Parathyroid adenoma in patients with Graves' disease: a report of 21 cases

Presentation and Surgical Outcomes of Primary Hyperparathyroidism After Radioactive Iodine Therapy

BACKGROUND

Radioactive iodine (RAI) is a common treatment for various thyroid diseases. Previous studies have suggested susceptibility of parathyroid glands to the mutagenic effect of RAI and the development of primary hyperparathyroidism (PHPT). We tested the possible link between prior RAI treatment, disease presentation, and treatment outcomes.

METHODS

A retrospective analysis of 704 individuals who underwent parathyroidectomy for PHPT at a tertiary care center between the years 2015 and 2023 was performed. Preoperative and postoperative parameters, including demographic characteristics, biochemical markers, imaging data, and surgical and pathology findings were collected and analyzed to compare differences in patients who had previous RAI treatment and those who did not (non-RAI). Univariate statistical analyses were performed.

RESULTS

Twenty-nine patients had a history of RAI treatment. Indications for RAI treatment included hyperthyroidism (n = 18), papillary thyroid cancer (n = 6), subacute thyroiditis (n = 1), follicular cancer (n = 1), and toxic goiter (n = 1). Average latency time between RAI exposure and development of PHPT was 18.4 ys. On comparison of the two groups, there was no difference in age, sex, race/ethnicity, day of surgery body mass index, preoperative parathyroid hormone, calcium, glomerular filtration rate, creatinine, vitamin D, or phosphate levels. There was also no difference in preoperative diagnosis of osteoporosis or nephrolithiasis. Postoperatively, there was no difference in parathyroid hormone, calcium, or creatinine levels, or in rate of cure. There was significantly higher chance of unilateral exploration in the operating room (75.9% RAI, 54.1% non-RAI, P = 0.02) and increased rate of single-gland disease in the RAI group, although the latter finding was not statistically significant (79.3% RAI, 65.2% non-RAI, P = 0.12). There was no difference in adenoma size as noted on the pathology report (greatest dimension 1.7 cm RAI, 1.7 cm non-RAI, P = 0.28). Subgroup analysis of the RAI group based on reason for RAI treatment (cancer versus hyperthyroidism) showed no statistically significant differences in the examined demographic or clinical data.

CONCLUSIONS

There does not seem to be a relationship between prior RAI treatment and the clinical presentation of PHPT. Additionally, differences in RAI dose do not appear to be associated with a change in clinical presentation. Our study revalidates that age and latency are inversely related, which is a previously shown finding. Clinicians may be reassured that patients with prior RAI history may not have differences in clinical characteristics, disease presentation, or treatment outcomes.

Primary hyperparathyroidism after radioactive iodine therapy: Is it a distinct clinical entity?

BACKGROUND

Radioactive iodine (RAI) treatment is considered a rare cause of primary hyperparathyroidism (pHPT).

METHOD

A multi-institutional retrospective review of patients with pHPT who underwent parathyroidectomy from 1990 to 2020 was completed to evaluate the prevalence and latency time for development of RAI-associated pHPT and determine clinical differences in pHPT patients with or without prior RAI treatment.

RESULTS

1929 patients with sporadic pHPT underwent parathyroidectomy; 48 (2.5%) had prior RAI treatment and 1881 (97.5%) did not. RAI treatment was for thyrotoxicosis in 43 (90%) patients. Average latency was 24 years (3-59 years) and inversely correlated with age. Patients with prior RAI treatment had lower preoperative calcium and PTH levels (p < 0.0001). No significant differences were observed in age, symptoms, pathology, ectopic glands and cure rate.

CONCLUSION

RAI is a potential causative factor for pHPT, accounting for 2.5% of sporadic pHPT. RAI-associated pHPT may be a less severe form of sporadic pHPT and latency inversely correlates with age.

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.

Parathyroid Changes After RAI in Patients With Differentiated Thyroid Carcinoma

OBJECTIVE

The purpose of this study was to investigate parathyroid hormone (PTH), serum calcium, phosphorus, and 25-hydroxyvitamin D (25-OH-VD) changes before and after radioactive iodine (RAI) in differentiated thyroid carcinoma (DTC) patients at different time points.

METHODS

A total of 259 DTC patients who received RAI were prospectively enrolled. We evaluated PTH, serum calcium, phosphorus, and 25-OH-VD levels at baseline pre-RAI, five days, six weeks, and six months post-RAI, respectively. We analyzed the risk factors of hypocalcemia at five days post-RAI.

RESULTS

The mean PTH, serum calcium and phosphorus values decreased five days post-RAI compared with pre-RAI (PTH 4.18 ± 1.23 pmol/L vs. 3.95 ± 1.41 pmol/L; calcium 2.27 ± 0.09 mmol/L vs. 2.20 ± 0.11 mmol/L; phosphorus 1.25 ± 0.17 vs. 0.98 ± 0.20 mmol/L, P < 0.05), and the differences were statistically significant. The mean 25-OH-VD levels did not significantly decrease at five days post-RAI. 21.2% (55/259) of patients had hypocalcemia at five days post-RAI, and all of them were given oral calcium supplements. At six weeks post-RAI, all of the above parameters were higher than those at five days post-RAI. Multivariate regression analysis showed that baseline pre-RAI serum calcium < 2.27 mmol/L, PTH < 4.18 pmol/L and negative ^99mTcO₄^- thyroid imaging were risk factors for hypocalcemia at five days post-RAI.

CONCLUSION

For DTC patients with normal PTH and serum calcium levels at pre-RAI, their PTH, serum calcium, and phosphorus levels decreased at five days post-RAI. About one-fifth of patients could have hypocalcemia at five days post-RAI. Lower baseline pre-RAI serum calcium and PTH levels and negative ^99mTcO₄^- thyroid imaging were risk factors for hypocalcemia five days post-RAI.

Association of parathyroid carcinoma and thyroid disorders: A clinical review

Parathyroid carcinoma is a rare malignancy, which usually occurs as a sporadic disease, and less frequently in the setting of genetic syndromes. Despite the association of parathyroid and thyroid disorders being quite common, the coexistence of parathyroid carcinoma and thyroid disease is rare. We reviewed the pertinent literature. The terms "parathyroid carcinoma" and "thyroid disease, hyperthyroidism, thyrotoxicosis, hypothyroidism, thyroid nodule(s), Graves' disease, autonomously functioning thyroid nodules" were used both separately and in reciprocal conjunction to search MEDLINE for articles published from January 2007 to March 2016. The search was prompted by the observation of a never reported association of autonomously functioning thyroid nodules and parathyroid carcinoma. Two hundred and twenty-one parathyroid carcinoma patients have been described during the last 10 years. Neck ultrasonography and parathyroid scintigraphy are the most common instrumental studies used in detecting parathyroid lesions. Serum parathyroid hormone and calcium levels are high in the majority of parathyroid carcinoma patients. Only 21 patients with parathyroid carcinoma and thyroid disorders were found. Our patient is the first casual association between parathyroid carcinoma and autonomously functioning thyroid nodules reported in literature and diagnosed using parathyroid and thyroid scintigraphies. Parathyroid carcinoma is a very rare endocrine tumor and association with thyroid disease is not frequent. Parathyroid carcinoma pre-operative diagnosis is often difficult also because available literature data are not homogenous and there is not a common operative guideline. Our case confirms the role of parathyroid scintigraphy, encouraging the association with thyroid scintigraphy, especially in the presence of (multi)-nodular goiter in order to address the most appropriate surgical management.