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

Endocrine Causes of Short Stature ✅ Flashcards

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
Q

What is the implication of the limitations of a GNRH stimulation test?

A

It is rarely used in childhood testing

26
Q

What is a high peak GH response defined as in stimulatory testing?

A

Over 8.5ng/dL

27
Q

What does a high peak GH response mean in stimulatory testing?

A

Excludes a diagnosis of GH deficiency

28
Q

What is defined as intermediate GH response in stimulatory testing?

A

5-8.3ng/dL

29
Q

What does an intermediate GH response to stimulatory testing suggest?

A

Suggests GH insufficiency if growth pattern is consistent with this diagnosis

30
Q

What is defined as low GH response in stimulatory testing?

A

<5ng/dL

31
Q

What does a low GH response to stimulatory testing suggest?

A

Severe forms of GH deficiency

32
Q

What is required to make a diagnosis of GH deficiency?

A

2 abnormal responses to GH testing, or 1 abnormal response with radiological evidence of intracranial abnormalities consistent with the diagnosis

33
Q

Why are 2 abnormal responses to GH testing required to make a diagnosis of deficiency in the UK?

A

Due to limited sensitivity and specificity of tests to diagnose GH deficiency

34
Q

What investigation should be done if a diagnosis of GH deficiency is made?

A

An MRI scan

35
Q

Why should an MRI be done if a diagnosis of GH deficiency is made?

A

To exclude an underlying tumour

36
Q

What tests should be considered when a diagnosis of GH deficiency is made?

A

Testing for wider pituitary dysfunction

37
Q

What should be obtained prior to treating GH deficiency?

A

Accurate growth data, preferably over a 1 year period

38
Q

Why is accurate growth data required prior to starting GH deficiency treatment?

A

To allow the benefits of GH treatment to be assessed

39
Q

How is synthetic GH produced?

A

Using recombinant DNA technology

40
Q

How is GH therapy administered?

A

Daily SC injection

41
Q

How should the growth response to GH therapy be evaluated?

A

Measurements every 4-6 months

42
Q

What is the level of response to GH therapy related to?

A
  • 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
Q

What can be done by taking into account factors that affect the effectiveness of GH therapy?

A

Predict the response to GH and ‘personalise’ the dose of GH

44
Q

What is the advantage of personalising the dose of GH?

A

Ensure maximal and cost-effective response

45
Q

When does the maximal growth response to GH therapy occur?

A

In the first year

46
Q

What happens to the effectiveness of GH after the first year?

A

Tachyphylaxis

47
Q

What does tachyphylaxis mean?

A

The appearance of progressive decrease in response to a given dose after repetitive administration of a pharmacologically or physiologically active substance

48
Q

What causes tachyphylaxis of GH therapy after the first year?

A

Down-regulation of the GH receptor

49
Q

What is indicative of a successful response to GH therapy?

A

An increase in height-velocity of at least 2cm/year

50
Q

What should be done if there is a less than 2cm/year increase in growth velocity with GH therapy?

A
  • Consider adherence
  • Consider if wrong diagnosis
  • Consider discontinuation of therapy
51
Q

What should be done with GH therapy once growth is complete after puberty?

A

GH testing should be repeated

52
Q

Why should GH testing be repeated once growth is complete at the end of puberty?

A

Mild forms of GH deficiency do not require ongoing therapy into adult life

53
Q

Why do milder forms of GH deficiency not require ongoing therapy into adult life?

A

During adult life lower levels of GH are required

54
Q

What is GH required for in adult life?

A
  • Maintenance of normal body composition
  • Bone health
  • Avoidance of cardiovascular risk factors
55
Q

What monitoring is required during GH therapy?

A

Ongoing monitoring for wider defects in pituitary function

56
Q

When is GH therapy ineffective?

A

In the very rare circumstance of GH resistance

57
Q

What is used to treat GH resistance?

A

Recombinant IGF-1

58
Q

Does congenital or acquired hypothyroidism cause growth failure?

A

Both

59
Q

Why does hypothyroidism cause growth failure?

A
  • Suppresses GH secretion

- Growth and anabolic effects of GH and IGF-1 are downregualted

60
Q

Why are the growth and anabolic effects of GH and IGF-1 downregulated in hypothyroidism?

A

Due to the absence of thyroid hormone action through its receptor sites

61
Q

How can the growth failure caused by hypothyroidism be reversed?

A

Thyroxine treatmnt

62
Q

How does Cushing’s syndrome cause growth failure?

A

Excess cortisol levels directly suppress GH secretion and action, and delay onset of puberty

TAS Growth And Puberty ✅ (12 decks)

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