2) Hypersecretion of APG hormones Flashcards
What is the most common cause of hyperpituitarism?
Tumours
- pitutary
- ectopic-from non-endocrine tissue elsewhere in body
What is hyperpituitarism commonly linked to?
Bitemporal hemniaopia
- PG compresses optic chiasm
- loss of peripheral vision + headache
What does an excess of each APG hormone cause?
Excess ACTH=Cushing's syndrome Excess TSH=Thyrotoxicosis Excess LH/FSH=precocious puberty Excess prolactin=Hyperprolactinaemia Excess GH=gigantism/acromegaly
How is prolactin release normally controlled?
Inhibitory regulation by dopamine
Where is prolactin normally secreted from?
lactotrophs in APG
Physiological reasons prolactin levels may be high?
Pregnancy
Breast feeding
Pathological reasons prolactin levels may be high?
Prolactinoma (pituitary adenoma)
What can hyperprolactinaemia cause?
Loss of libido
Secondary amenorrhoea
Erectile dysfunction
Galacttorhoea (women)
What is the link between hyperprolactinaemia with FSH/LH?
High levels of prolactin suppress GnRH pulsatility which reduces LH/FSH levels
How is hyperprolactinaemia treated?
D2 receptor antagonist e.g. bromocriptine/cabergoline to mimic dopamine suppression of prolactin release
3 Side effects of D2 receptor agonists?
Pathological gambling
Postural hypotension
Nausea/vomiting
What cells in the APG secrete GH?
Somatotrophs
What is GH excess called in children vs adults?
Children=gigantism
Adults=acromegaly
What is the main cause of GH excess?
Pituitary adenoma-somatotrophs
What type of tissue grows more in acromegaly?
Soft tissue
What type of onset does acromegaly have?
Slow
2 hallmark signs of acromegaly & what do they indicate?
Sweating
Headache
Indicate active disease
List clinical features of acromegaly:
Sweating
Headache
Barrel chest Coarsness of facial features Mandible grows-lower jaw protrusion Spaceshaped hands Macroglossia Carpel tunnel syndrome Bitemporal hemniopia
5 possible complications of acromegaly
Diabetes mellitus-GH is a stress hormone so tries to increase BGC Obstructive sleep apnoea Hypertension Cardiomyopathy Increased cancer risk
Acromegaly treatment:
Surgery
Radiotherapy
Somatostatin analogues
D2R agonists-many GH tumours express D2R
What is the link between acromegaly + prolactin?
GH tumours often co-secrete prolactin
How is acromegaly diagnosed?
1) Elevated IGF-1
2) OGTT-paradoxical GH rise after glucose given
Why can’t we simply measure GH levels to diagnose acromegaly?
GH release is pulsatile
What normally happens to GH when glucose increases vs what happens in acromegaly?
GH=stress hormone which tries to increase BGC
Normal-increased glucose reduced GH production
Acromegaly-GH increases with glucose (PARADOXICAL)
Why might someone with acromegaly have glucose in their urine?
Excess GH increases glucose production=renal threshold exceeded
