Re: Cytomel & lithium questions

March 5, 2002

> 1//how long are we taking cytomel before going hypo?

> is it 4 weeks? or it can be more!?

It is usually 4 weeks, but it can be more. The key point is that one

needs to be off it for about 2 weeks prior to RAI for TSH to rise to a

level high enough for RAI to be effective.

> 2//question about lithium? i need to know all there is to

> know about lithium,, my endo wants to put me on lithium 2 weeks

> before i 131 to enhances its affect,,any side affects?has anyone

> heard of this before?

We have had some people on the listserv who have taken lithium. Here

is a repost from Dr. Ain regarding this...you might want to look for

the entire study.

***From Dr. Ain***

Lithium does NOT enhance I-131

uptake into tumors. Instead, it enhances I-131 RETENTION in tumors

which have already taken it up. This distinction is important

because lithium is not capable of making a negative I-131 scan into a

positive scan. Rather, some patients with apparently reasonable

uptake of I-131 into their tumors fail to kill these tumors with

I-131 because the tumor discharges the I-131 before an effective

radiation dose is delivered. In these specific cases, lithium can

cause the tumor to retain the radioactive iodine longer and gain

better effect of the administered I-131 dose. I participated in much

of this research and co-authored the most recent study with my NIH

colleagues [Koong SS, Reynolds JC, Movius EG, Keenan AM, Ain KB,

Lakshmanan MC & Robbins JR (1999) Lithium as a potential adjuvant to

131I therapy of metastatic, well differentiated thyroid carcinoma. J

Clin Endocrinol Metab 84, 912-916].

********************

> 3//doctors out there please...is it true if you radiate a tumor

< thyca METs> it wont take RAI,?

I don't know.

> 4// DOSIMETRY? have u heard of it? if so what is it?

Sure....dosimetry is a study to determine how large a dose of RAI can

be safely given to a patient at one time so as not to adversely effect

the bone marrow. There are safey parameters that it has to meet so

that the patient can have a high single dose which may be more

effective treat than several smaller doses. The safety parameters are

specific....maybe one of the Drs. or Ian will post what they are.

Marilyn

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