Radiation-induced painless thyrotoxic thyroiditis followed by hypothyroidism: a case report and literature review

The utility of I-123 pretherapy scan in I-131 radioiodine therapy for thyroid cancer

BACKGROUND

There is a growing belief that a pretherapy scan yields little or no additional information that would impact on radioiodine ablation dosing. In addition, there is some concern regarding on the stunning effect of a pretherapy scan, especially when I-131 radioisotope is used for imaging. We hypothesized that a pretherapy scan provides invaluable information on the amount of thyroid remnant, sometimes indicating the need for two-step I-131 ablation. It may also detect unsuspected local lymph node involvement or distant metastases, indicating the requirement for a higher I-131 dose after thyroidectomy. The aim of this study was to evaluate how effective pretherapy scans are for guiding I-131 therapy planning and augmenting information provided in the pathology reports for thyroidectomy specimens.

METHODS

We reviewed 122 patients who underwent I-123 pretherapy scan and I-131 radioablation at Yale New Haven Hospital between January 2006 and August 2007. The percentage of neck uptake and whole-body images were acquired 24 hours following the administration of 51.8 MBq (1.4 mCi) of I-123 NaI. A 24-hour uptake of >3% was used as the cutoff to determine whether there was a greater than desired quantity of thyroid remnant, which would require a two-step treatment protocol. Furthermore, attention was paid to identifying cervical lymph nodes, which may not have presented themselves in the euthyroid state at the time of thyroidectomy. Additional clinical information provided by pretherapy scans was computed as percentages with 95% confidence intervals by using adjusted Wald intervals.

RESULTS

Overall, the pretherapy scans provided additional critical information in 25% of the cases (31/122; 95% CI: 18%-34%). For cases demonstrating >3% uptake with midline lymph nodes, the pretherapy scan provided additional information in 50% of the cases (8/16; 95% CI: 28%-72%).

CONCLUSIONS

Our study demonstrated that I-123 pretherapy scans provide valuable information with regard to unsuspected lymph nodes or distant metastases, indicating the requirement for a significantly higher I-131 dose, and unexpected large thyroid remnants, suggesting the need for two-step ablation. We should take advantage of stimulated pretherapy scans and adjust the treatment dosing accordingly.

Acute thyrotoxicosis secondary to destructive thyroiditis associated with cardiac catheterization contrast dye

BACKGROUND

Thyrotoxicosis caused by destructive thyroiditis is self-limited and results from the subacute release of preformed thyroid hormone. Common etiologies include painful subacute thyroiditis and silent (painless) subacute thyroiditis (including postpartum thyroiditis, amiodarone-associated destructive thyroiditis, and lithium-associated thyroiditis). Thyrotoxicosis commonly evolves slowly over a matter of weeks.

PATIENT FINDINGS

We report a unique case of severe thyrotoxicosis caused by acute- onset painful destructive thyroiditis in a patient who received large amounts of nonionic contrast dye Hexabrix® for cardiac catheterization. The results of thyroid function and physical examination were normal before the catheterization.

SUMMARY

The acute onset of severe thyroid pain, rapid increase in serum Free Thyroxine Index, and thyroglobulin concentrations with a triiodothyronine to free thyroxine index ratio of < 20 to 1 were compatible with an acute onset destructive thyroiditis, likely related to direct toxicity from the iodinated contrast material.

CONCLUSIONS

In light of the large number of patients who receive these contrast agents during cardiac catheterization, clinicians should be advised of this potentially serious complication, particularly in the setting of unstable cardiac disease.

Atypical subacute thyroiditis: preliminary observations

Nine patients with painless or minimally painful subacute thyroiditis were seen between late June and October 2000. Six had a history of antecedant viral symptoms. Thyroid peroxidase antibodies were negative in eight patients tested; none had a family history of autoimmune thyroid disease. It is possible that these patients represent examples of postviral painless subacute thyroiditis (atypical subacute thyroiditis). In order to establish the nature of the syndrome, cytological examination, HLA typing, and long-term follow-up are necessary.

Prostate-specific antigen: effect of pelvic irradiation

PURPOSE

To study the effect of pelvic irradiation on the level of serum prostate-specific antigen (PSA).

MATERIALS AND METHODS

Of 33 patients treated with pelvic irradiation to the prostate and seminal vesicles for anal and rectal cancer, 26 received 50.4 Gy or more (1. 8 Gy per fraction), and seven received 25.0 Gy (5.0 Gy per fraction). PSA levels were measured before (n = 33), during (n = 26), and after radiation therapy (n = 33). In 24 patients, follow-up (mean, 15.7 months) PSA data were obtained. Actual and pretreatment PSA levels were compared (Wilcoxon rank test).

RESULTS

During the first 3 weeks in all patients, PSA levels rose steeply, culminating in a 3. 7-fold increase (P =.02). At the end of radiation therapy (7 weeks), the PSA level was no longer significantly different from the pretreatment value. In the long term, the PSA level decreased to 77% of the pretreatment value (P =.04).

CONCLUSION

Irradiation of the prostate initially elevates serum PSA levels. Apparently PSA release is determined by the duration of radiation therapy, while the accumulated dose has a minor effect. In the long term, PSA production is impaired after radical radiation therapy. PSA reference concentrations should be adjusted to these reduced levels.

Anaplastic thyroid cancer with transient thyrotoxicosis: case report and literature review

A 55-year-old woman with anaplastic thyroid carcinoma presented with hyperthyroidism and neck swelling, hoarseness, and cervical lymphadenopathy. On physical examination, she was found to be clinically hyperthyroid with an enlarged, nontender multinodular goitre. Her serum thyroid hormone levels confirmed hyperthyroidism and technetium-99m pertechnetate scan failed to visualize the thyroid gland. Open biopsy showed an invasion of the thyroid gland by anaplastic thyroid carcinoma. The thyrotoxic phase lasted 60 days with predominantly increased thyroxine level and triiodothyronine/thyroxine (T3/T4) ratio decreased below 15. The thyrotoxic period was followed by subclinical hyperthyroidism and hypothyroidism which continued until she died of lung metastasis.