Parathyroid changes after high dose radioactive iodine in patients with thyroid cancer

Advances in the selection and timing of postoperative radioiodine treatment in patients with differentiated thyroid carcinoma

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. Patients who receive systematic care typically have a better prognosis. RAI treatment plays a key role in eradicating any remaining thyroid lesions in DTC patients, hence decreasing the risk of distant metastases and cancer recurrence. As research continues to advance, RAI treatment is becoming more and more individualized. Because of the excellent prognosis for DTC patients, there is a relatively broad window for RAI treatment, making it easy to overlook when to receive RAI treatment. However, research on this issue can help patients with varying recurrence risk stratification make better decisions about when to begin RAI treatment following surgery, and physicians can schedule patients based on the severity of their disease. This will improve patient prognosis and lessen needless anxiety in addition to helping solve the problems of unjust healthcare resource distribution. In this review, we will mainly discuss the target population of RAI treatment as well as studies that examine the impact of RAI treatment timing on patient outcomes. In an effort to discourage DTC patients and physicians from selecting RAI therapy at random, we also review the possible negative effects of this treatment.

[Review of clinical practice guidelines for hypoparathyroidism]

Hypoparathyroidism is a rare disorder characterized by the absent or inappropriately decreased serum parathyroid hormone in the parathyroid glands, which is accompanied by impaired calcium-phosphorus metabolism.The main etiology of hypoparathyroidism remains damage or removal of the parathyroid glands during neck surgery. In view of the incidence of thyroid cancer, primary hyperparathyroidism and other pathologies of the neck organs, which radical treatment can lead to the parathyroid gland impairment, an increased number of patients with hypoparathyroidism is expected. Autoimmune hypoparathyroidism is the second most common form of the disease, usually occurring as part of type 1 autoimmune polyglandular syndrome. Autoimmune hypoparathyroidism usually occurs in childhood and is characterized by a severe course of the disease, especially in the case of concomitant malabsorption syndrome.Chronic hypoparathyroidism of any etiology requires lifelong multicomponent therapy, as well as careful monitoring and an individual approach to choose the optimal treatment strategy. In the absence of adequate follow-up, the risks of long-term complications significantly increase, particularly in the renal, cardiovascular systems; in the soft tissues and in the brain, it could lead to visual disturbances; pathology of the musculoskeletal system with a decreased bone remodeling and a potential risk of fractures, as well as to the neurocognitive disorders and an impaired health-related quality of life.Timely diagnosis, rational medical therapy and management strategy may reduce the risks of short-term and long-term complications, frequency of hospitalizations and disability of patients, as well as improve the prognosis.This review covers the main issues of Russian guidelines for the management of chronic hypoparathyroidism, approved in 2021, including laboratory and instrumental evaluation, treatment approaches and follow-up. This guidelines also include the recommendations for special groups of patients: with acute hypocalcemia, hypoparathyroidism during pregnancy.

Parathyroid Hormone Level Changes Following Radioiodine Therapy for Thyroid Cancer: A Prospective Observational Study

OBJECTIVE

Our objective was to analyze the effect of radioiodine (RAI) therapy on parathyroid hormone (PTH) secretion.

METHODS

A total of 137 patients were included and divided into 2 groups based on pretherapy PTH levels. The residual thyroid tissue volume was classified into 4 grades (0-3), and a value of 0 indicated that there was no apparent residual tissue. We analyzed the PTH level changes among different time points in each group and the factors that could predict the PTH level changes.

RESULTS

In 113 patients with normal parathyroid gland function, the PTH level at baseline, 1 day, 7 days, 1 month, 3 months, and 6 months after RAI therapy did not show any significant difference; in 24 patients with decreased parathyroid gland function, the level of PTH immediately decreased after the implementation of RAI therapy but gradually returned to a pre-RAI therapy level within 6 months. On the seventh day after therapy, the mean value of PTH in patients with a residual thyroid tissue volume of extent of 0/1 was 8.0 ± 2.3 pg/mL, which was significantly higher than that in patients with a residual thyroid tissue volume of extent of 2/3 (P = .011). Similar phenomena were observed 1 month, 3 months, and 6 months after therapy.

CONCLUSION

RAI therapy had a significant transient adverse effect on parathyroid gland function in patients with decreased PTH secretion pretherapy, and the extent was associated with the amount of residual thyroid tissue.

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.

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.

Delayed Hypoparathyroidism following Thyroidectomy, a Diagnostic Conundrum: A Report of Three Cases from Sri Lanka

Introduction

Hypoparathyroidism, which is a common complication following total thyroidectomy can be transient in majority and permanent in 1.5% of the patients and usually occurs secondary to an inadvertent removal of parathyroid glands, mechanical or thermal injury or disruption of the vasculature. In some patients, it is observed that symptoms of hypocalcemia can occur for the first time several years after the surgery, which is known as “delayed hypoparathyroidism.” We report three cases of delayed hypoparathyroidism from Sri Lanka, presenting several years after total thyroidectomy. Case Presentation. Case 1- a 60-year-old Sri Lankan woman who presented with symptomatic hypocalcemia for the first time, 30 years after total thyroidectomy for follicular thyroid carcinoma. Case 2- a 53-year-old Sri Lankan woman presenting with neuropsychiatric manifestations of hypocalcemia for the first time, 12 years after total thyroidectomy for papillary thyroid carcinoma. Case 3- a 49-year-old Sri Lankan woman developing symptoms of hypocalcemia for the first time, 11 years after completion of thyroidectomy for papillary thyroid carcinoma. All these patients were detected to have low parathyroid hormone levels, without an alternative etiology for hypoparathyroidism, hence leading to a diagnosis of delayed post-thyroidectomy hypoparathyroidism.

Conclusion

Delayed hypoparathyroidism is a rare phenomenon, which is secondary to progressive atrophy of parathyroid glands and slowly progressive hypovascularization of parathyroids due to scar tissue retraction following thyroidectomy. The nonspecific nature of hypocalcemic symptoms and lack of continuous follow-up for a long time after thyroidectomy could contribute to a further delay in diagnosis. However, it is an important diagnosis to consider in any patient with a history of neck surgery presenting with hypocalcemia, irrespective of the time duration of surgery, as timely diagnosis and treatment can prevent long-term complications of hypocalcemia and improve the quality of life.

Idiopathic Hypoparathyroidism With Papillary Thyroid Carcinoma in a Young Male: A Rare Case Report

BACKGROUND

Idiopathic hypoparathyroidism (IHP) is a rare disorder that is diagnosed by excluding other possible etiologies. Thyroid surgery causes approximately 14-60% of all cases of hypoparathyroidism; of these, surgery for papillary thyroid carcinoma (PTC) is the most common reason. Here, we report an extremely rare case of IHP combined with PTC.

CASE PRESENTATION

A 22-year-old man presented with a history of uncontrollable extremity and facial numbness, spasm and twitch lasting for nine years. He had been misdiagnosed with epilepsy and gained no relief from antiepileptic therapy. The laboratory evaluation revealed reduced parathyroid hormone and serum calcium and elevated inorganic phosphorus. After considering IHP, ultrasound detected a solid hypoechoic and irregularly shaped nodule 13×8×9 mm in size in the upper pole of the right thyroid gland, and fine-needle aspiration biopsy indicated PTC. Then, the patient underwent surgical treatment and radioactive iodine ablation. The long-term treatment strategy consisted of oral levothyroxine for thyroid-stimulating hormone inhibition and oral calcium and vitamin D supplements for hypocalcemia control.

CONCLUSION

We report a rare case of IHP combined with PTC in a 22-year-old male. Some experiences and lessons from our treatment procedure merit discussion, and we hope that our report can serve as a reference for the diagnosis and treatment of similar patients in the future.

Standards of care for hypoparathyroidism in adults: a Canadian and International Consensus

PURPOSE

To provide practice recommendations for the diagnosis and management of hypoparathyroidism in adults.

METHODS

Key questions pertaining to the diagnosis and management of hypoparathyroidism were addressed following a literature review. We searched PubMed, MEDLINE, EMBASE and Cochrane databases from January 2000 to March 2018 using keywords 'hypoparathyroidism, diagnosis, treatment, calcium, PTH, calcidiol, calcitriol, hydrochlorothiazide and pregnancy'. Only English language papers involving humans were included. We excluded letters, reviews and editorials. The quality of evidence was evaluated based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. These standards of care for hypoparathyroidism have been endorsed by the Canadian Society of Endocrinology and Metabolism.

RESULTS

Hypoparathyroidism is a rare disease characterized by hypocalcemia, hyperphosphatemia and a low or inappropriately normal serum parathyroid hormone level (PTH). The majority of cases are post-surgical (75%) with nonsurgical causes accounting for the remaining 25% of cases. A careful review is required to determine the etiology of the hypoparathyroidism in individuals with nonsurgical disease. Hypoparathyroidism is associated with significant morbidity and poor quality of life. Treatment requires close monitoring as well as patient education. Conventional therapy with calcium supplements and active vitamin D analogs is effective in improving serum calcium as well as in controlling the symptoms of hypocalcemia. PTH replacement is of value in lowering the doses of calcium and active vitamin D analogs required and may be of value in lowering long-term complications of hypoparathyroidism. This manuscript addresses acute and chronic management of hypoparathyroidism in adults.

MAIN CONCLUSIONS

Hypoparathyroidism requires careful evaluation and pharmacologic intervention in order to improve serum calcium and control the symptoms of hypocalcemia. Frequent laboratory monitoring of the biochemical profile and patient education is essential to achieving optimal control of serum calcium.

Medical Hypoparathyroidism

Hypoparathyroidism is a metabolic disorder characterized by hypocalcemia, hyperphosphatemia, and inadequate levels of or function of parathyroid hormone (PTH). The authors review the nonsurgical or medical causes of hypoparathyroidism. The most common of the nonsurgical causes is autoimmune destruction of the parathyroid. Magnesium deficiency or excess can cause a functional hypoparathyroidism. Genetic conditions result in hypoparathyroidism as part of a syndrome or in isolation. Pseudohypoparathyroidism reflects a resistance to PTH. Infiltrative, metastatic, radiation destruction, mineral deposition, or idiopathic are uncommon causes of hypoparathyroidism. This article reviews the causes of hypoparathyroidism and an approach to the evaluation of this condition.

Time to parathyroid function recovery in patients with protracted hypoparathyroidism after total thyroidectomy

OBJECTIVE

Hypocalcaemia is the most common adverse effect after total thyroidectomy. It recovers in about two-thirds of the patients within the first postoperative month. Little is known, however, about recovery of the parathyroid function (RPF) after this time period. The aim of the present study was to investigate the time to RPF in patients with protracted (>1 month) hypoparathyroidism after total thyroidectomy.

DESIGN

Cohort prospective observational study.

METHODS

Adult patients undergoing total thyroidectomy for goitre or thyroid cancer. Cases with protracted hypoparathyroidism were studied for RPF during the following months. Time to RPF and variables associated with RPF or permanent hypoparathyroidism were recorded.

RESULTS

Out of 854 patients undergoing total thyroidectomy, 142 developed protracted hypoparathyroidism. Of these, 36 (4.2% of the entire cohort) developed permanent hypoparathyroidism and 106 recovered: 73 before 6 months, 21 within 6-12 months and 12 after 1 year follow-up. Variables significantly associated with RPF were the number of parathyroid glands remaining in situ (not autografted nor inadvertently resected) and a serum calcium concentration >2.25 mmol/L at one postoperative month. Late RPF (>6 months) was associated with surgery for thyroid cancer. RPF was still possible after one year in patients with four parathyroid glands preserved in situ and serum calcium concentration at one month >2.25 mmol/L.

CONCLUSIONS

Permanent hypoparathyroidism should not be diagnosed in patients requiring replacement therapy for more than six months, especially if the four parathyroid glands were preserved.

Effect of 131I 'clear residual thyroid tissue' after surgery on the function of parathyroid gland in differentiated thyroid cancer

Thyroid cancer is a common malignant tumor of the endocrine glands. Although surgery is the optimal treatment utilized, the disease is characterized by recurrence and metastasis. The aim of the present study was to determine the effect of iodine-131 (¹³¹I) ‘clear residual thyroid tissue’ following surgery on the treatment of differentiated thyroid cancer (DTC) and its effect on the function of the parathyroid gland. A total of 160 patients diagnosed with DTC, who were consecutively admitted to our Hospital between June 2012 and June 2014 and underwent total thyroidectomy or subtotal resection, were included in the present study. After three months, the patients were administered ¹³¹I ‘clear residual thyroid tissue’ treatment and underwent a whole body scan after 1 week to determine whether ‘clear residual thyroid tissue’ treatment was successful or not. The treatment was repeated within 3 months if not successful. Of the 160 patients, 24 patients had cancer metastasis (15.0%). The average dose of ¹³¹I used for the first time was 6.4+1.2 GBq and the treatment was successful in 66 cases (41.3%). The average treatment time was 2.8±0.6 therapy sessions. The results showed that, prior to and following the first treatment and at the end of the follow up, levels of the parathyroid hormone, serum calcium and phosphorus were compared, and no statistically significant difference (P>0.05) was observed. There were 5 patients with persistent hypothyroidism and 8 patients with transient hypothyroidism. The levels of thyroglobulin were significantly decreased, and the difference was statistically significant (P<0.05). A total of 48 patients (30%) with hypothyroidism were identified. In conclusion, the results have shown that DTC resection and ¹³¹I ‘clear residual thyroid tissue’ treatment did not significantly impair the parathyroid function, thereby improving the treatment effect.

Graves' Disease, Hypoparathyroidism, Systemic Lupus Erythematosus, Alopecia, and Angioedema: Autoimmune Polyglandular Syndrome Variant or Coincidence?

Data on coexisting Graves' disease (GD), hypoparathyroidism, and systemic lupus erythematosus (SLE) are limited. The thyroid and parathyroid glands may be extra sensitive to irradiation damage in an underlying autoimmune condition. A 34-year-old black woman presented with tetanic-like cramps, easy skin bruising, fatigue, weight gain, nocturia and back pain. She was previously diagnosed with GD in 2001 and underwent radioiodine therapy (RAI) in 9/01 using 6 mCi. PostRAI (November 2001) she developed hypocalcemia and hypothyroidism (2/02). In 2007, SLE was diagnosed. In October 2009, s-calcium and PTH were still low at 7.1 mg/dl and 9 pg/mL, respectively, although the patient denied symptoms on vitamin D and calcium supplementation. To identify possible autoimmune damage of the parathyroids, we evaluated the presence of activating antibodies to the CaSR and also analyzed the DNA sequence of all 6 translated exons and flanking intronic sequences of her CaSR gene for a functionally significant CaSR mutation but neither was positive. The initial autoimmune damage to her thyroid and possibly parathyroid glands followed by irradiation of them seems to have contributed to her developing both hypoparathyroidism (11/01) and hypothyroidism (2002). The patient could potentially have had parathyroid autoantibodies in 2001 that disappeared by 2009 when she was tested for them. We consider that the multiple autoimmune conditions developed over the past decade of her life with the concurrent irradiation contributing to her brittle hypoparathyroidism. Select patients with GD and perhaps parathyroid autoantibodies with a slowly developing destructive impact on the parathyroid glands may then develop overt hyoparathyroidism with rather low dose RAI ablation. This patient adds to the evolving spectrum of polyglandular syndrome variants.

Hypocalcemia following treatment with radioiodine in a child with Graves' disease

BACKGROUND

Hypocalcemia is a rarely recognized complication of (131)I therapy that has been previously reported in only one child with Graves' disease treated with radioiodine (RAI). Here we report a second child with this occurrence.

PATIENT FINDINGS

A 12-year-old African American girl with hyperthyroidism due to Graves' disease and moderate persistent asthma, requiring oral prednisone, was treated with 11.1 mCi of RAI. While normocalcemic initially, the patient developed symptomatic hypocalcemia (6.6 mg/dL), within 3 months postablation. Concomitant findings included hyperphosphatemia, an inappropriately normal parathyroid hormone (PTH) level, vitamin D deficiency, and normal axial bone mineral density. After 2 weeks of treatment with calcium and calcitriol the symptoms of hypocalcemia resolved, and the calcium level returned to normal. PTH levels remained within the reference range throughout.

SUMMARY

In this child with Graves' disease, who was normocalcemic on presentation, RAI treatment was followed by compromised function of the parathyroid glands which was sufficient to produce symptomatic hypocalcemia. It is noteworthy and likely pertinent that the patient had a background of vitamin D deficiency and was receiving prednisone for asthma.

CONCLUSION

Patients scheduled to receive (131)I should be evaluated for risk factors for hypocalcemia in order to minimize the likelihood of this potentially serious complication.

The benefits and risks of I-131 therapy in patients with well-differentiated thyroid cancer

BACKGROUND

I-131 has been used in the therapy of well-differentiated thyroid cancer for over 50 years. Although the benefits and risks of I-131 remain issues of controversy and research, our understanding of them continues to improve. This review presents an overview of the benefits of I-131 therapy for ablation, adjuvant treatment, and treatment of locoregional and/or metastasis of well-differentiated thyroid cancer and considers the risks of complications of I-131 therapy.

SUMMARY

The benefits of I-131 remnant ablation include: [1] facilitating the interpretation of subsequent serum thyroglobulin levels, [2] increasing the sensitivity of detection of locoregional and/or metastatic disease on subsequent follow-up radioactive iodine whole-body scans, [3] maximizing the therapeutic effect of subsequent treatments, and [4] allowing a postablation scan to help identify additional sites of disease that were not identified on the preablation scan or when a preablation scan was not performed. The potential benefits of I-131 adjuvant treatment include decreasing recurrence and disease-specific mortality for unknown microscopic, locoregional, and/or distant metastatic disease. The potential benefits of I-131 treatment of known locoregional and/or distant metastases are [1] decreasing recurrence, and [2] decreasing disease-specific mortality and/or palliation. The more significant risks and side effects involve organ systems including eye/nasolacrimal, salivary, pulmonary, gastrointestinal, hematopoietic, and gonads as well as secondary primary malignancies.

CONCLUSIONS

Although there are never-ending controversies regarding I-131 therapy in well-differentiated thyroid cancer, the benefits and risks are becoming better understood. This in turn helps the treating physician and patient in making decisions regarding therapy.