Anterior pituitary hypersecretion

Question 1

What is the usual cause of hypersecretion of anterior pituitary hormones?

Answer 1

Pituitary adenoma

Question 2

What visual defect is associated with pituitary adenoma?

Answer 2

Bitemporal hemianopia

Question 3

What disease results from hypersecretion of Corticotrophin?

Answer 3

Cushing’s disease

Question 4

What disease results from hypersecretion of Thyrotrophin?

Answer 4

Thyrotoxicosis

Question 5

What disease results from hypersecretion of Gonadotrophin?

Answer 5

Precocious puberty in children

Question 6

What disease results from hypersecretion of Prolactin?

Answer 6

Hyperprolactinaemia – usually caused by prolactinomas Most commonly microadenomas (< 10 mm)

Symptoms: Loss of libido (Supresses GnRH)
Infertility
Galactorrhoea (rarely occurs in males as well) Oligomenorrhoea/amenorrhoea (women)
Impotence (in men)

Treated with Dopamine (D2 receptor) agonists – bromocriptine and cabergoline (more effective, less side effects) These can be temporary (few years) or life long is tumour persists

Question 7

Describe the pharmacokinetics and side-effects of bromocriptine.

Answer 7

Administered orally 1/day 
Heavily plasma protein bound 
Half-life = 7 hours (hepatic metabolism) 
Side effects: 
Nausea/vomiting/abdominal cramps 
Dyskinesias 
Psychomotor excitation 
Postural hypotension 
Vasospasm in fingers and toes

Question 8

State some other uses of bromocriptine.

Answer 8

Suppression of lactation
Cyclical benign breast tumours (and cyclic breast pain)
Also used in acromegaly but doesn’t have the same beneficial effect on tumour size
Parkinson’s disease

Question 9

Describe the pharmacokinetics and side-effects of cabergoline.

Answer 9

Taken orally 1-2/week
Half-life = > 45 hours
Side effect: same as bromocriptine but less pronounced

No nausea, vomiting or dyskinesias.

May cause psychosis E.G - Gambling addiction

Question 10

What disease results from hypersecretion of Somatotrophin?

Answer 10

Gigantism (in children)
Acromegaly (in adults)

Features: 
Prognathism 
Enlarged supraorbital ridges 
Enlarged soft tissue 
Hyperhydrosis 
Carpal tunnel syndrome (due to excessive cartilaginous growth) 
General coarseness of features 
Hypertension
Obstructive sleep apnoea (thick neck)

Increased insulin response to oral glucose leading to insulin resistance
This causes impaired glucose tolerance (in 50%) and diabetes mellitus (in 10%)

Question 11

What are the most serious complications of excess growth hormone?

Answer 11

Cardiovascular problems 60%
and respiratory problems 25%
This is mainly due to organ growth

Can also cause cancer 15%

Question 12

What type of test is used to diagnose a hyperpituitary disorder?

Answer 12

Suppression test

Question 13

What test is used to diagnose acromegaly and how are the results interpreted?

Answer 13

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

Question 14

State some of the treatments for acromegaly.

Answer 14

Transsphenoidal Hypophysectomy
Radiotherapy
Chemotherapy:
Octreotide (somatostatin analogue that is used short term to shrink neuroendocrine tumours before surgery or long term if only viable option)
Bromocriptine and Cabergoline (dopamine receptor agonists)

Question 15

Describe the administration, distribution, metabolism and side effects of octreotide.

Answer 15

Octreotide is administered SC or IM 3/day (It can be given as a monthly depot)
It is retained in extracellular fluid
Half-life = 2-4 hours
Causes GI tract disturbance (because somatostatin is produced by the small intestine as well)
Initial reduction in insulin secretion causing hyperglycaemia (octreotide inhibits the production of insulin by the beta cells)
Rarely gallstones

Question 16

What causes the side-effects of acromegaly?

Answer 16

Metabolic effects - increased plasma insulin response to oral glucose load, increased insulin resistance, impaired glucose tolerance and diabetes mellitus

Obstructive sleep apnoea - Bone and soft-tissue changes surrounding the upper airway lead to narrowing and subsequent collapse during sleep

Hypertension - Direct effects of GH &/or IGF-1 on vascular tree. GH mediated renal sodium reabsorption

Cardiomyopathy - Hypertension, DM, direct toxic effects of excess GH on myocardium

Increased risk of cancer - Colonic polyps, regular screening with colonoscopy

Prolactin may be co-secreted with GH in acromegaly -so patient may have high GH and high prolactin levels
(causing features of hyperprolactinaemia)