Parathyroid Allotransplant With a New Technique: A Prospective Clinical Trial

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

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.

Is parathyroid allotransplantation a viable option in the treatment of permanent hypoparathyroidism? A review of the literature

BACKGROUND

The standard clinical treatment for hypoparathyroidism, replacement of calcium and vitamin metabolites (calcitriol), has been used for decades; however, evidence points to its inefficiency in acting on the pathophysiology of the disease, which may precipitate or aggravate conditions already related to hypoparathyroidism. Therapies based on recombinant human parathyroid hormone have emerged in recent years but still have low availability due to their high cost. Parathyroid allotransplantation (Pt-a) has been reported as a strategy for treating more severe cases.

METHODS

This narrative review highlights relevant aspects of conventional permanent hypoparathyroidism treatment and provides a comprehensive and critical review of the reports of applications of Pt-a, especially those carried out in recent years. Particular focus is placed on the following key points: parathyroid immunogenicity, immunosuppression regimens (short-term or chronic), techniques to reduce the expression of immunogenic molecules, follow-up time, and reductions in calcium and vitamin D supplementation.

CONCLUSION

Pt-a has been considered a safe and relatively low-cost therapy and is believed to have the potential to cure the disease, in addition to treating symptoms. However, there is considerable heterogeneity in treatment protocols; therefore, more studies are required to improve the standardization of the procedure and thus improve the consistency of outcomes.

Hypoparathyroidism: State of the Art on Cell and Tissue Therapies

Hypoparathyroidism is an endocrine disorder characterized by low serum calcium levels, high serum phosphorus levels, and by inappropriate or absent secretion of the parathyroid hormone (PTH). The most common therapeutic strategy to treat this condition is hormone replacement therapy with calcium and vitamin D but, unfortunately, in the long term this treatment may not be sufficient to compensate for the loss of endocrine function. Glandular autotransplantation is considered the most effective technique in place of replacement therapy. Although it leads to excellent results in most cases, autotransplantation is not always possible. Allograft is a good way to treat patients who have not been able to undergo autograft, but this technique has limited success due to side effects related to tissue rejection. This therapy is supported by systemic immunosuppression, which leads to the onset of serious side effects in patients, with a risk of endocrine toxicity. Today, research on endocrine disorders is focused on discovering alternative graft therapies that can allow optimal results with the fewest possible side effects. In this review, we will make an update on the current state of the art about the cell and tissue therapy as treatment for hypoparathyroidism, to identify which type of therapeutic strategy could be valid for a future clinical use.

Patients' views about parathyroid transplantation for post-thyroidectomy hypoparathyroidism

BACKGROUND

Permanent hypoparathyroidism (hypoPT) represents the most common postoperative complication associated with total thyroidectomy. Current treatment relies on high-dose calcium and/or vitamin D supplementation, but often this is insufficient and some patients remain symptomatic. Parathyroid allotransplantation is a new therapeutic option described recently in the literature. This study aims to investigate the patients' acceptability of parathyroid transplantation as a potential new treatment for hypoPT.

METHOD

Online survey of members of HypoParaUK, a support group for individuals affected by hypoPT.

RESULTS

Responses were received from 252 hypoPT patients. Majority declared to experience severe symptoms despite regular medical treatment. On a severity scale of 0-5, symptoms that were most troublesome were fatigue (3.8), low sense of well-being (3.5), and numbness/tingling (2.9). On a scale of 0-10, on average, their current quality of life (QoL) was 5 ± 3 and they expected this would improve to 7 ± 2 with correction of their hypoPT. Forty-four percent of patients were extremely interested in a potential technique involving intramuscular injection of parathyroid cell suspension compared to just 14% who were interested in the more invasive procedure of implantation of a parathyroid allograft into the forearm. The main concerns expressed were related to the possible need for immunosuppressive therapy.

CONCLUSION

Patients with severe symptomatic hypoPT seem interested to consider participation in a clinical trial exploring the feasibility and success rate of parathyroid transplantation.