Growth Hormone and Acromegaly Flashcards
Which hormone can inhibit release of growth hormone from the anterior pituitary?
Somatostatin
What impact does growth hormone have on the liver?
- Increases liver gluconeogenesis
- Insulin growth factors (IGF-1) are released
How is glucose uptake affected by growth hormone
a) In the brain
b) In muscle cells
a) Increased
b) Decreased
Growth hormone has an impact on lipolysis
True or false?
True
It increases it allowing for more free energy sources in the body
IGF-1 is responsible for which two types of growth?
- Soft tissue
- Bone
What are the main anabolic effects of growth hormone on the body?
- Increases free glucose and fatty acids
- Increases protein synthesis
- Decreases fat storage
- Increases soft tissue growth (IGF-1)
- Increases bone growth (IGF-1)
Which physical changes can excess growth hormone have on the body?
- Prominent brow
- Large nose and jaw
- Pronounced cheek bones
- Skin changes
- Oral manifestations (difficulty eating/swallowing/dental pain/interdental separation)
- Large hands
How does excess growth hormone affect the hands and feet?
- Increase in size
- Spade-like hands
(it is a good idea to ask about shoes size changes)
How does excess growth hormone affect the skin?
- Thicker
- Excessive sweating
- Acne
- Greasier skin
How does excess growth hormone affect the face?
- Prominent supraorbital ridge (brow)
- Increased size and pronouncement of jaw (prognathism)
- Coarsening of facial features
- Enlarged tongue
- Tissue swelling in larynx
How does excess growth hormone affect the dentition?
- Interdental separation (mandible increases in size)
- Damage to teeth (due to overbite wear and tear)
How does excess growth hormone affect behaviour?
- Polyuria
- Polydipsia
- Lethargic (lack of sleep)
How does excess growth hormone affect sleep patterns?
- Causes obstructive sleep apnoea (tongue and larynx increase in size, snoring)
- Increased tissue growth in larynx can deepen /coarsen the voice
Which other conditions may occur as a complication of growth hormone excess?
- Diabetes (T2DM)
- Hypertension
- Carpal tunnel syndrome
Why can diabetes occur as a complication of growth hormone excess?
- Chronically raised plasma glucose
- Insulin sensitivity reduces
- Classic symptoms follow (polyuria, polydipsia, glucosuria, lethargy)
Why does hypertension occur as a complication of growth hormone excess?
- Increases lipolysis of fats occurs
- Increases fatty plaque production in arteries
- Hypertension follows
Why do people with growth hormone excess suffer from oily skin?
- Increase in lipolysis
- Plasma free fatty acids increase
- Oily skin develops as a result
Why does carpal tunnel syndrome occur as a complication of growth hormone excess?
- Increased growth of soft tissues in hands and forearms
- Compression of median nerve
Which hormones are produced by the hypothalamus that can have an impact on the production of growth hormone by the anterior pituitary?
- Growth hormone releasing hormone (GHRH)
- Somatostatin
What impact does IGF-1 have on
a) Anterior pituitary
b) Hypothalamus
a) Inhibits growth hormone production
b) Stimulates somatostatin production
What is the most likely cause for growth hormone hypersecretion?
Pituitary tumour
(may be ectopic carcinoid tumour, yet this is rarer)
Which two type of pituitary tumour can cause growth hormone hypersecretion?
- Microadenoma (<1cm)
- Macroadenoma (>1cm)
Why does giantism occur?
Excess IGF-1 acts on epiphyseal growth plates which have not yet fused causing growth
What may be the main complications of a pituitary macroadenoma versus a microadenoma?
- Headaches (due to compression)
- Compression of optic chiasm causing bitemporal hemianopia
- 1/3rd of cases are associated with hypersecretion of prolactin
- Compression can suppress other hormone production causing hypopituitarism
Why do growth hormone levels vary greatly throughout the day?
GHRH is released in a pulsatile manner
At which time in life does growth hormone usually peak?
Puberty
GH levels are _____ in pregnancy
GH levels are low in pregnancy
What is the definitive test for GH excess?
OGTT
Why does an OGTT work for determining growth hormone excess?
Normally high glucose levels inhibit growth hormone production
Failure to drop to undetectable levels shows there is autonomous secretion of GH
Describe the steps for an OGTT for GH excess
- Fast overnight
- At 9am take 300ml fluid with 75g of sugar
- Record plasma glucose levelsevery 30mins for 2 hours
What are the cut off values in an OGTT for excess growth hormone?
- No acromegaly GH is suppressed to <1mcg/L
- Acromegaly GH remains >1mcg/L
Levels of IGF-1 reflect ____ levels of GH
Levels of IGF-1 reflect 24hr levels of GH
Why are pituitary function tests essential in a patient with suspected acromegaly?
To determine if there is associated hypopituitarism
What are the treatment options for a pituitary tumour?
- Trans-sphenoidal surgery
- Radiotherapy
- Dopamine agonists
- Somatostatin receptor agonists
- Growth hormone antagonists
What are the downsides to using radiotherapy for a pituitary tumour?
- It may take a long time (10 years) to have an effect
- It may induce hypopituitarism
Which specific dopamine agonists can be used to treat acromegaly and what are their key benefits?
Bromocriptine, cabergoline
- Useful if the tumour also secretes prolactin
- Can reduce tumour size
- Prolactin release suppressed
Which specific somatostatin receptor agonists can be used to treat acromegaly and what are their key benefits?
Octreotide, Lanreotide
- Somatostatin analogues suppress GH release
- Can act quickly
Which specific growth hormone receptor antagonist can be used to treat acromegaly and what are the key benefits?
Pegvisomant
- Acts on GH receptors in cells in the body
- Can normalise IGF-1 levels
