Hypopituitarism Flashcards
What hormones are found in the anterior pituitary and what is their role?
Growth hormone- growth Prolactin- milk production Thyroid stimulating hormone- T3 and T4 LH and FSH- oestrogen and progesterone Adrenocorticotropic hormone- cortisol
What is the hypothalamo-pituitary system?
Hypothalamic releasing or inhibitory factors travel own the portal circulation to the anterior pituitary to regulate anterior pituitary hormone function
What can anterior pituitary failure affect?
Thyroid
Adrenal Cortex
Gonads
Can fail due to primary disease (gland fails) or secondary disease (no signal from hypo or ant. pituitary)
What are the consequences of primary hypothyroidism?
E.g. autoimmune destruction of thyroid gland
T3 and T4 fall but TSH increases
What are the consequences secondary hypothyroidism?
E.g. pituitary tumour damaging thyrotrophs
Cant make TSH
TSH falls
T3 and T4 fall
What are the consequences of primary hypoadrenalism?
E.g. destruction of adrenal cortex
Cortisol falls
ACTH increases
What are the consequences of secondary hypoadrenalism?
E.g. pituitary tumour damaging corticotrophs
Can’t make ACTH
ACTH falls
Cortisol falls
What are the consequences of primary hypogonadism?
E.g. destruction of testes or ovaries
Testosterone/ oestrogen fall
LH and FSH increase
What are the consequences of secondary hypogonadism?
E.g. pituitary tumor damaging gonadotrophs
Can’t make LH/FSH
LH and FSH fall
Oestrogen and testosterone fall
What are causes of hypopituitarism?
Congenital:
Rare and usually due to mutations of transcription factor genes needed for normal anterior pituitary development
What is an example of a congenital cause of hypopituitarism?
PROP1 mutation
Deficient in GH and at least 1 more anterior pituitary hormone
Short stature
Hypoplastic anterior pituitary gland on MRI
What are acquired causes of hypopituitarism?
Tumours eg adenomas, metastases, cysts
• Radiation (hypothalamic/pituitary damage)
• Infection eg meningitis
• Traumatic brain injury
• Pituitary surgery
• Inflammatory (hypophysitis)
• Pituitary apoplexy - haemorrhage (or less
commonly infarction)
• Peri-partum infarction (Sheehan’s syndrome)
What do we call total loss of anterior and posterior pituitary function?
Panhypopituitarism
How can radiotherapy induce hypopituitarism?
Pituitary and hypothalamus are both sensitive to radiation
GH and gonadotrophs are most sensitive
PRL (prolactin) can increase after radiotherapy (loss of hypothalamic dopamine)
Risk persists up to 10 years after radiotherapy so annual assessment required
How does hypopituitarism present?
FSH/LH: Reduced libido Secondary amenorrhoea Erectile dysfunction Reduced pubic hair
ACTH:
Fatigue
NB Not a salt losing crisis (reninangiotensin)
TSH:
Fatigue
GH:
Reduced quality of life
NB short stature only in children
PRL:
Inability to breastfeed
What is sheehan’s syndrome?
Postpartum hypopituitarism secondary to hypotension (due to postpartum haemorrhage) It's more common in developing countries Anterior pituitary enlarges in pregnancy (lactotroph hyperplasia) PPH leads to pituitary infarction
What are symptoms of sheehan’s syndrome?
• Lethargy, anorexia, weight loss – TSH/ACTH/(GH) deficiency • Failure of lactation – PRL deficiency • Failure to resume menses post-delivery • Posterior pituitary usually not affected
What is pituitary apoplexy?
Intra-pituitary haemorrhage or (less commonly) infarction (obstruction of blood)
There’s often a dramatic presentation in patients with pre-existing pituitary tumours
It may be the first presentation of pituitary adenoma
Can be caused by anticoagulants
What are symptoms of a pituitary apoplexy?
• Severe sudden onset headache
• Visual field defect – compressed optic chiasm,
bitemporal hemianopia
• Cavernous sinus involvement may lead to
diplopia (IV, VI), ptosis (III)
How is hypopituitarism diagnosed?
You need to take caution when looking at basal plasma hormone concentrations:
- Cortisol – what time of day?
- T4 – circulating t1/2 6 days (half life)
- FSH/LH – cyclical in women
- GH/ACTH - pulsatile
How would you measure ACTH and GH hormones?
These are pulsaile so you have to take dynamic measurements
Since ACTH and GH are stress hormones we can induce stress by making the patients hypoglycaemic- this releases GH and ACTH
How would I stimulate TSH and FSH/LH release?
TRH stimulates TSH release
GnRH stimulates FSH & LH release
What hormone can we not restore in hypopituitarism?
Prolactin
How is GH deficiency treated?
You would confirm GH on a dynamic pituitary function test
You would then assess the quality of life using a specific questionnaire
If low QoL, prescribe daily injection
Measure response by
• improvement in QoL
• plasma IGF-1
