Hypothyroidism

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