Hypo after RAI?
The interesting questions below, have recently been posted at thyroid Forum. We have though it could be helpful to bring them here, with our reply, for visitors of this site having similar queries.
"RAI will cure Graves, as it destroys the thyroid. However, most people become hypoT after a few years, and there is no cure for this--just meds to take for life. Maybe some people do not become hypoT --I would be interested to know how this could be, as RAI destroys the thyroid. Maybe in some people some of the gland is still functioning? Can anyone explain this to me? AJ"
Radioactivity only mutates and lately kills cells, so regretfully radiation doesn't cure anything. It's only mutagenic, manymutations leading to cancers. One can ask, why is it then used against cancer when it actually produces it?. Because of its stochastic effects. And what does this mean?. Stochastic effects are effects that occur on a random basis with its effect being independent of the size of dose. The effect typically has no threshold and is based on probabilities, with the chances of seeing the effect increasing with dose. Cancer is thought to be a stochastic effect. So doctors use *high* doses of radioactivity against a tumour, considering that this will surpass the stochastic effects.
Graves' is not cured with RAI either. It destroys, damages tissue, thus with less thyroid cells to produce hormones, fewer hyper symptoms. This is what doctors think, …as they also think that afterwords "hypo is easier to control", "one pill a day and you'll be OK", "T4 is exactly the same hormone your body produces" and finally "it's all in your head".
These are official medical DOGMAS that we, yatrogenic (i.e. medically caused) hypothyroid know by heart. They’re often used by NUMBers doctors, i.e. those who faithfully believe in thyroid hormone panels, rather than believing in how the person is doing.
So, doses used for Graves' don't ablate the gland, like in thyroid cancer where higher doses are given, but partially destroy its tissues. The destruction is achieved with beta particles and high energy gamma radiation emitted by I-131 on its decay.
And the amount of tissue actually destroyed depends on several factors:
- iodine uptake by the gland
- bulk of tissue to be destroyed
- length of time radioactive iodine is retained in the gland
- distribution within the tissue
- radio-sensitivity of thyroid cells
- high iodine diet can interfere
- different opinions regarding thyroid blockers role
- degree of hyperthyroidism, etc
Many factors depend on the characteristics of the gland, that differ among individuals. Given dose is also important, because it's often very badly calculated. How many people have an eco-doppler color study done prior RAI?. Almost nobody!. How many have a iodine uptake prior RAI to fine tune dose? .Very few. More often than not, doses are given on an "estimation" basis upon a supposed weight of gland. And there are even two or three protocols, depending on the dose, but there are a number of doctors who opt for dosing at large to ensure quick hypothyroidism.
Among those who use lower doses, RAI doesn't instantaneously eradicate the thyroid. It's a process that continues to progress over several years. There may be a small number of patients that don't become hypothyroid immediately, but it's been proven that, within 10 years after RAI, 100% of RAI'ed people is hypothyroid.
We know of some persons who feel better 1, 2 or 3 years after RAI, specially because they feel relieved from hyper symptoms. We don't want to rain over other's parade, but as soon as hypothyroidism is present, most of them invariably miss and long for their old hyper days.