An Assessment of the Occurrence of Hypothyroidism in Patients Treated With RAI for Hyperthyroidism.

Study Overview
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Brief Summary
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Low RAIU in patients with hyperthyroidism represents a common obstacle in the treatment with RAI. Therefore, a higher dose of RAI must be administered to cure hyperthyroidism in these patients. If we treat patients with thiamazole before starting RAI treatment, serum TSH will rise and result in an increase in iodine uptake by the thyroid gland. By doing so, the dose of RAI to be administered might be lowered to achieve similar therapeutic efficacy. In the past, either calculated or fixed doses of 131I have been used to treat hyperthyroidism. The supposed advantage of a calculated dose compared to a fixed dose is the lowering of hypothyroidism frequency. However, various research papers have contradicted this statement. Antithyroid drugs and RAI therapy have been widely used in the past, either in combination, or independent from one another. This has been done primarily in older patients, to reduce the risk of exacerbation of hyperthyroid symptoms after initiation of RAI. The use of propylthiouracil has been shown to decrease the response rate after RAI due to radioprotective effects. The use of methimazole and carbimazole did not have a negative effect on treatment failure, as long as the medication was discontinued various days before RAI administration. Although this statement is contested in other studies. It is interesting to evaluate retrospective data of patients treated with RAI to evaluate prognostic factors of treatment respons and post RAI hypothyroidism.

Official Title
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An Assessment of the Occurrence of Hypothyroidism in Patients Treated With RAI For Hyperthyroidism, And it's Prognostic Factors.

Conditions
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Nodule Solitary Thyroid, Toxic Multinodular Goiter, Radioactive Iodine-Induced Hypothyroidism

Intervention / Treatment
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* Radiation: radioacive iodine therapy


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Hyperthyroid patients, either subclinical or overt, who have undergone RAI treatment in the period of 2005-2015. Exclusion Criteria: Prior use of L-thyroxine Prior thyroid surgery Prior RAI treatment Patients with thyroiditis

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Toxic Nodule<br>Hyperthyroid patients with underlying toxic nodule | Radiation: radioacive iodine therapy<br>* Hyperthyroid patients who have undergone radioactive iodine treatment to cure them from their hyperthyroidism.<br>|
| Toxic multinodular goiter<br>Hyperthyroid patients with underlying toxic multinodular goiter | Radiation: radioacive iodine therapy<br>* Hyperthyroid patients who have undergone radioactive iodine treatment to cure them from their hyperthyroidism.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The proportion of patients in which hypothyroidism occurs | The proportion of patients in which hypothyroidism occurs after radioiodine treatment | Within 1 year after treatment | 
| The proportion of patients in which hypothyroidism occurs | The proportion of patients in which hypothyroidism occurs after radioiodine treatment | Between 1-2 years after treatment | 
| The proportion of patients in which hypothyroidism occurs | The proportion of patients in which hypothyroidism occurs after radioiodine treatment | Between 2-5 years after treatment |