hypothyroidism
TRANSCRIPT
Told by Dr. Riyaz sir
First hormone disease recorded
There is an axis called hypothalamo-- pituitary --thyroid axis
Hypothalamus produces the thyroid releasing hormone
Pituitary produces TSH
And thyroid produces T3, T4
And a part of reverse T3
T3 is the active form
Whatever T4 is there is converted to T3
All the thyroid hormones have got a negative feed back on TSH
Whenever there is a deficiency of thyroid hormone , TSH will increase
In new born there is a rise and fall of TSH
That is there is an acute surge of TSH in the immediate new born period up to 30 min
It can be as long as 80 min
So when we take the cord blood and do TSH
The “call back rate “ of babies will be more
Which causes more agony to the parents
So people say that it is better to do a filter paper test at least 48 – 72 hours after birth
But it depends upon what is the set up we are working on
And any method of screening is ok
One thing is mandatory is that we should do the screening
And we know that there is a rise in T3 and T4 in the next 24 hours of life
And everything gradually decline and come to normal in the next 2 weeks
And we know that TSH normalizes earlier than T4
Because T4 rises a little later
Any TSH > 20
Any T4 < 6
At anytime
In the immediate new born period
That is something which we have to look again
That doesn’t mean that u have to start therapy on day 1
There is no hurry of starting the treatment
The time limit is 14 days of life
If we start treatment within 14 days of life – the IQ levels will be equal to normal
It depends
Mostly TSH > 40
U can take as 30 , 35 , 40
According to ur experience
If less number of deliveries in ur hospitals u can keep a lower cutoff
If more no. u can keep a higher cutoff
In SAT hospital trivandrum cut off is 20
And keep in mind that it’s a screening program
It is used to find serious cases
We cannot identify 100% with screening
Do not believe on lab normalities
As the TSH normality is different in different age groups
Infancy T4 mean 10.5
1—5 years 10.3
6 – 10 years 9.3
Infancy T4 normal 7.5--- 15.5
TSH 10 in infancy up to 1 year can be taken as normal
TSH beyond infancy up to 5 can be taken as normal
In Obs and gynaec
Tsh cut off 2.5
We do TSH in public health lab trivandrum
By ELISA technique
TSH – 48.9 in new born period
Day 21 (reported late)
Repeat TFT
T4 -6.2
TSH ->60
T3 -0.62
Diagnosis – Congenital Hypothyroidism
So the baby was examined , there was some subtle signs of hypothyroidism like icterus
But no gross features
Thus the importance of screening
Wt gain was low
Child was actually Failing to thrive
So when there is low T4 and T3
And elevated TSH it is Congenital hypothyroidism
It can be of 2 types
1. Permanent
2. Transient – normalizes itself
Transient
Many causes
Transplacental transfer of antibodies
Maternal iodine deficiency
Excess iodine like betadine being painted on child scalp
1. Thyroid dysgenesis – more common
a. Agenesis –athyriosis
b. Hemi agensis – one lobe is not present
c. Ectopic thyroid-
d. Small dysgenetic gland
1. Thyroid dyshormonogenesis- rare
Some enzymes are deficient , gland is normal
Enzyme deficiency is never complete
Produces a little amount of thyroxine
So later presents
So imaging is needed
Image thyroid
So if imaging is abnormal
That is agenesis or dysgenesis
Child needs life long treatment
10 – 15 micrgram of thyroxine
10 for ectopic
Or hemi agensis
15 for complete
If imaging is normal
It is transient or dyshormonogenesis
That child is worth stopping thyroxin trial a 3 years
For 4 weeks
And do TFT
But USG can be misleading too
Better with Tc scan 99
Ideally do Iodine 123 with a per chlorate discharge to know the uptake
High TSH 12.6 at day 6
T4 = normal
No need to start as
Compensated hypothyroidism /
Sub clinical hypothyroidism is not a problem in child(unlike in adult)
In adults subclinical hypo can cause cardiac side effects
Keep him under follow up…when repeated it was normal
Baby escaped unnecessary thyroxine
Thyroid is not that much safe too
It can cause accelerated bone growth
Will have closed AF early
And definitely affects total height and weight
If it is a low T4 and normal TSH ?????
Think about a condition called
Congenital TBG deficiency
Before starting thyroxine to any child
U have to do atleast one free T4 value
Which will be normal in TBG deficiency
TSH and fT4 will be normal
And only T4 will be low in this condition
Congenital TBG deficiency needs no treatment
As the child is euthyroid
Another problem is transient hypothyroxinemia of new born
In low birth weight and pre term baby
As they are keeping the metabolism at a lower rate
So we need not give thyroxin
Only thing that u repeat it 2 – 3 weeks
Always keep in mind another condition
Central hypothyroidism
Though rare it is there
TSH – 0.2
Thought as normal
But it is low …
Low t4
And
Delayed elevation of TSH
In low birth weight and pre term
So in such cases we cannot identify them if we use TSH as the screening test
So repeat screening should be done in preterm and low birth weight babies if possible
Only 10 % of hypothyroidism can be identified clinically by 1 month
At 2 months we can clinically diagnose – 30%
So we miss huge junk if clinically only
Start within 2 weeks
1cm growth with Growth Hormone
– costs 10 000
1 cm growth with thyroxin costs 35
Give it by crushing with mothers milk
In the early morning
Non compliance is common
Do not give iron , calcium or soya along with the thyroid tab
Repeat T4 and TSH after 4 weeks
T4 normalizes at 2 weeks and TSH at 4 weeks
Non compliance is the most common cause for persistent elevation of TSH
Every 2 months till 6 months
Every 4 months till 6months to 3 years
Every 6 months till end of growth
Hearing evaluation should be done in all cases of hypothyroidism as there is an entity called pendredsyndrome
Actually no
Better do only free T4 and TSH
As all of T4 will be converted to T3
One clause is that in early phase of hypothyroidism T3 will be normal(and T4 low) which is of no special use
Our aim is to maintain T4 in the upper half of normal range
Maintain TSH in the normal range
Growth , height , weight should be plotted
And bone age should be noted if any problem
Development should be assessed