Hypersecretion of Anterior Pituitary Hormones

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

State the disease resulting from hypersecretion of:

a. Corticotrophin
b. Thyrotrophin
c. Gonadotrophin
d. Prolactin
e. Somatotrophin

Answer 3

a. Cortictrophin 
Cushing’s disease 
b. Thyrotrophin 
Thyrotoxicosis
c. Gonadotrophins 
Precocious puberty in children
d. Prolactin 
Hyperprolactinaemia 
e. Somatotrophin 
Gigantism/Acromegaly

Question 4

What is the usual cause of hyperprolactinaemia?

Answer 4

Prolactinoma

Most commonly microadenomas (< 10 mm)

Question 5

State the symptoms of hyperprolactinaemia.

Answer 5

Loss of libido
Infertility
Galactorrhoea (rarely occurs in males as well) Oligomenorrhoea/amenorrhoea Impotence (in men)

Question 6

State two physiological causes of hyperprolactinaemia.

Answer 6

Pregnancy

Breast feeding

Question 7

What does excess growth hormone cause in children and in adults?

Answer 7

Children – gigantism

Adults – acromegaly

Question 8

What are the most serious complications of excess growth hormone?

Answer 8

Cardiovascular problems (majority) and respiratory problems  
This is mainly due to organ growth

Question 9

State some common clinical manifestations of acromegaly.

Answer 9

Prognathism 
Enlarged supraorbital ridges  
Enlarged soft tissue  
Hyperhydrosis  
Carpal tunnel syndrome (due to excessive cartilaginous growth) 
General coarseness of features 
Hypertension
macroglossia
barrel chest
Kyphosis (abnormal rounding of upper back)

Question 10

What are the metabolic effects of acromegaly?

Answer 10

Increased endogenous glucose production and decreased muscle glucose uptake
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 type of test is used to diagnose a hyperpituitary disorder?

Answer 11

Suppression test

Question 12

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

Answer 12

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 13

State some of the treatments for acromegaly.

Answer 13

Transsphenoidal Hypophysectomy 
Radiotherapy 
Chemotherapy: 
 Octreotide (somatostatin analogue)
 Bromocriptine and Cabergoline (dopamine receptor agonists)

Question 14

What are the clinical uses of octreotide?

Answer 14

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

Question 15

Describe the administration, distribution and metabolism of octreotide.

Answer 15

Octreotide is administered SC or IM 3/day
It is retained in extracellular fluid
Half-life = 2-4 hours

Question 16

State some of the side effects of octreotide.

Answer 16

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 17

What is used to treat hyperprolactinaemia?

Answer 17

Dopamine agonists – bromocriptine and cabergoline

Question 18

Describe the pharmacokinetics and side-effects of bromocriptine.

Answer 18

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

Question 19

State some other uses of bromocriptine.

Answer 19

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 20

Describe the pharmacokinetics and side-effects of cabergoline.

Answer 20

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

Question 21

Describe the visual field in a bitemporal hemianopia

Answer 21

Loss of peripheral vision of both eyes

Question 22

What is an ectopic tumour?

Answer 22

Tumours that are producing pituitary hormones but are not tumours of the pituitary.
E.g. Ectopic Cushing’s syndrome

Question 23

What effect does high prolactin have on GnRH?

Answer 23

Suppresses the GnRH pulsatility.

Question 24

What has dominant control over prolactin release?

Answer 24

Dopamine that acts on D2 receptors of the lactotroph.

Question 25

What are the general side effects of dopamine agonists?

Answer 25

Nausea and vomiting
Postural hypotension
Dsykinesias
Depression
Pathological gambling.

Question 26

What are some complications of acromegaly?

Answer 26

Obstructive sleep apnoea - Upper airway bone and soft tissue changes leads to narrowing and collapse during sleep
Hypertension - Direct effects of GH/IGF-1, GH mediated sodium reabsorption
Cadiomyopathy - Hypertension, toxic effects of GH on myocardium
Increased risk of cancer - GH is a cell stimulant, colonic polyps regular screening with colonoscopy.

Question 27

What other hormone is often high in acromegaly?

Answer 27

Prolactin - tumour may secrete both hormones

Hyperprolactinaemia will cause secondary hypogonadism