Parathyroid allotransplantation for severe post-surgical hypoparathyroidism: a Brazilian experience

Abstract

This study presents the cases of two women who developed severe permanent hypoparathyroidism after neck surgery for papillary thyroid cancer and underwent parathyroid allotransplantation. Despite taking high doses of calcium and calcitriol supplements, the patients experienced persistent hypocalcemic symptoms. Fresh parathyroid tissue was removed and prepared from two patients with hyperparathyroidism secondary to end-stage kidney disease and was implanted in the non-dominant forearm of the recipients. Donors and recipients were ABO-compatible, and immunological screening was performed only in Case 2 (HLA typing, panel reactive antibody, and crossmatch tests). A short-term immunosuppressive regimen was adopted, consisting of 3 days of methylprednisolone followed by 7 days of prednisone. In Case 1, oral supplementation decreased to half of the initial dose 1 month after transplantation and to one-fifth at the end of a 12-month follow-up period. In Case 2, intravenous calcium was discontinued 1-week post-transplantation, with no need for its use during the 12-month follow-up period. Serum parathyroid hormone levels did not increase and remained undetectable in both cases. In contrast, serum calcium levels increased significantly, and both patients experienced relief from hypocalcemic symptoms. Parathyroid allotransplantation can be an effective and safe treatment for PH and should be considered in severe cases. Nevertheless, formal recommendations depend on additional studies and validated protocols.

Introduction

Hypoparathyroidism is a rare disease characterized by hypocalcemia and undetectable or inappropriately low levels of parathyroid hormone (PTH). Approximately 75% of cases are commonly caused by anterior neck surgery. Transient postsurgical permanent hypoparathyroidism (PH) is more common and refers to a condition where the PH lasts for less than 6 months. Conversely, if the condition persists for over 6 months, it is termed chronic or permanent. Long-term disease is associated with multiple morbidities such as fatigue, muscle cramps, paresthesia, laryngospasm, seizures, intracerebral calcifications, depression, cognitive dysfunction, and renal stones/nephrocalcinosis (Clarke et al. 2016; Bilezikian 2020).

Conventional treatment for PH comprises high-dose calcium and active vitamin D (calcitriol or an analog). However, this approach does not correct the baseline pathophysiological disturbance caused by a deficiency in PTH secretion. Once the phosphaturic effect of PTH is compromised, hyperphosphatemia may be aggravated by vitamin D metabolites. Hypercalciuria can also occur because of excessive calcium replacement. These disorders increase the risk of developing or worsening renal calcifications (Gafni and Collins 2019).

Recombinant human PTH (rhPTH) is a good option in severe cases (Clarke et al. 2017; Cusano et al. 2015; Palermo et al. 2018; Rubin et al. 2016; Tay et al. 2019; Winer et al. 2003; Khan et al. 2022) but is not available for most patients because of its high cost. Parathyroid allotransplantation (Pt-a) has been increasingly reported as an alternative treatment option for difficult-to-manage PH.

This study presents two cases of Pt-a from living donors as a treatment for severe uncontrolled PH. To the best of our knowledge, this is the first procedure performed on Brazilian patients.

Methods

Pre-operative evaluation

This study was approved by the local human ethics committee, and written informed consent was obtained from all patients. Standardized local serological screening for kidney transplants, including tests for HIV, hepatitis B and C, cytomegalovirus, Epstein-Barr virus, toxoplasmosis, Chagas disease, and venereal disease was performed in all patients (donors and recipients). Chemiluminescent Microparticle Immunoassay (CMIA) method was used for serological analyses, except for venereal disease (flocculation). Additional serological screening for HTLV (Human T-cell lymphotropic virus) was performed on donors (CMIA method). Recipients and donors had their ABO blood group determined.

Only case 2 underwent immunological assessment. The Panel reactive antibody (PRA) test was performed using One-Lambda Luminex via the flow cytometry method. Class I and II HLA antibodies were screened using a Mixed Kit. Positive samples were additionally tested for the specificity of antibodies against HLA-A, -B, -DR, and-DQ via sequence-specific oligonucleotide-primed (SSO) PCR method using a Single Antigen Kit. Fluorescence intensity was determined using a Luminex3D analyzer, and the data were analyzed using LABScan 3D software. Recipients were considered anti-HLA antibody positive when they had HLA antibodies with a median fluorescence intensity (MFI) > 1500. Furthermore, complement-dependent cytotoxicity crossmatch (CDC-XM)-auto-CDC-XM between recipients and donors was carried out.

Case 1

A 36-year-old female underwent neck surgery for papillary thyroid carcinoma in 2016. She rapidly developed severe hypoparathyroidism with cramps, paresthesia, tetany, and fatigue. She needed emergency care several times because of hypocalcemic symptoms. Therefore, calcium carbonate and calcitriol tablets were prescribed as standard treatment for permanent hypoparathyroidism. However, the patient reported abdominal pain and nausea, relieved partially after changing calcium carbonate to calcium citrate. Nevertheless, high doses of oral calcium citrate (15 tablets/day – equivalent to 3 g of elemental calcium) and three tablets/day of calcitriol (0.75 µg/day) were needed for disease control. Hydrochlorothiazide (25 mg/day) was administered to reduce the hypercalciuria. Subsequently, serum calcium levels ranged from 6.0 to 8.0 mg/dL, and PTH levels remained undetectable. The patient continued to experience hypocalcemic symptoms, which significantly affected her quality of life. She often could not engage in physical activity or go to work due to cramps, fatigue, and paresthesias. In addition, she frequently felt anxious. Her donor was a 47-year-old male diagnosed with severe hyperparathyroidism due to dialytic end-stage renal disease (undetermined etiology). His preoperative serum intact PTH levels were 1555 pg/mL. A standard parathyroid allotransplantation protocol was applied. The graft implant was done in the non-dominant forearm. Immunosuppression consisted of 10 days of corticosteroids. Bone biochemistry tests evaluated graft function and calcium and calcitriol management requirements. The patient was followed up for 12 months.

Case 2

A 40-year-old female had severe hypoparathyroidism after total thyroidectomy for papillary thyroid cancer treatment in 2008. She reported hypocalcemic symptoms immediately after surgery, including muscle cramps, paresthesia, and intense fatigue, which persisted even after hospital discharge. Similarly to Case 1, the patient developed severe gastrointestinal intolerance to calcium carbonate tablets, which were replaced with calcium citrate. The maximum tolerated dose of calcium citrate tablets was 8 units/day (3.2 g/day of elemental calcium) associated with four tablets/day of calcitriol (1.0 µg/day). However, the serum calcium levels remained low (6.0–7.0 mg/dL), and the patient continued to experience episodes of symptomatic hypocalcemia. Serum PTH levels ranged from 7.0 to 15 pg/mL. Therefore, she often visited the emergency department for intravenous calcium administration to improve serum calcium levels and relieve hypocalcemic symptoms. As she became dependent on intravenous calcium, she was scheduled for home calcium gluconate injections three times a week. Oral supplementation was stabilized at four tablets/day of calcium citrate (1.6 g of elemental calcium) and 1.0 µg/day of calcitriol. Even with the addition of intravenous calcium to her routine, the patient continued to experience hypocalcemic symptoms, which significantly worsened her quality of life. Her work was greatly affected, and she often felt fatigued. She was unable to leave home for extended periods due to the frequent need for intravenous calcium injections. Additionally, in 2017, bariatric surgery was performed to treat obesity. There were concerns about worsening serum calcium control due to intestinal calcium malabsorption. Nonetheless, there were no significant changes in the clinical state, and the need for calcium and calcitriol supplementation remained the same. Her donor was a 35-year-old female with hyperparathyroidism because of hypertensive nephropathy. Her preoperative serum intact PTH level was 2209 pg/mL. The same parathyroid allotransplantation protocol described above was applied to this case. Nevertheless, an immunological assessment was performed only in this case. As no validated protocols recommend it, we decided to verify if this approach could improve graft function. The follow-up duration was 12 months.

Transplantation

The following steps were applied in both cases: (1) Parathyroid excision was performed from the donor (three and a half parathyroid glands) via anterior cervical incision. (2) Approximately 1 cm³ of parathyroid tissue was reserved for grafting. To ensure optimal viability, the tissue was carefully dissected to remove fat tissue, fibrotic capsules, and blood vessels. It was then fragmented into small pieces for further use. (3) An incision of approximately 3 cm was performed on the recipient’s non-dominant forearm. Local anesthesia (xylocaine 1%) was administered to minimize discomfort. (4) Freshly prepared parathyroid tissue was immediately implanted under the fascia of the brachioradialis muscle. (5) The recipient remained under observation in the hospital for approximately 1 h.

Immunosuppression

Immunosuppression was performed as described previously (Yucesan et al. 2017). Intravenous methylprednisolone was administered for three consecutive days at 250, 125, and 60 mg 1 h before grafting, 24 h, and 48 h after implant, respectively. Thereafter, oral prednisone (5 mg/day) was administered for 7 days, which resulted in immunosuppression for 10 days.

Antiparasitic treatment was administered to two recipients owing to corticosteroid exposure; albendazole (400 mg/day) was administered for 5 days, and secnidazole (1 g) as a single dose.

Graft function and follow-up

Serum levels of PTH, calcium, phosphorus, and albumin were measured on the first-day post-transplantation and weekly in the first month after the procedure. Blood samples were collected at least monthly. Additional assessments, including worsening symptoms or withdrawal of calcium/calcitriol tablets, were performed as often as necessary. Calcium and vitamin D supplementation were managed according to hypocalcemic symptoms and PTH/calcium levels.

Calcium levels were corrected by albumin according to the following formula: corrected calcium (mg/dL) = serum calcium + 0.8 (4.0—serum albumin).

Results

The serological screening was negative for all patients. Recipients and donors were ABO compatible.

Case 1

The procedure was performed as scheduled, and no post-surgical complications such as bleeding, infection, or significant local pain were observed. Figure 1 shows the parathyroid tissue preparation and implantation in the recipient.

Fig. 1.

Case 1: fresh allotransplantation of parathyroid glands. a Isolation of parathyroid glands after washing and removing surrounding tissues. b Fragmentation of the parathyroid tissue. c Allograft implantation in the recipient’s forearm

Calcium supplementation was reduced by half 1 month after surgery, and calcitriol was discontinued after 6 months. The patient took only four citrate calcium tablets (approximately 800 mg of elemental calcium) at the end of the 12 month follow-up period. This indicates a reduction of approximately one-fifth of the initial supplementation dose. Although calcemia theoretically allows for further reduction of calcium supplementation, the patient reported significantly worsening symptoms, mainly fatigue and numbness. Hypocalcemic symptoms were generally markedly reduced, and her quality of life improved considerably. Serum PTH levels did not increase as expected but were detectable at 8 and 12 months after implantation. In contrast, the calcium levels remained stable throughout the follow-up period (Table 1).

Table 1.

Case 1: post-transplant serum PTH, calcium, and phosphorus levels

	Weeks after transplantation
	01	03	04	14	27	37	40	52
PTH	Un	Un	Un	Un	Un	7,0	Un	3,1
Ca	12.1	10.2	9.6	8.0	8.3	8.5	8.1	8.8
P	5.6	3.8	4.6	4.5	5.3	5.0	4.7	5.4

PTH parathyroid hormone, Ca calcium, P phosphorus, Un undetectable

Reference values: PTH: 11–67 pg/mL; Ca: 8.6–10.2 mg/dL; P: 2.5–5.6 mg/dL

Case 2

Immunological evaluation revealed negative results for PRA screening and crossmatch tests. HLA typing indicated matches between two HLA alleles at different loci (HLA-B and HLA-DQ). Table 2 shows the HLA matching/mismatching between donor and recipient.

Table 2.

Case 2: donor and recipient HLA match/ mismatch

	HLA typing
	Class I		Class II
	HLA-A	HLA-B	HLA-DRB1	HLA-DQB1
Donor	A*03 A*11	B*08 B*61	DRB1*17 DRB1*15	DQB1*02 DQB1*06
Recipient	A*01 A*29	B*57 B*61	DRB1*07 DRB1*07	DQB1*02 DQB1*09

HLA human leucocyte antigens

Implantation was planned, and the patient was discharged without complications. She complained of headaches for a few hours after the procedure, which lasted for 24 h. Her blood pressure was normal, and she was instructed to take the usual analgesics. Mild local pain relieved by the same analgesics has also been reported. Ecchymosis was observed around the implant site 48 h after surgery, which was monitored by the same surgeon. Spontaneous resolution was observed after 15 d. No fever or signs of local or systemic infection were observed (Fig. 2).

Fig. 2.

Case 2: Fresh allotransplantation of parathyroid glands. a Isolation of parathyroid glands after washing and removing surrounding tissues. b Fragmentation of the parathyroid tissue. c Allograft implantation in the recipient’s forearm. d Ecchymosis 1 week after implantation. e Cicatrization 3 months after implantation

The patient reported symptom relief in the first week after transplantation and no longer required intravenous calcium injections. Serum PTH levels were detectable but did not increase to normal values. In contrast, serum calcium levels increased, although there was a mild decrease in the last two assessments (Table 3). Twelve months after transplantation, her calcium and calcitriol supplementation were six tablets/day of calcium citrate (2.4 g/day of elemental calcium) and only one tablet/day of calcitriol (0.25 µg/day). No intravenous calcium administration was required during the follow-up. She considered her quality of life to have significantly improved.

Table 3.

Case 2: Serum PTH, calcium, and phosphorus levels

	Weeks after transplant
	01	02	05	12	26	40	49
PTH	3.7	4.19	6.8	In	In	8.2	6
Ca	8.0	8.0	8.9	8.0	7.6	7.4	8.4
P	4.8	4.6	4.5	4.8	4.9	4.8	4.7

PTH parathyroid hormone, Ca calcium, P phosphorus, Un undetectable

Reference values: PTH: 11–67 pg/mL; Ca: 8.6–10.2 mg/dL; P: 2.5–5.6 mg/dL

Discussion

PH is typically treated with calcium and vitamin D supplements. Some patients achieve optimal disease control with simple regimens, others require high supplementation doses, and a subgroup of patients have refractory diseases. Furthermore, individual characteristics, such as gastrointestinal intolerance to therapy, can significantly affect treatment adherence. Our two cases can be classified as hard-to-control diseases aggravated by severe gastrointestinal complaints.

rhPTH molecules have been reported as an interesting treatment option for refractory PH because they restore the physiology of PTH. Two injectable subcutaneous formulations are available: rhPTH 1–84 (whole molecule) and rhPTH 1–34 (active amino-terminal portion). They are usually administered intermittently (once for rhPTH 1–84 and twice daily for rhPTH 1–34). TransCon PTH is a long-acting prodrug derived from PTH-34. These compounds have been proven safe and effective in patients with hypoparathyroidism by suspension or significant reduction in calcium and vitamin D replacement (Clarke et al. 2017; Palermo et al. 2018; Rubin et al. 2016; Tay et al. 2019; Winer et al. 2003; Khan et al. 2022). Improvements in quality of life have also been reported (Palermo et al. 2018; Tabacco et al. 2019). The Food and Drug Administration (FDA) approved rhPTH 1–84 use for PH in 2015 and the European Medicines Agency (EMA) in 2017. rhPTH 1–34 has been approved for osteoporosis treatment for 2 years but has yet to be approved for PH. Furthermore, there is concern about using these molecules because of the risk of osteosarcoma in rats (Vahle et al. 2002; Jolette et al. 2006). However, this phenomenon has yet to be described in humans.

Because rhPTH is not available for most patients with PH because of its high cost, Pt-a has been reported as an alternative treatment option for refractory PH. The first successful Pt-a was published in 1973 (Groth et al. 1973). The recipient developed severe PH after renal transplantation. He had previously undergone subtotal parathyroidectomy for secondary hyperparathyroidism. The grafts survived for approximately 21 months.

Although Pt-a is not a new approach to treating PH, some obstacles have been identified. For instance, immunosuppression is a safety concern. Some studies have reported Pt-a in patients who were already immunosuppressed (kidney transplant) or in whom simultaneous parathyroid-kidney transplantation was intended (Groth et al. 1973; Flechner et al. 2010; Chapelle et al. 2009; Garcia-Roca et al. 2016; Torregrosa et al. 2005; Vallant et al. 2022). However, Agha et al. published the first case of living-related Pt-a in a non-transplant patient with post-surgical PH (the donor was her healthy brother) (Agha et al. 2016). Immunosuppression was induced using a kidney transplantation regimen comprising prednisolone, basiliximab, and tacrolimus. No side effects related to the immunosuppressive drugs were observed. Serum PTH and calcium levels normalized, and calcium/calcitriol replacement was stopped after three years of follow-up. Other successful cases of Pt-a have been reported in non-transplant patients with unrelated donors (Yucesan et al. 2017; Hermosillo-Sandoval et al. 2015; Aysan et al. 2016a, b; Aysan et al. 2019; Yucesan et al. 2019a, b; Goncu et al. 2021).

Several techniques have been developed to minimize graft rejection. Cell encapsulation consists of a semi-permeable membrane that protects the graft from mechanical stress and the host immune system while simultaneously allowing nutrition and oxygenation of the parathyroid tissue. This procedure enabled the development of Pt-a without immunosuppression (Cabané et al. 2009; Toledo et al. 2017; Khryshchanovich et al. 2016; Yucesan et al. 2019a, b). Cultured and cryopreserved parathyroid cells decrease the expression of major histocompatibility complex molecules in parathyroid cells and reduce the probability of graft rejection (Flechner et al. 2010; Barczyński et al. 2017). Immunological assessment via HLA typing, PRA, crossmatch tests, and donor-specific antigen (DSA) monitoring have been reported as additional tools to improve graft survival (Yucesan et al. 2019a, b; Goncu et al. 2021).

Nevertheless, validated recommendations for this approach for Pt-a still need to be included. Yucesan et al. reported that four patients with post-surgical PH underwent Pt-a from the same donor (Yucesan et al. 2019a, b). Although one recipient tested positive for both PRA (HLA class II) and DSA in the fourth year, she did not show any signs of rejection. PTH and calcium levels remained normal, and medications before transplantation were not restarted. The other recipient remained negative for PRA and DSA without graft rejection. Therefore, the authors concluded that immunological assessments should be performed more formally for Pt-a.

Moreover, studies have diverged in methodology about immunosuppressive drugs and their time of use (ranging from 3 days to 4 years), implant site (brachioradialis muscle, deltoid muscle, omentum), additional resources to minimize the risk of rejection (HLA typing and crossmatch tests, cryopreserved and cultured parathyroid cells), and follow-up period.

Our two cases of Pt-a were performed using fresh parathyroid tissue. Preparing fresh graft tissue is easy, and the implantation can be performed immediately. Encapsulated and cultured cells are costly and require additional equipment and well-trained staff (Aysan et al. 2016a, b). Although Case 2 developed local ecchymosis, it was spontaneously absorbed. Since no serious adverse effects were observed, the procedure was considered safe.

Intriguingly, the evolution patterns of serum PTH levels were similar in both cases. As they remained low, optimal graft function could not be documented using this parameter. In contrast, the serum calcium levels increased and remained stable during follow-up. Furthermore, the oral calcium and calcitriol supplementation decreased significantly. In Case 1, it remained at approximately one-fifth of the initial dose. Although this reduction was not as pronounced in Case 2, intravenous calcium administration was no longer required. Hypocalcemic symptoms were markedly reduced in both cases. From this point of view, the grafted parathyroid tissue remains functional.

Goncu et al. (2021) reported similar results. Pt-a using cryopreserved and cultured parathyroid cells was performed in a patient with PH after total thyroidectomy. The donor had a chronic kidney disease. The recipient and donor were HLA-A-matched. Immunosuppression comprised 3 days of intravenous methylprednisolone. The graft was implanted laparoscopically on the omental surface. Serum PTH levels did not increase, but serum calcium levels did, and calcium/calcitriol supplementation was reduced by one-third.

Conclusion

Pt-a can be considered a safe and effective alternative treatment for PH, especially in patients whose PH is refractory to calcium and calcitriol supplementation. Implantation of fresh parathyroid tissue into the forearm is a well-known technique that is easy to perform. Furthermore, Pt-a is a less expensive option, considering the high cost of rhPTH and its inviability for most patients. Notably, this is the first Brazilian experience with Pt-a. Validated protocols are lacking, and further studies should be conducted to obtain Pt-a as a formal therapy for PH.

Author contributions

All authors contributed to the study’s conception. All authors read and approved the final manuscript.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article.

Declarations

Conflict of interest

The authors have no relevant financial or non-financial interests to disclose.

Ethical approval

The study was approved by the research ethics committee of Walter Cantidio Hospital (No. 3.857.828) on February 27, 2020.

Consent to participate

Informed consent was obtained from all individual participants included in the study.

Consent to publish

The authors affirm that the participants provided informed consent to publish the images in Figs. 1 and 2.