Parathyroid adenoma after radioactive iodine therapy for multinodular goiter

Hyperparathyroidism subsequent to radioactive iodine therapy for Graves' disease

BACKGROUND

The development of primary hyperparathyroidism (PHPT) after radioactive iodine (RAI) treatment for thyroid disease is poorly characterized. The current study is the largest reported cohort and assesses the disease characteristics of patients treated for PHPT with a history of RAI exposure.

METHODS

A retrospective analysis comparing patients, with and without a history of RAI treatment, who underwent surgery for PHPT.

RESULTS

Twenty-eight of the 469 patients had a history of RAI treatment, all for Graves' disease. Patients with a history of RAI exposure had similar disease characteristics compared to control; however, patients with a history of RAI treatment had a higher rate of recurrence (7.4% vs 1.2%, p = 0.012).

CONCLUSION

PHPT in patients with a history of RAI treatment can be approached in the same manner as RAI naive PHPT patients; however, the risk of recurrence of PHPT in RAI exposed patients may be higher.

The effects of radioiodine therapy on parathyroid function among patients with papillary thyroid cancer: a retrospective cohort study

PURPOSE

To explore the effects of initial radioiodine therapy on parathyroid function among postoperative papillary thyroid cancer (PTC) patients.

METHODS

Postoperative PTC patients who were admitted in our department from April 2018 to April 2019 were recruited. Patients were divided into two groups: Group A, who underwent surgery and initial radioiodine therapy in our hospital, and Group B, who did not receive radioiodine therapy after surgery. The levels of serum calcium, magnesium, phosphorus, parathyroid hormone (PTH), and 25 hydroxyvitamin D3 were collected. Data were analyzed by SPSS 25.0.

RESULTS

A total of 252 patients were included. Between the two groups, no significant difference of PTH in 6th, 9th, and 12th month was found during postoperative follow-up (p = 0.493, p = 0.202, p = 0.814). No significant difference of PTH was found after stratifying Group A according to ¹³¹I dosage (p = 0.751 for 6th month after operation, p = 0.130 for 9th month after operation, p = 0.683 for 12th month after operation), interval time between surgery and radioiodine therapy (p = 0.522 for 3rd day after ¹³¹I therapy, p = 0.184 for 9th month after operation, p = 0.311 for 12th month after operation), and ratio of parathyroid autotransplantation (p = 0.545 for 3rd day after ¹³¹I therapy, p = 0.485 for 6th month after operation, p = 0.201 for 9th month after operation, p = 0.146 for 12th month after operation).

CONCLUSIONS

Initial radioiodine therapy following PTC surgery had no significant adverse effect on parathyroid function in the short term. However, physicians should inform patients of possible risks of abnormal parathyroid function prior to RAI therapy, and parathyroid function was periodically reviewed after RAI therapy.

Effect of radioactive iodine therapy on carotid intima media thickness in patients with hyperthyroidism

OBJECTIVE

The aim of this study was to evaluate the carotid intima media thickness (IMT) in patients with thyrotoxicosis who received radioactive iodine (RAI) treatment.

METHODS

This study was planned to be conducted with two different groups of people. There were 87 patients in the patient group and 98 controls. Participants were evaluated for atherosclerosis risk factors. Mean carotid IMT was measured from three consecutive traces at the common carotid artery bifurcation.

RESULTS

The mean carotid IMT was 0.81 ± 0.20 in patient group and this was higher than the controls (0.68 ± 0.19) (p < 0.01). IM thickening was positively correlated with the applied RAI dose levels in the treatment group (p = 0.029). In patients with only HT, the data of the two groups showed a significant difference, with the average IMT being higher in the patient group than that of the control group (p: 0.011).

CONCLUSION

RAI used in the treatment of thyrotoxicosis increases the IMT of carotid artery independent of age and sex. This treatment yields better results with higher doses, and this effect is more marked in patients with HT. Hence, we believe that it is necessary to calculate the dose properly for hyperthyroid cases in which treatment with RAI is planned. In particular, the patients with HT need to be treated with the minimum possible dose. Further, carotid arteries should be evaluated with US following RAI treatment.

Risk of parathyroid adenomas in patients with thyrotoxicosis exposed to radioactive iodine

External ionizing radiation is a risk factor for primary hyperparathyroidism. Whether exposure to radioactive iodine contributes to the risk of primary hyperparathyroidism is unknown. Patients with thyrotoxicosis are often treated with radioactive iodine and its accumulation in the thyroid gland exposes the adjacent parathyroid glands to radioactivity. Six thousand and eighty two patients with thyrotoxicosis (ICD-9 = 242) were identified from medical records. In a randomly selected subcohort we assessed the frequency of treatment with radioactive iodine to be 86%. The number of patient-years at risk was 77,118. Patients with parathyroid adenomas (ICD-9 = 195.1) were recruited from the Swedish Cancer Registry. Eleven patients with parathyroid adenomas following the diagnosis of thyrotoxicosis were identified. The standard incidence ratio (SIR) compared to the reference population of approximately 900,000 was 1.14 (95% CI 0.57-2.03). The median age at exposure was 59 years and the latency period between diagnosis of thyrotoxicosis and parathyroid adenoma was 7.4 years (range <1-19 years). This study does not indicate that patients with thyrotoxicosis treated with radioactive iodine in adult age have increased risk of developing parathyroid adenoma.

Silent parathyroid adenoma mistakenly interpreted on FDG-PET as thyroid cancer metastasis in a patient with elevated thyroglobulin and negative I-131 whole body scan and removed by radioguided minimally invasive surgery

Detection of recurrent and metastatic thyroid cancer remains a considerable challenge in patients presenting with rising thyroglobulin levels but with negative I-131 whole body scintigraphy. Such is the case in this patient with follicular thyroid cancer in whom subsequent FDG PET scanning showed a solitary hypermetabolic cervical lesion. With definitive management and multidisciplinary approach in mind, radioguided surgical excision came into play through the use of Tc-99m sestamibi, leading to successful removal of the lesion. Histopathology, however, revealed a parathyroid adenoma. This highlights the importance of considering differential diagnoses in apparent cases of recurrence to avoid potential pitfalls.

Hyperparathyroidism after radioactive iodine therapy

BACKGROUND

Radioactive iodine (RAI) treatment has been suggested to cause primary hyperparathyroidism (HPT). We describe a series of patients with HPT and a history of RAI exposure.

METHODS

Patient demographic and clinical information was evaluated, including the latency time to the development of HPT after RAI exposure.

RESULTS

We treated 11 patients with HPT and a history of RAI exposure. RAI treatment was administered for benign thyroid disease in 9 (82%) cases. Thirty-six cases of HPT after RAI exposure in the English literature were compiled for further analysis. In this collective experience, the average latency time to the development of HPT after RAI treatment was 13.5 +/- 9.1 years and was found to be inversely correlated with age at RAI exposure.

CONCLUSIONS

Patients who undergo RAI treatment are at risk of developing HPT, and this risk appears to increase in elderly patients. Serum calcium surveillance is recommended for patients who have undergone RAI treatment.