Hypersecretion of anterior pituitary hormones

Question 1

What are the main causes of hyper-secretion of adenohypophysial hormones?

Answer 1

Pituitary adenoma

Tumours from non-endocrine tissue (ectopic in origin)

Question 2

What visual field defect is associated with pituitary adenoma, and why?

Answer 2

Bitemporal hemianopia

Due to compression of the optic chiasm by growth of suprasellar tumour

Question 3

State the disease resulting from hypersecretion of:

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

Answer 3

Cushing's disease
Thyrotoxicosis
Precocious puberty in children
Hyperprolactinaemia
Gigantism, Acromegaly

Question 4

State when hyperprolactinaemia may be physiological and when it may be pathological

Answer 4

Physiological = pregnancy, breastfeeding

Pathological = prolactinoma (often microadenomas < 10mm diameter); most common functioning pituitary tumour
**High prolactin suppresses GnRH pulsatility

Question 5

State the symptoms of hyperprolactinaemia in women

Answer 5

• Galactorrhoea (milk production)
• Secondary amenorrhoea (or oligomenorrhoea)
• Loss of libido
• Infertility

Question 6

State the symptoms of hyperprolactinaemia in men

Answer 6

• Galactorrhoea uncommon (since appropriate steroid background usually inadequate)
• Loss of libido
• Erectile dysfunction
• Infertility

Question 7

How does dopamine affect prolactin secretion

Answer 7

Dopamine released from hypothalamic dopaminergic neurones bind to D2 receptors on lactotrophs, inhibiting prolactin release

Question 8

How is hyperprolactinaemia treated?

Answer 8

Oral administration of dopamine receptor (D2) agonists - decrease prolactin secretion and reduce tumour size

Question 9

Give two examples of dopamine receptor (D2) agonists

Answer 9

BROMOCRIPTINE

CABERGOLINE

Question 10

List some side effects of dopamine receptor agonists

Answer 10

Nausea and vomiting
Postural hypotension
Dyskinesias
Depression
Impulse control disorder e.g. pathological gambling, hyper sexuality

Question 11

Excess growth hormone in childhood results in ………….

Answer 11

GIGANTISM

Question 12

Excess growth hormone in adulthood results in ………….

Answer 12

ACROMEGALY

Question 13

What are the most serious complications of excess growth hormone?

Answer 13

Cardiovascular disease 60%
Respiratory complications 25%
Cancer 15%

Question 14

Describe the onset of acromegaly

Answer 14

Insidious

Question 15

What grows in acromegaly?

Answer 15

• Periosteal bone
• Cartilage
• Fibrous tissue
• Connective tissue
• Internal organs (cardiomegaly, splenomegaly, hepatomegaly, etc.)

Question 16

State the clinical features of acromegaly excessive sweating

Answer 16

• Excessive sweating (hyperhidrosis)
• Headache
• Enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features
• Macroglossia
• Prognathism
• Carpal tunnel syndrome (median nerve compression)
• Barrel chest, kyphosis

Question 17

How might a patient help with the diagnosis of acromegaly

Answer 17

Patients can bring old photos

Question 18

What is the metabolic effect of acromegaly?

Answer 18

Excess GH => increased endogenous glucose production,
decreased muscle glucose uptake => increased insulin production => increased insulin resistance => impaired glucose tolerance => DIABETES MELLITUS

Question 19

What other complications are there associated with acromegaly?

Answer 19

• Obstructive sleep apnoea
• Hypertension (GH mediated renal sodium reabsorption)
• Cardiomyopathy (due to hypertension, DM or direct toxic effects of excess GH)
• Increased risk of cancer

Question 20

What other anterior pituitary hormone may be co-secreted in high amounts with GH, especially in younger patients?

Answer 20

Prolactin

Question 21

How is acromegaly diagnosed biochemically?

Answer 21

Elevated serum IGF-1 following oral glucose load (oral glucose tolerance test) due to failed suppression/paradoxical rise in GH

Question 22

Summarise the treatment of acromegaly

Answer 22

1st LINE:
- Surgical removal of tumour (trans-sphenoidal)

MEDICAL:

• Somatostatin analogues e.g. OCTREOTIDE; sub cut/monthly depot injection
• Dopamine receptor agonists (because GH secreting pituitary tumours frequently express D2 receptors)

RADIOTHERAPY (especially for large tumours)

Question 23

State the side effects of somatostatin analogues, and when specifically might it be used

Answer 23

‘Endocrine cyanide’
- GI side effects common (e.g. nausea, diarrhoea, gallstones)

Used before surgery for ease of resection, and post-operatively if not cured or during radiotherapy