Hypersecretion of anterior pituitary hormones Flashcards
What is a common feature of hypersecretion of anterior pituitary hormones
Usually just one type of hormone- not the whole gland
Summarise hyperpituitarism
Symptoms associated with excess production of adenohypophysial hormones
Usually due to isolated pituitary tumours but can also be ectopic (i.e. from non-endocrine tissue) in origin
can quite often be associated with visual field and other (e.g. cranial nerve) defects
as well as endocrine-related signs and symptoms
What is meant by an ectopic cause
Neuroendocrine tumours- densely packed tumour full of peptide hormones- similar to peptide hormones
Carcinoid tumours of the gut can release too much ACTH- Cushing’s- but the pituitary gland is itself fine.
Why are both eyes affected by bitemporal hemianopia
o Both eyes may be affected by bitemporal hemianopia as the decussation of nerves is at the optic chiasm (where the pituitary is)
Describe the optic chiasm
At the optic chiasm, fibres from the nasal retinae cross. Light from the outer (temporal) aspects of the visual fields strikes the nasal aspect of the retina. Hence compression (by growth of a suprasellar tumour) of these crossing fibres at the optic chiasm means that there is loss of vision from the outer temporal visual fields.
Describe perimetry
Look straight ahead- look at screen with flashes and press button when you see the flashes- normal person can see all the flashes- no black.
However, a person with bitemporal hemianopia may not be able to see all of the flashes- some black spots
Describe what the consequences of excesses in each hormone
ACTH (corticotrophin) à Cushing’s disease.
TSH (thyrotrophin) à Thyrotoxicosis.
LH, FSH (gonadotrophins) à Precocious puberty in children.
Prolactin à Hyperprolactinaemia.
GH à Gigantism, Acromegaly.
What is the usual cause of hypersecretion of anterior pituitary hormones?
Pituitary adenoma
Differentiate between the pathological and physiological causes of hyperprolactinaemia
Physiological pregnancy breastfeeding Pathological prolactinoma (often microadenomas < 10mm diameter)
What happens to GnRH pulsatility during puberty
Becomes much more frequent and much more rapid
List the symptoms of hyperprolactinaemia due to a prolactinoma seen in females
galactorrhoea (milk production)
secondary amenorrhoea (or oligomenorrhoea)- often the presenting complaint and why picked up earlier in women- due to lack of FSH and LH
loss of libido
infertility
List the symptoms of hyperprolactinaemia due to a prolactinoma seen in males
galactorrhoea uncommon (since appropriate steroid background usually inadequate) loss of libido erectile dysfunction infertility
Can men with prolactinomas present with galactorrhoea
Galactorrhoea occurs in oestrogen-primed breasts
Generally, men don’t have enough oestrogen to be able to lactate
However, some men with breast hypertrophy (gynaecomastia) complain of milk production
Differentiate between loss of libido and impotence
Loss of libido-due to low testosterone
Lack of testosterone causes a lack of sexual drive, which is unlike the impotence which is seen in diabetes for example.
In the latter case, diabetic patients have a normal sex drive (libido), but seek medical attention for their erectile dysfunction (impotence) usually due to associated cardiovascular problems.
How do prolactinomas often present in male patients
In the male with a prolactinoma, the patient does not perceive any problem at all, and occasionally a spouse might complain about ‘lack of interest’ and encourage referral, or eventually the patient presents with a large prolactinoma and features of hypopituitarism .
What is a consequence of a difference in timings of the presentation of prolactinomas in males and females
Female patients- often see microprolactinomas
Male patients - often see macroprolactinomas
Probably true only because we fail to diagnose the males when their tumours are small.
Summarise the pathophysiology of treatment for prolactinomas
Dopamine from dopaminergic neurones binds to D2 receptors on the lactotrophs and switches OFF prolactin secretion.
Will reduce the size of the tumour too- only tumour tat can be managed medically (without surgery)
What are D3 receptors involved in
The reward system in the brain.
Summarise the treatment of hyperprolactinaemia
Medical treatment is 1st line Dopamine receptor (D2) agonists Decrease prolactin secretion Reduce tumour size Examples: BROMOCRIPTINE CABERGOLINE Oral administration
What should we do when the tumour does not shrink whilst being treated with dopamine agonists
If the tumour does not shrink, it is important to reconsider the diagnosis, as it is possible that the patient always had disconnection hyperprolactinaemia , and this differential diagnosis is difficult to confim
State the side effects of dopamine receptor agonists
Nausea and vomiting
Postural hypotension
Dyskinesias (loss of voluntary movement)
Depression (exhaustion of dopamine stores)
Pathological gambling (see BNF!)- dopamine receptors are part of the reward system (D3)- some of these are activated- need someone who knows the patient well to monitor them- individual will have no insight on this.
What should be done in patients who cannot tolerate dopamine receptor agonists
i.e those with schizophrenia are made much worse by dopamine agonists, surgery and/or radiotherapy are options to be considered
Essentially, how do we diagnose prolactinomas
The combination of a raised circulating prolactin level with a visible prolactin tumour on the MRI scan suggests that there is a prolactinoma but it is essential that the diagnoses of disconnection hyperprolactinaemia or other causes of hyperprolactinaemia are excluded. The size of the tumour and the relative height might be useful. For example, a prolactin level over 6000 mU.L-1 can only be due to a prolactinoma. Levels between 1000 and 6000 mU L-1 are more difficult to interpret, and can be due to a small macroprolactinoma, or to a large tumour causing disconnection from the hypothalamus- patients should be reviewed by MDT
Compare the effects of excess growth hormone in humans and in adults
§ Childhood = gigantism. Adulthood = acromegaly.
§ Usually due to BENIGN GH secreting pituitary adenoma (of the somatotrophs)
Why don’t we see gigantism in adults
The epiphyses of long bones have fused, therefore linear growth is unlikely but other tissues undergo hypertrophy where possible, and a very stereotypic appearance occurs. Prognathic Jaw Frontal Bossing Spade Hands Wide spaced teeth
