fluids Beta blockade Surgery to remove tumour

Hypoadrenalism?

Addisons | Congenital adrenal hyperplasia

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