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Is the RAIU test a good idea?

It seems that every doctor tries to get their thyroid patients to undergo this test in which a "small" amount of radioactive iodine is ingested and the uptake of iodine into the thyroid can be measured.

One member of our group reported that she developed vision problems right after this test.  Upon going to an ophthalmologist, it was determined that she had macular degeneration and was legally blind in one eye.  The macula is the central area of the eye's retina critical to vision. 

I looked into this situation and found sufficient information to make me believe that the radioactive iodine might go to the macula and cause damage there.  I found a study in which patients with macular degeneration were given iodine (non-radioactive) and this resulted in a significant improvement in their vision, especially their color vision.  This indicates that macular degeneration may involve an iodine deficiency.

If iodine is indeed involved in ocular functions, then radioactive iodine would replace some of the normal iodine there.  When the radioactive iodine breaks down, cellular damage from the radioactivity can occur.  Also, it's possible as the radioactive iodine breaks down, the iodine is transformed into an element with a lower atomic weight.  This means that the normal iodine which is supposed to be there has now been replaced by another element.  I would suspect that this would be a problem but more information is needed.

I think it's possible that the RAIU test may damage the vision and am looking into this.  In the meantime, I can't see any reason for undergoing this test.  Doctors use this test to determine how much radioactive iodine to give the patient in RAI.  If you're not going to get RAI,  are the results of this test important?  How are the results going to influence your treatment?  I don't see any benefit.

The RAI-Uptake Test and Scan by Elaine Moore September 3, 2000

Patients who are initially diagnosed with hyperthyroidism are often ordered to have a radioiodine uptake test (RAI-U) or scan. The idea here is that true hyperthyroidism can be distinguished from conditions where patients happen to be taking excess thyroid hormone or have transient thyroiditis due to infections.

Most importantly, the docs want to know if the patient has Graves' disease, or autoimmune hyperthyroidism, which is responsible for more than 90% of all cases of hyperthyroidism in the West. Why is the RAI-U no longer needed? A blood test for stimulating TSH receptor antibodies is more specific and it doesn't expose the patient and his or her already stressed thyroid to excess radioiodine.

Because the RAI-U is seldom properly explained, many hyperthyroid patients are confused and think they're receiving radioiodine ablation to destroy their thyroids. The RAI-U has a similar principle but a smaller amount of a different isotope is used for the diagnostic test. For ablation, I-131 is usually used, and for the RAI-U, I-125 is used.

For both the test and the ablative procedure, radioiodine is given orally as a dose or drink. In the test, however, the amount of radioiodine taken up by the thyroid gland is measured by an imaging test after any period of time from 2-24 hours. At the same time, a scan is done to show how the iodine is distributed throughout the gland. In Graves' disease, the uptake is high and the pattern of the scan is diffuse. In the case of nodules, there will be spots in the scan with differences in density.

The normal range for the RAI-U is 8% to 35% although the ranges are different in various geographic locations, relative to dietary iodine concentrations. Some researchers say that with the increased iodine content of the American diet, the RAI-U no longer shows clear abnormalities.

RAI-U is increased in hyperthyroidism, iodine deficiency, pregnancy, hydatidiform mole, recovery phase of subacute thyroiditis, rebound after TSH suppression, rebound phase after withdrawal of strong iodine solution or anti-thyroid drugs if the TSH is elevated, therapeutic lithium and inborn errors of thyroid hormonogenesis. From this list, it's clear that the RAI-U is not a specific test for diagnosing Graves' disease. In fact, in patients with T3 thyrotoxicosis, the value may be decreased. The test for stimulating TSH receptor antibodies or TSI is diagnostic for Graves' disease.

There are several sources of error for the RAI-U, most significantly iodine contrast dyes used in imaging studies. These may interfere with test results for several months. Excess dietary iodine in the form of kelp or as inorganic iodine in multivitamins also skewers the results.

And according to John Gofman, a physician and doctor on nuclear/physical chemistry, the radioiodines in diagnostic procedures are just as hazardous as the radioiodine used as an ablative treatment. Gofman cautions that the effects of ionizing radiation on chromosomes in stem cells may take more than 30 years to emerge.

Most docs prefer the RAI-U test. After all it's done locally (often at the clinic at the doctor's office, generating revenue for the clinic) and results are generated quickly, compared to the blood test which usually needs to be sent to a national reference lab and takes several days for results. However, the blood test is superior for diagnosing Graves' disease as well as a safer approach.

Following is my reply to a father whose 12 year-old daughter experienced a sudden decline in vision following a RAIU test. He wanted to know what to ask the ophthalmologist when he took his daughter to see him.


It does sound like your daughter has Graves'/hyperthyroidism. Age 12-14 is the age when girls get it. When they start their periods, the extra blood loss can push the ones with marginal copper status over the edge into enough deficiency to cause hyperT. Doctors don't know anything about this and since they think they know everything they won't listen either.If you give her some copper she will probably recover pretty fast.

The RAIU--eyesight problem is very speculative at this point. But if the radioiodine did cause the problem, then there will probably be some indication of macular degeneration. Have the ophthalmologist check her for macular degeneration. I wouldn't say anything about suspecting radioiodine as the cause beforehand, but ask him afterward if there is any possible reason to suspect a connection. Generally doctors don't want to get into a situation where their diagnosis might suggest that another doctor is guilty of malpractice. They all work to protect each other like fraternity brothers.

Most likely you'll never know if there is a connection, but if we can collect enough cases where vision has suddenly deteriorated after RAIU, we might get someone to investigate a possible cause and effect relationship. 

Ok--I just did a PubMed search and came up with some things. It looks like there is a condition called radiation retinopathy which is a deterioration of the central retina (probably the macula) following radiation treatment. There are thousands of studies about radiation retinopathy, so it must be a well known condition. I looked up radiation retinopathy and Graves and came up with some pertinent studies. 

The first one below indicates that the radiation retinopathy was the result of an excess amount of radiation given to the patient. This suggests that you need to go back to the radiation lab and have someone other than the persons involved check to see if your daughter was mistakenly given more radiation than she was supposed to get.

Later down the page you'll see a study where patients with age-related macular degeneration recovered some visual acuity after ingesting (or bathing in) iodine water. This is why I suggested giving your daughter iodine for her eyes. You'll need copper first so the iodine doesn't aggravate the hyper symptoms.

So when you go to the ophthalmologist, ask if she has retinopathy. Then subsequently if the answer is yes or maybe, ask if it could be radiation retinopathy since it occurred right after a RAIU test. Also, we had another group member who had the RAIU test and had diminished vision right afterward to the point of being declared legally blind in one eye.

As I stated above, I really think there is some connection between the radiation and the vision problems observed right afterward. I hope we can get more evidence that the RAIU test is a possible cause. Best wishes, John

Arch Ophthalmol 1984 Oct;102(10):1473-6 Related Articles, Books, LinkOut 

Radiation retinopathy after orbital irradiation for Graves' ophthalmopathy.

Kinyoun JL, Kalina RE, Brower SA, Mills RP, Johnson RH

Recent reports indicate that orbital irradiation for Graves' ophthalmopathy is sometimes beneficial, particularly for dysthyroid optic neuropathy, and is not associated with serious complications. We are aware, however, of four patients who were found to have radiation retinopathy after orbital irradiation for Grave's ophthalmopathy. All four patients have decreased central acuity, and three of the four are legally blind in one or both eyes. Computer reconstruction of the dosimetry, based on computed tomography and beam profiles, shows that errors in dosage calculations and radiotherapy technique probably account for the radiation retinopathy in three of the four patients. Radiotherapy for Graves' ophthalmopathy should be administered only by competent radiotherapists who are experienced in the treatment of this disease. Similar errors in dosage calculations and treatment techniques may account for other reports of radiation retinopathy after reportedly safe dosages.

Ophtalmologie 1990 May-Jun;4(3):229-31 Related Articles, Books, LinkOut 

[Maculopathy caused by irradiation in patients treated for choroid melanoma].

[Article in French]

Haye C, Desjardins L, Bouder P, Schlienger P, Dorval T

Institut Curie, Paris.

We are using Cobalt 60 plaques at Curie Institute since 1968 for the treatment of malignant choroidal melanoma. We reviewed a series of 79 patients treated between 1982 and 1984 with a minimal follow up of 5 years. Tumors thickness varies between 2 and 11 mm with a mean thickness of 5.7 mm. All the tumors received at least 70 grays at the apex. 7 patients died from other cause, 7 patients presented metastasis 65 patients are alive and well, 49 of them have kept their eye and 16 have been enucleated. 18 patients have a visual acuity below 20/200 because of severe maculopathy, 29 patients have a visual acuity between 20/200 and 20/25. The most severe functional visual loss was due to maculopathy. It consisted of obliteration of the capillaries, exsudation and cystoid macular oedema. If we compare these results to other authors we see that maculopathy is a frequent problem with cobalt 60. For these reasons, we intend in the future to use iodine 125 plaques and prothontherapie that should give us better functional results.

Arch Ophthalmol 1999 May;117(5):609-14 Related Articles, Books, LinkOut 

Radiation retinopathy following plaque radiotherapy for posterior uveal melanoma.

Gunduz K, Shields CL, Shields JA, Cater J, Freire JE, Brady LW

Oncology Service, Wills Eye Hospital, Thomas Jefferson University, Philadelphia, PA 19107, USA.

OBJECTIVE: To identify the risk factors that lead to the development of radiation retinopathy following plaque radiotherapy for posterior uveal melanoma. Radiation retinopathy is a slowly progressive, occlusive vasculopathy characterized by radiation-induced endothelial damage. METHODS: Review of the medical records of patients with posterior uveal melanoma treated with plaque radiotherapy. RESULTS: Of 1300 patients with posterior uveal melanoma treated with plaque radiotherapy from July 1, 1976, through June 30, 1992, radiation retinopathy developed in 560 (43.1%). By using Kaplan-Meier survival estimates, we found that 5% of the patients had nonproliferative radiation retinopathy at 1 year (95% confidence interval [CI], 3%-6%) and 42% at 5 years (95% CI, 38%-45%). The proportion of patients with proliferative retinopathy was 1% at 1 year (95% CI, 0.2%-1.5%) and 8% at 5 years (95% CI, 5%-10%). Multivariate analyses showed that the subset of clinical variables best related to the development of nonproliferative radiation retinopathy were tumor margin of less than 4 mm from foveola (P<.001), tumor limited to the choroid (P = .002), and radiation dose rate of greater than 260 cGy/h to the tumor base (P = .02). The best subset of independent variables related to the development of radiation maculopathy were tumor of less than 4 mm to foveola (P<.001) and the use of radioisotope iridium 192 (192Ir) (P = .02) compared with iodine 125 (125I). From a multivariate model, the most important factors for the development of proliferative radiation retinopathy included diabetes mellitus (P = .01), radioisotope 192Ir (P = .01) compared with 125I, and tumor base of greater than 10 mm (P = .02). CONCLUSIONS: Radiation retinopathy is a common finding after plaque radiotherapy for choroidal melanoma, occurring in 42% of patients at 5 years. The main predictors of radiation retinopathy are posterior tumor location with margin near the foveola and high radiation dose rate to the tumor base.

Noble KG. Related Articles 

Central retinal artery occlusion: the presenting sign in radiation retinopathy.
Arch Ophthalmol. 1994 Nov;112(11):1409-10. No abstract available.
PMID: 7980127

Miller ML, Goldberg SH, Bullock JD. Related Articles 

Radiation retinopathy after standard radiotherapy for thyroid-related ophthalmopathy.
Am J Ophthalmol. 1991 Nov 15;112(5):600-1. No abstract available.
PMID: 1951605

Nikoskelainen E, Joensuu M. Related Articles 

Retinopathy after irradiation for Graves' ophthalmopathy.
Lancet. 1989 Sep 16;2(8664):690-1. No abstract available.
PMID: 2570949

Ophthalmologica 1992;205(2):100-4 Related Articles, Books, LinkOut 

[Changes in Contrast Sensitivity after Iodine Treatment in Bad Hall in Patients with Age-Related Maculopathy].

[Article in German]

Rieger G

Augenabteilung des Paracelsus- Institutes des Landes, Oberosterreich in Bad Hall.

After a cure with iodine in Bad Hall (Upper Austria), patients with age-related maculopathy repeatedly reported improvement in visual power: the picture seen seems to be clearer on the whole or more distinct. These statements were checked in 50 patients with beginning age-related macula degeneration ('dry form') using the 'Vision Contrast test system (VCTS 6500)'. The analysis of the results showed that there is indeed a statistically highly significant improvement in contrast sensitivity after the cure (p < 0.0001). The spontaneous observations of the patients were therefore confirmed by the study.

PMID: 1475080