Re: Pregnancy and Breastfeeding around Thyca Treatment

[Guest guest]

Elaine

> However, it got me thinking, I was told that the ablative RAI

> actively works to kill thyroid cells for a year.

Not quite true, the key word here is 'actively'. The RAI stays in the thyroid

tissuefor a period of time and 'actively' destroys it during this time.

Think of it like a house fire. The rate of destruction starts from zero at

the beginning and reaches a maximum at an hour or so (RAI, about 48h). After

this the fire gradually subsides but continues destruction for another 24h

(RAI, about 1 week). After this, there are a few smouldering heaps that go on

for another day or so (RAI, another week). After this, there is the clear up.

Removing the rubble, (RAI, perhaps 2 or 3 weeks), then repairing the damage

to the neighbours (Mr & Mrs Thyca live very close to their neighbours). I

can't comment on the accuracy of the 1 year value, but the whole thing does

take months to stabilise, while the 'active' period is only a couple of

weeks.

Ian

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...

[Guest guest]

Hi Elaine,

I'm not Ian but I think of it this way, iodine (and, thus, RAI) likes to stick

to thyroid tissue. Once it's hanging out in the thyroid tissue, the half

lives apply. That means every 8 days, it's half as radioactive as it was at

the beginning of the 8 days. So there will be miniscule but active amounts of

RAI for quite a long time.

If you have no thyroid tissue, the iodine has no where to stick so it washes

through your body. That means the half lives don't apply and you're rid of

the RAI very quickly.

I think that's why your doctors think it's safe to become pregnant after the

scan IF your're clean.

Hope that helps.

Betty

mailto:bettyy@...

On Thu, 7 Nov 2002 07:03:15 -0800 (PST) elaine alexander

wrote:

>

> Ian,

> Thanks for explaining! I know they told me

> that people have gotten pregnant after RAI

> sooner than they were supposed to, but that

> there was risk of damaging the baby's thyroid.

>

> Is the RAI you get with 1 year scan less

> dangerous? (since it is a smaller dose and

> different isotope)

> Elaine

[Guest guest]

Hi Elaine,

I'm not Ian but I think of it this way, iodine (and, thus, RAI) likes to stick

to thyroid tissue. Once it's hanging out in the thyroid tissue, the half

lives apply. That means every 8 days, it's half as radioactive as it was at

the beginning of the 8 days. So there will be miniscule but active amounts of

RAI for quite a long time.

If you have no thyroid tissue, the iodine has no where to stick so it washes

through your body. That means the half lives don't apply and you're rid of

the RAI very quickly.

I think that's why your doctors think it's safe to become pregnant after the

scan IF your're clean.

Hope that helps.

Betty

mailto:bettyy@...

On Thu, 7 Nov 2002 07:03:15 -0800 (PST) elaine alexander

wrote:

>

> Ian,

> Thanks for explaining! I know they told me

> that people have gotten pregnant after RAI

> sooner than they were supposed to, but that

> there was risk of damaging the baby's thyroid.

>

> Is the RAI you get with 1 year scan less

> dangerous? (since it is a smaller dose and

> different isotope)

> Elaine

[Guest guest]

Hi Betty

> I'm not Ian but I think of it this way, iodine (and, thus, RAI) likes to stick

> to thyroid tissue. Once it's hanging out in the thyroid tissue, the half

> lives apply. That means every 8 days, it's half as radioactive as it was at

> the beginning of the 8 days. So there will be miniscule but active amounts of

> RAI for quite a long time.

This isn't strictly correct. We tend to think hard about the thyroid taking

up iodine - but it puts it out as well (otherwise it would get pretty full

after a few years!)

I have to say that this is not an area that I know much about, so treat my

comments below with some suspicion.

The iodine is secreted by the thyroid in the form of T3 and T4 hormones, and

perhaps other 'iodinated' substances. Clearly, to maintain a balance it needs

to excrete - on average - the same amount as it takes up.

If my memory serves, the effective half-life for RAI in the thyroid (a

combination of the radioactive half life and the physiological half life) is

about 3 or 4 days.

For thycans, this value may be more variable than for the general public

because thyroid metabolism may be quite different. We know about iodine

resistant thyca, there could be the opposite type for all I know.

I remember a complicated discussion about this (about 20 years ago) in which

the consultants were discussing how quickly the TSH levels could be dropped

after maximum RAI uptake in order to stop the thyroid remnant from excreting

any of the RAI - ie to 'lock'it in. There were many difficulties and I don't

think that they came to a concensus.

Ian

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...

[Guest guest]

Hi Betty

> I'm not Ian but I think of it this way, iodine (and, thus, RAI) likes to stick

> to thyroid tissue. Once it's hanging out in the thyroid tissue, the half

> lives apply. That means every 8 days, it's half as radioactive as it was at

> the beginning of the 8 days. So there will be miniscule but active amounts of

> RAI for quite a long time.

This isn't strictly correct. We tend to think hard about the thyroid taking

up iodine - but it puts it out as well (otherwise it would get pretty full

after a few years!)

I have to say that this is not an area that I know much about, so treat my

comments below with some suspicion.

The iodine is secreted by the thyroid in the form of T3 and T4 hormones, and

perhaps other 'iodinated' substances. Clearly, to maintain a balance it needs

to excrete - on average - the same amount as it takes up.

If my memory serves, the effective half-life for RAI in the thyroid (a

combination of the radioactive half life and the physiological half life) is

about 3 or 4 days.

For thycans, this value may be more variable than for the general public

because thyroid metabolism may be quite different. We know about iodine

resistant thyca, there could be the opposite type for all I know.

I remember a complicated discussion about this (about 20 years ago) in which

the consultants were discussing how quickly the TSH levels could be dropped

after maximum RAI uptake in order to stop the thyroid remnant from excreting

any of the RAI - ie to 'lock'it in. There were many difficulties and I don't

think that they came to a concensus.

Ian

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...

[Guest guest]

Elaine

> I know they told me that people have gotten pregnant after RAI sooner than

they were supposed to, but that there was risk of damaging the baby's

thyroid. > Is the RAI you get with 1 year scan less dangerous? (since it is

a smaller dose and different isotope) > Elaine

I can't remember when the fetal thyroid starts developing, but you'd be hard

put to get pregnant so soon after RAI that there would still be enough RAI

around to damage the baby's thyroid. I believe that a mother's hyponess could

affect the developing fetus during certain critical stages, but others here

are better equipped to answer this.

The dose size is a most important factor in determining the risk, but I don't

think that it is a real issue - you should not get pregnant when there is any

RAI in your system. This is an issue for discussion between thyroid experts

and baby experts. From my perspective (radiation safety alone) I would say

that 2-3 months is a starting point and anything less than this carries a

very real risk of fetal harm.

If you have a different isotope for your 1 year scan, and if that isotope is

123I, then that 2-3 months becomes 1 week. However, there has been much

debate about the usefulness of 123I. Also, after 1 week you will still be

very hypo so you should discuss the whole issue with the people who really

know.

Ian

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...

[Guest guest]

Elaine

> I guess it never ceases to amaze me the conflicting opinions of the medical

> community! Decision making is a challenge knowing that people differ so

> much.

Here's what I wrote before on the differences of opinion in the medical

community:

=====================

The reasons for the different treatment protocols is not necessarily that the

medical community cannot agree (although there is a necessary element of

this), but that there is less, in practice, to choose between the treatments

than you might think.

If you look out of the window at the nearest road you will see a huge range

of cars going past. Many of the buyers of those cars will have had a fairly

similar specification when they bought the things - to work and back,

shopping runs, carting kids around etc. Yet they all bought different things

for, often, strange reasons. A week or so ago I witnessed a HUGE man getting

out of a tiny car next to a minuscule woman climbing down from a big 4X4.

If you look at it from the opposite direction it makes more sense. None of

these people bought sledges, unicycles, hot air balloons, space shuttles,

submarines, go-karts, pogo sticks .....

The treatment for pap/fol thyca is well-standardized. Over the years all

sorts of protocols have been tested and have fallen by the wayside. What we

are left with is the best so far. The differences you see? Thyca is a slow

worker. If you change a protocol, even in a busy department, it will be years

before you get enough long-term survival statistics to be sure that the

revised protocol is actually better.

From: http://groups.yahoo.com/group/Thyca/message/13806

=====================

100 years ago, the mainstream treatmens for thyca were bloodletting, leeches,

herbal remedies & who knows what else. Medicine moves on because people step

out of the mainstream and try different things, some of which work.

If their ideas are horribly invasive, disfiguring, painful or dangerous then,

despite working, their ideas will probably fall by the wayside. But if the

idea is easy then it is likely to be accepted and will eventually become the

new mainstream.

From: http://groups.yahoo.com/group/Thyca/message/3811

====================================

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...

[Guest guest]

Elaine

> I guess it never ceases to amaze me the conflicting opinions of the medical

> community! Decision making is a challenge knowing that people differ so

> much.

Here's what I wrote before on the differences of opinion in the medical

community:

=====================

The reasons for the different treatment protocols is not necessarily that the

medical community cannot agree (although there is a necessary element of

this), but that there is less, in practice, to choose between the treatments

than you might think.

If you look out of the window at the nearest road you will see a huge range

of cars going past. Many of the buyers of those cars will have had a fairly

similar specification when they bought the things - to work and back,

shopping runs, carting kids around etc. Yet they all bought different things

for, often, strange reasons. A week or so ago I witnessed a HUGE man getting

out of a tiny car next to a minuscule woman climbing down from a big 4X4.

If you look at it from the opposite direction it makes more sense. None of

these people bought sledges, unicycles, hot air balloons, space shuttles,

submarines, go-karts, pogo sticks .....

The treatment for pap/fol thyca is well-standardized. Over the years all

sorts of protocols have been tested and have fallen by the wayside. What we

are left with is the best so far. The differences you see? Thyca is a slow

worker. If you change a protocol, even in a busy department, it will be years

before you get enough long-term survival statistics to be sure that the

revised protocol is actually better.

From: http://groups.yahoo.com/group/Thyca/message/13806

=====================

100 years ago, the mainstream treatmens for thyca were bloodletting, leeches,

herbal remedies & who knows what else. Medicine moves on because people step

out of the mainstream and try different things, some of which work.

If their ideas are horribly invasive, disfiguring, painful or dangerous then,

despite working, their ideas will probably fall by the wayside. But if the

idea is easy then it is likely to be accepted and will eventually become the

new mainstream.

From: http://groups.yahoo.com/group/Thyca/message/3811

====================================

Ian Adam

Radiation Safety Officer

The Institute of Cancer Research

Cotswold Road

Sutton

Surrey

SM2 5NG

Tel: 020 8722 4250

Fax: 020 8722 4300

EMail: iana@...