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Hyperthyroidism, Low Uptake, Negative Ab

Last Updated: · Doctors

Question 1

Thanks for you site.I will greatly appreciate your --.Clinical problems

PATIENT 1. Young female.Symtoms of thyrotoxicosis , no eye signs ,no grossly enlarged thyroid gland , or bruit,T4 = 50 ;TSH = < 0.03

Referred for I-131.Thyroid scan done = Uniform uptake of TC. Calculated uptake = 2 % , Gland not grossly enlarged.Not convinced that patient is actually Graves disease , I put patient on neomercazole. Repeat testing approximately 6 weeks later .T4 = 18.6 T3 = 9.9 TSH < 0.03 ANTIBODIES -VE

Referring doctor incist on I-131

  1. Should I administer the I-131
  2. Is there a cutoff level on the TC uptake scan that defines Graves disease from other, if so what is it , some text claims 5 % , some says 20 %. If I look at the diagram in the website it appears that the the scan does not play much of a role .
  3. Strictly speaking , should the scan have been done .
  4. How should patients be managed with prolonged symptoms of hyper-tyroxemia ,clearly of thyroid origin , (as the thyroid does show up on the scan), but the level of uptake does not appear clearly to be of a thyroditis( I am under the impression that a thyroid does not show up in the more common thyroditis , -but the level of uptake does not appear that clearcut of a Graves disease .
  5. What is the role of antibody testing in this general scenario , and for that matter a Thyroid FNA or biopsy (no nodules palpable )

Response 1

The three diagnoses that come to mind are 1) Graves' disease with an iodide load suppressing thyroid uptake, 2)"painless thyroiditis" of the Hashimoto's variety, and 3) subacute thyroiditis, which can also be painless. You could measure urinary iodide. Obviously there are other possibilities but less likely. If both TG and TPO antibodies were negative, that is against #1 or #2, but not conclusive.Possibly measuring anti TSH-Receptor antibodies would be helpful.High ESR or CRP might have been helpful to suggest SAT. A biopsy might be diagnostic, but usually is not needed. You have time on your side, and the patient is not now in danger. I personally would not give RAI at this time. By the way, it is difficult to judge the tests in the absence of normal values.

It is not sure whether you describe 2% TeCO4 uptake, or iodide uptake. I am only familiar with RAIU in this siuation, and would not want to treat a patient with a low uptake since the diagnosis is obscure, and you would need to give a very large dose to "treat" the thyroid. The scan is usually not helpful in this situation. A scan can easily identify the thyroid even if the isotope uptake is miniscule, because of the sensitivity of the machinery.

What to do? One approach would be, when the T4 is normal, stop the neomercazole, and follow the patient. If hyperthyroidism recurs, check antibodies in aonther lab. Do another RAIU. Test urinary iodide if uptake of I-131 or I-123 is low. Check TRAb and ESR. Get a good dietary history. Was the patient recently pregnant? Find out if the patient had a previous normal thyroid test at some time.Make sure that the patient is not on some drug such as amiodarone. Usually the process wioll become more clear in time, and both #2 and #3 tend to be self-limiting. A list of possible causes of this problem can be found in

L De Groot, MD

Question 2

PATIENT 2. I had a similar 70 year old female.Ab,s ? , referred for I-131. With biochemical and clinical typer thyroxemia for 3 - 4 months, gland not grossly ,significantly enlarged ,with a calculated TC(20 MIN ) uptake of 2 %, Not convinced that she required the I-131 , I opted for neomercazole , the elevated hormone levels dropped , as well as after I stopped the medication . (Was this correct , if the levels did not normalize what should have been done.

Response 2

Most of the above applies here as well. Your approach seems to be logical so far.

L De Groot, MD