Growth, Endocrine and Metabolism Flashcards
What are the most common chronic diseases in childhood?
1) Asthma
2) Cerebral Palsy
3) Type 1 DM
List some types of diabetes found in children
1) T1DM (95%)
2) T2DM (1-2%)
3) MODY
4) Steroid induced DM
5) CF related DM
What is MODY?
Maturity-onset diabetes of the young
Monogenic = single gene defects of pancreatic SUR1 and Kir6.2 sub units of K+ channels in beta cells leading to impaired insulin secretion
What is the inheritance pattern of MODY?
Autosomal dominant
Which 2 groups of children tend to suffer steroid induced DM?
Post-transplant
Oncology
What is aetiology of T1DM?
Some evidence of genetic predisposition but often no FHx (FHx much more common in T2DM)
Autoimmune (T-cell mediated) damage of beta cells in islets of Langerhans
Children often develop T1DM after unknown trigger such as viral infection or diet
What gene is implicated in T1DM?
HLA DR3 and DR4
human leukocyte antigen
What is the pathophysiology of type 1 diabetes?
T-cell mediated autoimmune destruction of beta cells in pancreatic islets of Langerhans
Results in inability to secrete insulin therefore inability of cells to uptake blood glucose leading to hyperglycaemia
This results in a catabolic state with increased glycogenolysis, gluconeogenesis and lipolysis
Hyperglycaemia exceeds renal threshold leading to dehydration and electrolyte loss by osmotic diuresis
What is the % chance if one identical twin has T1DM that the other twin will also?
30%
In T1DM there is beta-cell destruction. At what % mass destruction does presentation usually occur?
50% (early) - 90% (late)
What is the peak age of onset of T1DM?
Age 5-7yrs (but increasing in toddlers) and just before the onset of puberty
What are the four T’s aimed to improve early recognition of T1DM?
Thirst
Toilet
Tired
Thin
How does T1DM present?
Several weeks of polyuria Lethargy Polydipsia Weight loss \+/- infection / poor growth / ketosis
What are the effects of insulin on:
1) Skeletal muscle
2) Liver
3) Adipose tissue?
1) Skeletal muscle
- Increased glycogenesis
- Increased protein synthesis
2) Liver
- Increased glycogenesis
- Decreased gluconeogenesis
3) Adipose tissue
- Increased adipogenesis
- Decreased lipolysis
How is T1DM confirmed?
WHO diagnostic criteria:
Signs of hyperglycaemia AND:
Random blood glucose at or above 11mmol/L
or fasting blood glucose at or above 7mmol/L
OR
No symptoms but raised blood glucose on 2 occasions
Oral glucose tolerance tests (OGTT) rarely required in children
What is the most common regime of managing T1DM?
Mixture of rapid acting and long acting insulin injected subcutaneously depending on daily insulin requirement
- 5-1 units/kg/24hr = prepubertal
- 5/units/kg/24hr = pubertal
How is insulin injected and why are different sites used?
Subcutaneously into arms, thighs and abdomen
Different sites used to avoid lipohypertrophy
Which hormones increase / decrease glucose levels?
Decrease blood glucose:
- Insulin
- Somatostatin (growth hormone inhibiting hormone)
Increase blood glucose = counter-regulatory hormones:
- Glucagon
- Cortisol
- Oestrogen
- Testosterone
- GH
- Adrenaline / noradrenaline
Why do continuous SC insulin pumps have diurnal variations in their basal dose (as well as bolus during mealtimes)?
Due to the diurnal variation of counter-regulatory hormones GH and cortisol
List three other methods of managing T1DM
1) Short-acting basal bolus with meals and long-acting (lasts 24 hours) at night
2) Multidose regime using insulin pen
3) Continuous subcutaneous pump with basal bolus (pump)
Below what mmol/L is considered hypoglycaemic in a diabetic pt?
Why is this not the same in an individual who does not suffer from DM?
<4mmol/L (4 = floor)
Those without DM may have blood glucose lower than this, however this is not as concerning as the body will identify this and their pancreatic insulin secretion will be adjusted accordingly
Those with DM are receiving exogenous insulin and thus will hypo further = more concerning
How can exogenous and endogenous insulin be differentiated ie if someone has had a hypo, what could you measure to identify if this was from injected insulin or from what the body has produced?
Insulin is produced in the body as a pre-insulin attached to C-peptide which is cleaved
High levels of C-peptide indicate high endogenous insulin
What OGTT is diagnostic of T1DM?
At or above 11mmol/l
What HbA1c is diagnostic of T1DM?
At or above 6.5% or 48mmol
What is given in hypoglycaemia?
If conscious:
- Lucozade, fruit juice, jelly babies, glucose tablets eg lift
General rules:
5g of glucose for 10kg child
10g of glucose for 30kg child
15g of glucose for 50kg child
If unconscious:
- Glucagon (good as works fast) - comes as powder that needs to be made up with water for injection
Give an example of a rapid and long acting insulin
Rapid acting
- Humalog
- Actrapid
- Aspart
- Novorapid
Long acting
- Lantus
- Levemir
What is the ‘honeymoon period’?
A period post diagnosis where insulin requirement is low
This is because there is still some pancreatic beta cells functioning
Period can vary from months to sometimes years - aim is to prolong this period for as long as possible
Greater pancreatic function at presentation = longer honeymoon period
List some pros of continuous insulin pumps
Great for compliance Fewer injections Increased lifestyle flexibility Accurate delivery Fewer hypos
List some cons of continuous insulin pumps
Cost
Risk of superficial infections
Pump failure can lead to DKA
Inconvenience of wearing an external pump / cosmetic
What should blood glucose be first thing in the morning?
4-7mmol/L
What often tends to happen with insulin requirements after initial use?
They increase after ‘honeymoon’ period
What is DKA?
Leading cause of mortality in childhood DM
Either absolute or relative insulin deficiency
What causes an absolute insulin deficiency in a child with DKA?
Previously undiagnosed T1DM or pt noncompliant with their insulin
What causes an relative insulin deficiency in a child with DKA?
Stress causes a rise in counter-regulatory hormones with relative insulin deficiency
eg catecholamines, glucagon, cortisol, growth hormone (eg in sepsis)
What is the pathophysiology of DKA?
Insulin deficiency means that when there is an increase in plasma glucose the glucose cannot enter the cells
The body think its in starvation so lipolysis occurs which produces fatty acids which are converted in the liver into ketones
High plasma glucose causes an osmotic diuresis (increase urination)
Dehydration + LOTS of LOSS of electrolytes (esp sodium and potassium):
- Untreated DKA leads to metabolic acidosis which causes potassium to go out of cells and hydrogen in
- Also the insulin deficiency leads to potassium to go out of cells
- When treated with insulin, potassium moves from EXTRAcellular space to INTRAceullular space which can cause profound hypokalaemia
SO basically in DKA blood potassium is deceptively high, it has all moved extracellularly so true value is lower
What vicious cycle occurs in DKA? How can it be broken?
Vomiting often occurs, compounding the stress and dehydration
= Can only be broken by providing insulin and fluids