16. Pituitary Disorders Flashcards
What is the clinical presentation of pituitary tumours?
Mass effect of tumour on local structures - visual loss, headache
Abnormality in pituitary function - hypo or hyper secretion
Why is there visual field loss in upwards growth of pituitary tumour?
Pressure on optic chiasm
Causes bitemporal hemi-anopia (tunnel vision)
What does lateral growth of pituitary tumour cause?
Pain and double vision
What is the order of hormone secretion lost from a pituitary tumour?
Growth hormone
Gonadotropin hormone
TSH and ACTH
What does a gonadotropin deficiency cause?
Delayed puberty in children
Loss of secondary sexual characteristics in adults
Loss of periods an early sign in women
What does TSH deficiency cause?
Low thyroid hormones Weight gain Tiredness Slow pulse Low T4 and non-elevated TSH
What does a ACTH deficiency cause?
Low cortisol Tired Dizzy Low BP Low sodium Can be life-threatening
What are the most common abnormalities in pituitary function and hormone excess?
Prolactin
GH
ACTH
How do you do a biochemical assessment of pituitary diseases in thyroid, gonadal and prolactin axes?
Basal blood test sufficient
Thyroid axis - fT4, TSH
Gonadal axis - LH, FSH, testosterone, oestradiol
Prolactin axis - serum prolactin
How do you do a biochemical assessment of pituitary disease in the HPA and GH axes?
Dynamic blood test
HPA axis - cortisol at 9am
GH axis - GH/IGF-1
If a deficiency is suspected in the adrenal axis what would you do?
Synacthen test - direct stimulation of adrenals by ACTH
Insulin stress test - response to hypoglycaemic stress
If an excess in the adrenal axis is suspected what do you do?
Dexamethasone suppression test - suppress ACTH axis with steroids
If a deficiency is suspected in GH axis what do you do?
Insulin stress test - response too hypoglycaemic stress
If an excess in GH axis is suspected what do you do?
Glucose tolerance test - suppress GH axis with glucose load
What is a prolactinoma?
Prolactin-secreting pituitary tumour
The larger the tumour, the higher the prolactin
How are prolactinomas treated?
With tablets, never operation
What are symptoms of hyperprolactinaemia in women?
Menstrual disturbance
Fertility problems
Galactorrhoea - milk discharge from nipple
What are the symptoms of hyerprolactinaemia in men?
Present later than women
Usually larger tumours
Symptoms of low testosterone are non-specific
May present with mass symptoms such as visual loss
How are high prolactin and pituitary mass connected?
Prolactin is under tonic inhibitory control by dopamine
Anything blocking stalk will lead to prolactin disinhibition
If prolactin <5000 high prolactin may be due to disinhibition
If prolactin >5000 high prolactin likely to be due to active prolactin secretion
What are non-functioning pituitary adenomas?
No secretion of biologically active hormones
May secrete inactive hormones (ACTH or LH/FSH)
Clinical features due to mass effect or symptoms of low pituitary hormones
What is the treatment of prolactinoma?
Dopamine agonists stimulate D2 receptor
Bromocriptine and cabergoline reduce prolactin
Dopamine antagonists can cause high prolactin, such as drugs for anti-sickness or anti-psychotic
What is acromegaly caused by?
GH secreting pituitary tumour
Leading to gradual changed in features over years
What are the long-term complications of untreated acromegaly?
Premature cardiovascular death
Increased risk of colonic tumours
Probably increased risk of thyroid cancer
Disfiguring body changes that may be irreversible
Hypertension and diabetes
What are the biochemical tests to confirm acromegaly?
Oral glucose tolerance test with GH response
Failure to suppress GH
Elevated IGF-1 level
Growth hormone day curve - elevated mean GH
