Hypersecretion of anterior pituitary hormones

Question 1

What is hyperpituitarism?

Answer 1

Excess production of adenohypophysial hormones.

Question 2

What is hyperpituitarism usually caused by?

Answer 2

Isolated pituitary tumours

Can also be ectopic (i.e. from non-endocrine tissue), e.g. vasopressin-producing lung tumours

Question 3

What defects is hyperpituitarism commonly associated with?

Answer 3

Visual field defects

Cranial nerve defects- effects on nearby structures to the pituitary

Question 4

How may hyperpituitarism result in loss of temporal vision?

Answer 4

At the optic chiasm, fibres from the nasal retinae cross. Light from the temporal aspect of the visual fields strikes the nasal aspect of the retina. Compression of these fibres e.g. by a pituitary tumour protruding out of the sella turcica may result in bitemporal (heteronymous) hemianopia.

Question 5

What does excess ACTH (corticotrophin) result in?

Answer 5

Cushing’s disease

Question 6

What does excess TSH (thyrotrophin) result in?

Answer 6

Thyrotoxicosis

Question 7

What does excess FSH/LH (gonadotrophins) result in?

Answer 7

Precocious puberty in children

Question 8

What does excess prolactin result in?

Answer 8

Hyperprolactinaemia

Question 9

What does excess GH result in?

Answer 9

Gigantism (children); acromegaly (adults)

Question 10

What is hyperprolactinaemia?

Answer 10

Excess circulating prolactin due to physiological (pregnancy or breastfeeding) or pathological (prolactinoma- microadenoma) causes.

Question 11

What can hyperprolactinaemia due to prolactinoma result in in women?

Answer 11

Galactorrhoea
Secondary amenorrhoea (low LH and FSH)
Loss of libido
Infertility

Question 12

What can hyperprolactinaemia due to prolactinoma result in in men?

Answer 12

Loss of libido
Impotence
Infertility
Galactorrhoea uncommon (appropriate steroid background usually inadequate)

Question 13

What is the first-line treatment for hyperprolactinaemia?

Answer 13

Dopamine receptor (D2) agonists, e.g. bromocriptine, cabergoline- decrease prolactin secretion and reduce tumour size. Oral administration.

Question 14

Name some side effects of dopamine receptor (D2) agonists used to treat hyperprolactinaemia.

Answer 14

Nausea and vomiting
Postural hypotension
Dyskinesias
Depression
Pathological gambling

Question 15

What is acromegaly?

Answer 15

Excess somatotrophin (GH) in adults. The growth plates of the long bones have fused so there is no longer a possibility of an increase in height- still get other effects.
It has insidious onset- signs and symptoms progress gradually over many years.

Question 16

What happens if acromegaly/gigantism is left untreated?

Answer 16

Associated with increased morbidity and mortality due to cardiovascular (majority) and respiratory complications. It is not just increased growth but also increased organ size. This means there is increased demand for oxygen and the blood supply must keep up with this extra demand- big strain on CVS.

Question 17

What symptoms are associated with acromegaly?

Answer 17

Increased growth of periosteal bone, cartilage, fibrous tissue, connective tissue, internal organs (cardiomegaly, hepatomegaly, splenomegaly, etc.)
Prognathism
Enlarged supraorbital ridges and soft tissues
Excessive sweating (hyperhidrosis)
Headaches
Macroglossia
Carpal tunnel syndrome
Barrel chest
Kyphosis

Question 18

What are the metabolic effects of acromegaly?

Answer 18

Excess GH causes increased endogenous glucose production and decreased muscle glucose uptake. This leads to increased insulin production and thus increased insulin resistance. There is then impaired glucose tolerance (50% patients) and subsequent diabetes mellitus (10% patients).

Question 19

Name some complications of acromegaly.

Answer 19

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 and/or IGF-1 on vascular tree; GH-mediated renal sodium reabsorption.
Cardiomyopathy- hypertension, DM, direct toxic effects of excess GH on myocardium.
Cancer- colonic polyps, regular screening with colonoscopy.

Question 20

How are pituitary hypersecretory states diagnosed?

Answer 20

Suppression tests

Question 21

How is acromegaly diagnosed?

Answer 21

Glucose-induced suppression of growth hormone secretion (oral glucose tolerance test).
Glucose should inhibit GH release so GH levels will decrease, with an over-swing at the end.
In a patient with acromegaly, there is a paradoxical rise in GH following administration of glucose.
Elevated serum IGF-1.

Question 22

How is acromegaly treated?

Answer 22

Surgery (trans-sphenoidal) is first-line.
Medical treatments include somatostatin analogues, e.g. octreotide, and dopamine agonists (GH secreting pituitary tumours frequently express D2 receptors), e.g. cabergoline.
Radiotherapy may also be used.

Question 23

What are somatostatin analogues used for?

Answer 23

‘Endocrine cyanide’, subcutaneous injection (short acting) or monthly depot.
Reduce GH secretion and tumour size.
Pre-treatment before surgery may make resection easier.
Use post-operatively if not cured or whilst waiting for radiotherapy to take effect (slow).
GI side effects are common, e.g. nausea, diarrhoea, gallstones can occur.