Hypersecretion of Anterior Pituitary Hormones

Question 1

What is hyperpituitarism

Answer 1

Symptoms associated with excess production of adenohypophyisal hormones

Question 2

Describe the causes and associations of hyperpituitarism

Answer 2

Usually due to isolated pituitary tumour
May also be ectopic in origin
Can be often associated with visual field and other (e.g. cranial nerve) defects and endocrine-related signs and symptoms

Question 3

Why do pituitary tumours often cause visual field defects

Answer 3

At the optic chiasm, fibres from the nasal retinae cross
Light from the outer aspects of the visual fields strikes the nasal aspect
Compression of the crossing fibres at the optic chiasm causes a loss of vision from the outer temporal visual fields
(bitemporal hemianopia)

Question 4

What can hyperpituitarism result in (adenohypophysis-hypophysis)

Answer 4

ACTH -> Cushings
TSH -> thyrotoxicosis
Gonadotrophins -> precocious puberty in children
Prolactin -> Hyperprolactinaemia
GH -> Gigantism, acromegaly

Question 5

What are the physiological and pathological causes of hyperprolactinaemia

Answer 5

Physiological - pregnancy, breastfeeding

Pathological - Prolactinoma (often micro adenomas <10mm)

Question 6

What is the most common functioning pituitary tumour

Answer 6

Prolactinoma

Question 7

How does prolactin affect GnRH

Answer 7

high prolactin suppresses GnRH pulsality

Question 8

What are the symptoms of hyperprolactinaemia due to pituitary adenoma in women

Answer 8

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

Question 9

What are the symptoms of hyperprolactinaemia due to pituitary adenoma in men

Answer 9

Galactorrhoea uncommon
Loss of libido
Erectile dysfunction
Infertility

Question 10

How is prolactin secretion regulated

Answer 10

Dopamine from the hypothalamus binds to the D2 receptors on the lactotrophs and prevent prolactin secretion

Question 11

How is a hyperprolactinaemia treated

Answer 11

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

Question 12

What are the side effects of dopamine receptor agonists

Answer 12

Nausea and vomiting
Postural hypotension 
Dyskinesias 
Depression
Impulse control disorder (pathological gambling, hyper sexuality)

Question 13

What are the effects of excess GH in childhood and adulthood

Answer 13

child - gigantism
adult - acromegaly
Usually due to benign growth hormone secreting pituitary adenoma

Question 14

Describe acromegaly

Answer 14

Signs and symptoms progress gradually 
Untreated it is associated with increased morbidity and mortality
Cardiovascular disease - 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

What are the clinical features of acromegaly

Answer 16

Excessive sweating (hyperhidrosis)
Headache
Enlargement of supraorbital ridges, nose, hands and feet , thickening of lips
Enlarged tongue (macroglossia)
Mandible grows -> jaw protusion (prognathism)
Carpal tunnel syndrome (median nerve compression)
Barrel chest, kyphosis

Question 17

What are the metabolic effects of acromegaly

Answer 17

1. Increased endogenous glucose production, decreased muscle glucose uptake
2. Increased insulin production -> insulin resistance
3. Impaired glucose tolerance
4. Diabetes mellitus

Question 18

What are the complication of acromegaly

Answer 18

Obstructive sleep apnoea
Hypertension
Cardiomyopathy
Increased risk of cancer

Question 19

Describe the co-secretion of prolactin and GH in acromegaly

Answer 19

Prolactin is often high in acromegaly

Hyperprolactinaemia will cause secondary hypogonadism

Question 20

How is acromegaly diagnosed

Answer 20

Elevated serum IGF-1
Failed suppression of GH following oral glucose load (oral glucose tolerance)
(GH is pulsatile - unhelpful)

Question 21

Describe what happens when oral glucose is given for diagnosis acromegaly

Answer 21

Increase in GH in response to glucose (no explanation, just used for diagnosis), which then returns to normal after 2 hours
Those who are normal will see a decrease in GH and then increases after 2 hours, then decreasing after 2.5 hours

Question 22

What is the treatment of acromegaly

Answer 22

Surgery (trans-sphenoidal)
Somatostatin analogues e.g. octreotide
Dopamine agonists e.g. cabergoline
Radiotherapy

Question 23

Describe somatostatin analogues

Answer 23

Injection (short acting) or monthly depot
Reduces GH secretion and tumour size
Pre-treatment before surgery may make it easier
Use post-operatively if not cured or whilst waiting for radiotherapy to take effect

Question 24

What are the side effects of somatostatin analogues

Answer 24

Nausea
Diarrhoea
Gallstones