Hypersecretion of Anterior Pituitary Hormones

Question 1

What is hyperpituitarism often associated with?

Answer 1

usually due to isolated pituitary tumours but can also be ectopic

often associated with visual field defects due to close proximity to optic chiasm - bitemporal heminopia

Question 2

What does an excess of each hormone lead to?

Answer 2

ACTH - Chushing's disease
TSH - thyrotoxicosis
LH.FSH - precosious puberty in children
prolactin - hyperprolactinaemia
GH - gigantism/acromegaly

Question 3

What are the causes if hyperproalctinaemia?

Answer 3

physiological - pregnancy, breast feeding
patholphyisiological - prolactinoma ( most common functioning pituitary hormone - high prolactin suppresses GnRH pulsatility

Question 4

What are the signs and symptoms of hyperprolactinaemia?

Answer 4

women - galactorrhoea, secondary amenorrhoea/ oligomenorrhoea, loss of libido, infertility

men - galactorrhoea uncommon, loss of libido, erectile dysfunction, infertility

Question 5

What is the treatment for hyperprolactinaemia?

Answer 5

D2 recepetor agonists - inhibit prolactin release.
This medical treatment (orally) is 1st line (i.e. surgery is NOT first line).
D2 agonists then - decrease prolactin secretion and reduce the tumour size.

Side effects include – nausea/emesis, postural hypotension, dyskinesia (loss of voluntary movement), depression (exhaustion of dopamine stores), pathological gambling.

EXAMPLES: BROMOCRIPTINE, CABERGOLINE.

Question 6

What is the difference between gigantism and acromegaly?

Answer 6

Childhood = gigantism.

Adulthood = acromegaly.

Usually due to BENIGN GH secreting pituitary adenoma.

Question 7

What are the features of acromegaly?

Answer 7

 Insidious (gradual but harmful onset) in onset.
When untreated, excess GH is associated with increased morbidity and mortality.
Death: CVS (60%), respiratory complications (25%) and cancer (15%).

Growth – periosteal bone, cartilage, fibrous tissue, connective tissue, internal organs (i.e. hepatomegaly).

Question 8

What are the metabolic effects of acromegaly?

Answer 8

diabetes melitus development - excess GH -> inhibits insulin -> increased insulin resistance -> impaired glucose tolerance -> diabetes melitus

Question 9

What are the complications of acromegaly?

Answer 9

• Obstructive Sleep Apnoea - increased soft tissue growth in throat.
• Hypertension - effect of GH &/or IGF-1 on vascular tree, GH mediated Na reabsorption.
• Cardiomyopathy - hypertension, DM, toxic effects of GH on myocardium.
• Cancer – colonic polyps.

Prolactin is often high in acromegaly – reflects tumour secreting both GH and prolactin.

The hyperprolactinaemia will cause a secondary hypogonadism.

Question 10

How is acromegaly diagnossed?

Answer 10

GH is pulsatile and so random measurement is unhelpful however after an oral glucose load, the GH SHOULD drop in a healthy person as the insulin rises but in acromegaly, there is a PARADOXICAL RISE of GH.

There will be an elevated level of serum IGF-1 though so measure that.

Question 11

How is acromegaly treated?

Answer 11

1. Surgery – is FIRST line – trans-sphenoidal (under lip through sphenoid) entry and remove tumour.
2. Medical – Somatostatin analogues e.g. OCTREOTIDE , dopamine agonists e.g. CABERGOLINE, GH receptor agonist e.g PEGVISONANT

Somatostatin analogues – Endocrine cyanide.

• Injected or administered in a monthly depot injection.
• GI side effects common, e.g. nausea, diarrhoea, gallstones.
• Reduces GH secretion and tumour size.
• Also used as a pre-treatment before surgery (shrinks’ tumour).
• Can be used post-operatively if not cured or whilst waiting for radiotherapy to take effect.

3.Radiotherapy - could damage the rest of the pituootary -> hypoptituitarism -> lifelong steroid and thyroidal medication