Hypopituitarism Flashcards
Anterior pituitary hormones
Growth hormone
Prolactin
LH and FSH
Thyroid stimulating hormone
adrenocorticotrophic hormone
What’s the anterior pituitary blood supply called
Hypophyseal portal system
effects of each of the anterior pituitary hormones?
GH: growth, LH/FSH: testosterone/estrogen & progesterone, prolactin: milk production, ACTH: cortisol secretion, TSH: T3/T4 secretion
is a failure of the affected gland itself considered primary or secondary failure?
Considered primary
Pituitary failure is secondary
Hypothalamus is tertiary
Difference in TSH level between primary/secondary hypothyroidism
TSH is high in primary and low in secondary
name each of the pituitary hormone stimulators from the hypothalamus
GH: GHRH (growth hormone releasing hormone), FSH/LH: GnRH (gonadotropin releasing hormone), TSH: TRH (thyrotropin releasing hormone), prolactin: no direct one, ACTH: CRH (corticotropin releasing hormone)
How’s prolactin controlled
Inhibited by dopamine release
Congenital hypopituitarism
Rare cause by mutation of transcription factor genes needed for normal anterior pituitary development
Need to be deficient in GH and one other hormone
Short stature and hypoplastic anterior pituitary gland on mri
Panhypopituitarism
Total loss of anterior and posterior pituitary function
Examples of causes include pituitary tumour,trauma,radiation,infection
Inflammation (hypophysitis) or surgery.causes it
which hormones are most sensitive to radiotherapy?
GH and gonadotrophin
why is annual assessment required for pituitary radiation damage?
risks from radiotherapy persist for up to 10 years after dose
What’s sheehans syndrome
peripartum infarction of pituitary —> hypopituitarism
Caused by hypotension a common cause of which is postpartum haemorrage
Have lethargy weight loss TSH/ACTH/GH deficiency
Failure of lactation
Failure to resume menses
why does hypotension lead to pituitary infarction?
pituitary gland becomes enlarged during pregnancy (lactotroph hyperplasia)but the blood supply does not increase to compensate meaning it is at high risk of becoming hypoxic
Post partum haemorrage leads to pituitary infarction
why is the posterior pituitary not usually affected?
Separate blood supply not reliant on portal system
Best radiological way to visualize pituitary
MRI
What’s pituitary apoplexy
haemorrhage into pituitary, usually dramatic in patients with pre-existing pituitary adenoma.
Can be precipitated by anticoagulants
May be first presentation of pituitary adenoma
some symptoms of pituitary apoplexy:
sudden onset headache, vision impairment e.g. bitemporal hemianopia, diplopia (double vision), ptosis (upper eyelid drooping) due to cranial nerve involvement ( cavernous sinus involvement)
How to measure ACTH and GH
give insulin to induce hypoglycemia (stress) then measure GH/cortisol
Can’t do in elderly patients or if you have heart disease
Empty sella
Thin empty layer of pituitary tissue caused by previous presence of an adenoma
how to treat GH deficiency?
assess quality of life w questionnaire, daily injections. response measured by QoL up, serum IGF-1 up
how to treat TSH deficiency?
replace with levothyroxine and adjust dosage based on fT4 (not TSH as you would with primary hypothyroidism)
how to treat ACTH deficiency?
replace cortisol not ACTH. diurnal variation mimicked by either prednisolone once daily AM or hydrocortisone 3x per day e.g. 10mg 5mg 5mg
what is an adrenal crisis and what causes it?
triggered by intercurrent illness, features include vomiting, dizziness, collapse, death
sick day rules for steroid dependent patients (ACTH/adrenal gland dysfunction):
double steroid dose (glucocorticoid not mineralcorticoid), wear alert bracelet, come A&E if unable to take tablets
- how to treat FSH/LH deficiency in men?
no fertility needed: testosterone replacement IM injection or topical. (doesn’t restore spermatogenesis as that’s dependent on LH/FSH)
fertility needed: induce spermatogenesis (depends on FSH) by injections. may take 6-12 months.
How to treat FSH/LH deficiency in women
Replace oestrogen with additional progesterone if uterus intact to prevent endometrial hyperplasia
fertility required: time gonadotropin injections to induce ovulation
which anterior pituitary axis doesn’t need hormone replacement?
Prolactin
Presentations of hypopituitarism
FSH/LH causes reduced libido secondary amenorrhea erectile dysfunction reduced pubic hair
ACTH and TSH fatigue
GH causes reduced quality of life or short stature in children
PRL causes inability to breastfeed
Acquired causes of hypopituitarism
Tumours eg adenomas metastases and cysts
Radiation eg hypothalamic/pituitary
Infection eg meningitis
Traumatic brain injury
Pituitary surgery
Inflammatory (hypophysitis)
Pituitary apoplexy haemorrage
Peri partum infarction-Sheehans syndrome
Biochemical diagnosis of hypopituitarism
Cortisol early morning
Thyroxine T4 circulating 6 days
FSH LH cyclical in women
GH and ACTH is pulsatile
