HYPERSECRETION OF ANTERIOR PITUITARY HORMONES

Question 1

Outline some features of hyperpituitarism.

Answer 1

usually due to pituitary tumours (also ectopic)

Often associated with visual field defects.

Endocrine related signs and symptoms.

Question 2

What can happen as a result of a pituitary tumour compressing the optic chiasm?

Answer 2

bitemporal hemianopia.

Question 3

What is bitemporal hemianopia?

Answer 3

Loss of preipheral vision

Question 4

What diseases are caused by excess ACTH, TSH, LH/FSH, Prolactin and GH?

Answer 4

ACTH - cushing’s

TSH - thyrotoxicosis.

LH/FSH - precocious puberty in children

Prolactin - hyperprolactinaemia.

GH - gigantism (child), acromegaly (adult)

Question 5

Give 3 causes of hyperprolactinaemia.

Answer 5

Physiological - pregnancy, breastfeeding.

Pathological - prolactinoma (often small) - most common pituitary tumour.

Question 6

What additional problem is presented by high prolactin.

Answer 6

suppression of GnRH pulsatility.

Question 7

GIve symptoms and signs of hyperprolactinaemia due to pituitary adenoma in men and women.

Answer 7

Women - galactorrhoea (milk production), secondary amenorrhoea, loss of libido, infertility.

Men - galactorrhoea, loss of libido, erectile dysfunction, infertility.

Question 8

What secretes prolactin?

Answer 8

anterior pituitary lactotroph.

Question 9

How can release of prolactin be inhibited?

Answer 9

Binding of dopamine from hypothalamic dopaminergic neurones to D2 receptors (hence D2 agonists can be used to inhibit prolactin).

Question 10

What is the first line of hyperprolactinaemia treatment? How is it administered? Examples.

Answer 10

Dopamine receptor (D2) agonists.

• reducde prolactin secretion.
• reduce tumour size.

Oral administration.

e.g. bromocriptine, cabergoline.

Question 11

Give some side effects of dopamine receptor agonists.

Answer 11

Nausea and vomiting

Postural hypotension

Dyskinesias

Depression

Question 12

Why is acromegaly difficult to diagnose.

Answer 12

In men, symptoms progress slowly (in women periods go awry).

Question 13

What are the results of excess GH?

Answer 13

Increased morbidity and mortality.

Question 14

What are the most common causes of death in agromegaly patients?

Answer 14

CVD - 60%

respiratory complications - 25%

Cancer - 15%

Question 15

What grows in acromegaly?

Answer 15

• periosteal bone
• cartilage
• fibrous tissue
• connective tissue
• internal organs (cardiomegaly, splenomegaly, hepatomegaly, etc.)

Question 16

List the clinical features of acromegaly (7).

Answer 16

• Excessive sweating.
• Headache
• enlarged tongue
• barrel chest
• carpal tunnel syndrome.
• lower jaw protrusion (mandible growth).
• enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features

Question 17

Outline the metabolic effects of acromegaly relating to insulin.

Answer 17

excess growth hormone –> increased endogenous glucose production, decreased muscle glucose uptake –> increased insulin production = increased insulin resistance –> impaired glucose tolerance –> diabetes mellitus.

Question 18

List and explain some complications of acromegaly.

Answer 18

Obstructive sleep apnoea

Hypertension

• directly as a result of GH or due to GH mediated renal Na+ reabsorption.

Cardiomyopathy

-hypertension, direct toxic effects of excess GH on myocardium.

Increased cancer risk

• colonic polyps, regular screening with colonoscopy.

Question 19

Why is hypogonadism associated with acromegaly?

Answer 19

Prolactin often high in acromegaly - e.g. due to tumour secreting GH and prolactin..

Question 20

Give 2 ways acromegaly can br diagnosed.

Answer 20

Elevated serum IGF-1.

Failed suppression of GH following oral glucose load.

Question 21

Outline change in GH during oral glucose tolerance test in someone with acromegaly relative to a normal person.

Answer 21

Paradoxical increase (decrease in normal)

Question 22

List 4 potential treatments of acromegaly.

Answer 22

Surgery

Somatostatin analogues e.g. octreotide

Dopamine agonists e.g. cabergoline

Radiotherapy.

Question 23

Name some common side effects from somatostatin analogues.

Answer 23

Nausea, diarrhoea, gallstones.

Question 24

What are the uses of somatostatin analogues?

Answer 24

Reduce GH secretion and tumour size

pre-treatment before surgery makes reduction easier.

Used post-operatively if not cured while waiting for radiotherapy to take effect.