Hyperprolactinaemia Flashcards
What is hyperprolactinaemia?
The secretion of excess amounts of the hormone prolactin from the pituitary gland
What is the role of prolactin?
To stimulate lactation
It has a negative feedback effect on the gonadotropin releasing hormone (GnRH).
What are the resulting effects of hyperprolactinaemia on sex hormones?
Low levels due to an enhanced negative feedback
Where is prolactin produced?
Anterior pituitary
What hormone inhibits the release of prolactin?
Dopamine produced in the hypothalamus
What are the two pathophysiological causes of hyperprolactinaemia?
Excess production of prolactin from the pituitary
Disinhibition of dopamine
What are the three causes of dopamine disinhibition on prolactin?
Compression of the pituitary stalk
A reduction in dopamine levels
The use of a dopamine antagonist
What are the three physiological causes of hyperprolactinaemia?
Pregnancy
Lactation
Stress
What are the four pharmacological causes of hyperprolactinaemia?
Dopamine antagonists
Dopamine depleting drugs
Oestrogens
Antidepressants
What are the two dopamine antagonists which can cause hyperprolactinaemia?
Chlorpromazine
Metoclopramide
What are the four pathological causes of hyperprolactinaemia?
Hypothyroidism
Pituitary tumours, which secrete prolactin
Chronic renal disease
Polycystic ovary syndrome
What are the six signs and symptoms of hyperprolactinaemia?
Galactorrhoea
Amenorrhoea
Infertility
Bitemporal Hemaniopia
Erectile dysfunction
Gynaecomastia
What is galactorrhoea?
This is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing
What is amenorrhoea?
This is the absence of menstrual periods in a women during their reproductive years
Why is bitemporal hemianopia a symptom of hyperprolactinaemia?
Visual changes are experienced if the hyperprolactinaemia is associated with a pituitary gland tumour – as this can compress the optic chiasm
What three investigations are used to diagnose hyperprolactinaemia?
Prolactin blood test
Prolactin stimulation test
MRI scan
How do we carry out a prolactin blood test?
This blood test requires a venepuncture, which is the puncture of a vein to withdraw blood
This test must be carried out between 9am and 4pm
What is the normal level of prolactin?
Less than 20ng/mL
What prolactin level indicates hyperprolactinaemia?
25ng/mL (550mu/l)
What is a prolactin stimulation test?
A prolactin stimulation test involves injecting patients with metoclopramide, which is a drug involved in controlling prolactin levels. Specifically, it is a dopamine antagonist that exerts inhibition on prolactin secretion
How does a prolactin stimulation test affect normal patients?
It results in increased levels of prolactin and a small increase in TSH levels
How does a prolactin stimulation test affect those with microprolactinoma?
Metoclopramide will result in a marked increase in TSH levels, however there is no effect on the prolactin levels
How does a prolactin stimualtion test affect those with macroprolactinoma?
Metoclopramide will result in no effect on either the TSH levels or the prolactin levels
How is an MRI scan used to diagnose hyperprolactinaemia?
An MRI scan of the pituitary gland is used to exclude any other pituitary gland abnormalities that may be responsible for the symptoms – such as a pituitary tumour
