2 - Hypersecretion of anterior pituitary hormones Flashcards
(27 cards)
What is the usual cause of hypersecretion of anterior pituitary hormones?
Pituitary adenoma
usually benign tumours but can cause problems physically by pushing on the anterior pituitary
Give some other causes of hypersecretion of anterior pituitary hormones?
(can be ectopic in origin) - non-endocrine tissue (neuroendocrine)
e.g. vasopressin producing lung tumours
What is a common defect that comes with hypersecretion of anterior pituitary hormones that is not directly caused by the hyper secretion?
How are these caused?
visual field defects
the tumour can have an effect on structures that are close to the pituitary (optic chaism may be squashed by a tumour)
What visual defect is associated with pituitary adenoma?
Bitemporal hemianopia
State the disease resulting from hypersecretion of:
a. Cortictrophin
b. Thyrotrophin (rare)
c. Gonadotrophins
d. Prolactin
e. Somatotrophin (GH)
a. Cushing’s disease
b. Thyrotoxicosis
c. Precocious puberty in children
d. Hyperprolactinaemia
e. Gigantism/Acromegaly
What is the usual cause of hyperprolactinaemia?
Prolactinoma
Most commonly microadenomas (< 10 mm)
How is prolactin secretion regulated?
(lactotrophs produce prolactin)
- regulated by dopamine (from hypothalamic dopaminergic neurones)
- under constant inhibition by dopamine
- dopamine binds to D2 receptors on lactotrophs
(this suppresses prolactin)
How can hyperprolactinaemia be treated?
surgery is not the first line of treatment
DOPAMINE RECEPTOR AGONIST
Give the drug name that is used to treat hyperprolactinaemia?
cabergoline (or bromocriptine)
What are the side effects of dopamine receptor agonists?
nausea and vomiting postural hypotension dyskinesias DEPRESSION pathological gambling
State two physiological causes of hyperprolactinaemia.
Pregnancy
Breast feeding
What does excess growth hormone cause in children and in adults?
Children – gigantism
Adults – acromegaly
What is excess of somatotrophin usually due to?
a benign growth hormone secreting pituitary adenoma
not cancerous, but physically disturbs the pituitary
What are the most serious complications of excess growth hormone?
Cardiovascular problems (majority) and respiratory problems This is mainly due to organ growth
State some common clinical manifestations of acromegaly.
Prognathism Enlarged supraorbital ridges Enlarged soft tissue Hyperhydrosis Carpal tunnel syndrome (due to excessive cartilaginous growth) General coarseness of features Hypertension Headache (cardinal feature)
What are the metabolic effects of acromegaly?
Increased insulin response to oral glucose leading to insulin resistance
This causes impaired glucose tolerance (in 50%) and diabetes mellitus (in 10%)
What are the other complications that can arise from acromegaly?
- obstructive sleep apnoea
- hypertension
- cardiomyopathy
- increased risk of cancer
- diabetes (metabolic)
What type of test is used to diagnose a hyperpituitary disorder?
Suppression test
What test is used to diagnose acromegaly and how are the results interpreted?
Glucose-induced suppression of growth hormone secretion
Giving glucose should cause a decrease in growth hormone release in a normal individual
In someone with acromegaly, giving glucose will cause a PARADOXICAL rise in growth hormone release
State some of the treatments for acromegaly.
• SURGERY - Transsphenoidal Hypophysectomy
• Radiotherapy (may become hypopituitary)
• Chemotherapy: (used in prep for surgery)
—–> somatostatin analogue (Octreotide)
—–> dopamine receptor agonists (Bromocriptine and Cabergoline)
What is ocreotide? What type of drug is it? What is it used to treat?
a somatostatin analogue
used to treat acromegaly (excess of growth hormone)
NOTE: it inhibits lots of peptides and isn’t specific to just GH
What are the clinical uses of octreotide? (when is it used?
It can be used short-term before surgery to shrink the size of the pituitary adenoma
It can be used long-term if it can’t be controlled by other means
It is used as a treatment for other neuroendocrine tumours e.g. carcinoid tumours
State some of the side effects of octreotide.
GI tract disturbance (because somatostatin is produced by the small intestine as well) - nausea, diarrhoea, rarely gallstones
Initial reduction in insulin secretion causing hyperglycaemia (octreotide inhibits the production of insulin by the beta cells)
Describe which neurones cross over at the optic chiasm
fibres from the nasal part of the retina cross over
the temporal hemiretina stay on the same side
