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TAS Growth And Puberty ✅ > Endocrine Causes of Short Stature ✅ > Flashcards

Endocrine Causes of Short Stature ✅ Flashcards

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1
Q

What are the endocrine causes of growth failure?

A
  • GH deficiency
  • Hypothyroidism
  • Cushing’s syndrome
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2
Q

What is growth hormone deficiency characterised by?

A
  • Growth failure
  • Delayed skeletal maturation and puberty
  • Increased body fat
  • Micropenis
  • Hypoglycaemia in infancy
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3
Q

When does GH deficiency cause hypoglycaemia in infancy?

A

When severe

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4
Q

What features may be present when GH deficiency is caused by hypopituitarism?

A
  • Signs of TSH, ACTH, and gonadotrophin deficiencies
  • Midline craniofacial skeletal abnormalities
  • Optic atrophy and visual impairment
  • Signs of raised ICP
  • Bitemporal hemianopia
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5
Q

What does optic atrophy and visual impairment alongside GH deficiency suggest?

A

Septo-opticd dysplasia

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6
Q

What does bitemporal hemianopia alongside GH deficiency suggest?

A

Pituitary tumour compressing optic chiasm

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7
Q

What does a family history of other similarly affected individuals in GH deficiency suggest?

A

A mutation in GHRH or GH-1 gene, or genes that encode transcription factors involved in pituitary development

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8
Q

When is investigation for possible GH deficiency indicated?

A

Once baseline investigations for non-GH-related causes of short stature have been performed and found to be normal

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9
Q

What are the options for measuring GH levels?

A
  • Random blood sample measuring
  • Monitoring blood samples every 20 minutes to produce a 24 hour GH secretory profile
  • Stimulatory tests
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10
Q

Why is using random blood samples to measure GH levels generally unhelpful?

A

GH is secreted in a pulsatile fashion, so levels are low throughout most of a 24 hour period

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11
Q

What are the options for measuring GH levels?

A
  • Random blood sample measuring
  • Monitoring blood samples every 20 minutes to produce a 24 hour GH secretory profile
  • Stimulatory tests
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12
Q

What are the options for measuring GH levels?

A
  • Random blood sample measuring
  • Monitoring blood samples every 20 minutes to produce a 24 hour GH secretory profile
  • Stimulatory tests
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13
Q

What is the limitation of measuring blood samples every 20 minutes to produce a 24 hour GH secretory profile?

A

It is challenging to organise and interpret

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14
Q

What is the most clinically useful way to diagnose GH deficiency?

A

Stimulatory tests of GH secretion

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15
Q

What is the gold standard GH stimulation test?

A

Insulin-induced hypoglycaemia

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16
Q

What effect does insulin-induced hypoglycaemia have on GH?

A

It promotes a counter-regularity GH secretory response

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17
Q

Other than GH levels, what does insulin-induced hypoglycaemia allow the measurement of?

A

ADTH-induced cortisol response

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18
Q

What is the limitation of insulin-induced hypoglycaemia to test for GH?

A

It is potentially dangerous, and should only be performed in children over 5 years old in units experienced in its use

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19
Q

What are the alternative options for stimulatory tests of GH secretion?

A
  • Glucagon
  • Clonidine
  • Arginine
  • GNRH
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20
Q

What does glucagon stimulate?

A

Secretion of GH and cortisol

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21
Q

What does clonidine stimulate?

A

Secretion of GH alone

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22
Q

What does arginine stimulate?

A

Secretion of GH alone

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23
Q

What does GNRH stimulate?

A

The pituitary directly

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24
Q

What is the limitation of a GNRH stimulation test?

A

It is poor at distinguishing hypothalamic forms of GH deficiency from a normal short child

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25
What is the implication of the limitations of a GNRH stimulation test?
It is rarely used in childhood testing
26
What is a high peak GH response defined as in stimulatory testing?
Over 8.5ng/dL
27
What does a high peak GH response mean in stimulatory testing?
Excludes a diagnosis of GH deficiency
28
What is defined as intermediate GH response in stimulatory testing?
5-8.3ng/dL
29
What does an intermediate GH response to stimulatory testing suggest?
Suggests GH insufficiency if growth pattern is consistent with this diagnosis
30
What is defined as low GH response in stimulatory testing?
<5ng/dL
31
What does a low GH response to stimulatory testing suggest?
Severe forms of GH deficiency
32
What is required to make a diagnosis of GH deficiency?
2 abnormal responses to GH testing, or 1 abnormal response with radiological evidence of intracranial abnormalities consistent with the diagnosis
33
Why are 2 abnormal responses to GH testing required to make a diagnosis of deficiency in the UK?
Due to limited sensitivity and specificity of tests to diagnose GH deficiency
34
What investigation should be done if a diagnosis of GH deficiency is made?
An MRI scan
35
Why should an MRI be done if a diagnosis of GH deficiency is made?
To exclude an underlying tumour
36
What tests should be considered when a diagnosis of GH deficiency is made?
Testing for wider pituitary dysfunction
37
What should be obtained prior to treating GH deficiency?
Accurate growth data, preferably over a 1 year period
38
Why is accurate growth data required prior to starting GH deficiency treatment?
To allow the benefits of GH treatment to be assessed
39
How is synthetic GH produced?
Using recombinant DNA technology
40
How is GH therapy administered?
Daily SC injection
41
How should the growth response to GH therapy be evaluated?
Measurements every 4-6 months
42
What is the level of response to GH therapy related to?
- Severity of deficiency - Pre-treatment height velocity - Age - Difference in child's height from parent's height - Birth weight - Current weight - Dose of GH
43
What can be done by taking into account factors that affect the effectiveness of GH therapy?
Predict the response to GH and 'personalise' the dose of GH
44
What is the advantage of personalising the dose of GH?
Ensure maximal and cost-effective response
45
When does the maximal growth response to GH therapy occur?
In the first year
46
What happens to the effectiveness of GH after the first year?
Tachyphylaxis
47
What does tachyphylaxis mean?
The appearance of progressive decrease in response to a given dose after repetitive administration of a pharmacologically or physiologically active substance
48
What causes tachyphylaxis of GH therapy after the first year?
Down-regulation of the GH receptor
49
What is indicative of a successful response to GH therapy?
An increase in height-velocity of at least 2cm/year
50
What should be done if there is a less than 2cm/year increase in growth velocity with GH therapy?
- Consider adherence - Consider if wrong diagnosis - Consider discontinuation of therapy
51
What should be done with GH therapy once growth is complete after puberty?
GH testing should be repeated
52
Why should GH testing be repeated once growth is complete at the end of puberty?
Mild forms of GH deficiency do not require ongoing therapy into adult life
53
Why do milder forms of GH deficiency not require ongoing therapy into adult life?
During adult life lower levels of GH are required
54
What is GH required for in adult life?
- Maintenance of normal body composition - Bone health - Avoidance of cardiovascular risk factors
55
What monitoring is required during GH therapy?
Ongoing monitoring for wider defects in pituitary function
56
When is GH therapy ineffective?
In the very rare circumstance of GH resistance
57
What is used to treat GH resistance?
Recombinant IGF-1
58
Does congenital or acquired hypothyroidism cause growth failure?
Both
59
Why does hypothyroidism cause growth failure?
- Suppresses GH secretion | - Growth and anabolic effects of GH and IGF-1 are downregualted
60
Why are the growth and anabolic effects of GH and IGF-1 downregulated in hypothyroidism?
Due to the absence of thyroid hormone action through its receptor sites
61
How can the growth failure caused by hypothyroidism be reversed?
Thyroxine treatmnt
62
How does Cushing's syndrome cause growth failure?
Excess cortisol levels directly suppress GH secretion and action, and delay onset of puberty

TAS Growth And Puberty ✅ (12 decks)

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