Parathyroid Allotransplant for Severe Refractory Hypoparathyroidism

A protocol for deceased donor parathyroid transplantation was developed with the University Health Network Ajmera Transplant Centre in Toronto, relevant stakeholders, and presented to the innovation committee and REB for approval. Health Canada approval was obtained under the scope of existing cell tissue and organ regulations within the provincial organ procurement agency.

This is a pilot, prospective case-series. It includes a cohort of patients with hypoparathyroidism who will undergo parathyroid transplantation from a neurologically deceased donor. There is no control group in this study.

Patients with permanent refractory hypoparathyroidism after total thyroidectomy will be entered in this study to undergo parathyroid transplantation from a neurologically deceased donor. Inclusion criteria are patients who have had a prior total thyroidectomy with both biochemical hypoparathyroidism and symptomatic hypocalcemia (numbness, tingling, or other neurologic symptoms) requiring daily high dose calcium (greater than 2000 mg per day), vitamin D (greater than 2 mcg of calcitriol per day) supplementation and/or intermittent IV calcium infusion. Patients for inclusion must have failed this medical management after at least 1 year of treatment and meet standard criteria for receiving organ transplant.

All patients will have at least one pre-operative clinic visit with the endocrine surgery, endocrinology, and transplant team for comprehensive assessment. Baseline blood work will be conducted at this pre-operative visit, as outlined in the study protocol. The patient will also be evaluated by psychiatry and complete any necessary age appropriate comprehensive cancer screening as per standard transplantation protocol. Completeness of pre-transplant vaccinations (pneumococcus, HBV, influenza, Tdap, HAV) will be reviewed and arranged in co-ordination with patients' primary care provider as necessary. If based on pre-transplant work up a participant is deemed to meet exclusion criteria and not be suitable for transplant this will be discussed with the participant, and they will be withdrawn from the study. Participants will be informed of the need to fulfill the previously listed standard transplant criteria during the informed consent process.

Once a potential donor becomes available, the transplant team will decide whether the donor is a match for a study participant. A rigorous protocol for donor selection and transplantation was developed. Donor criteria aimed at minimizing infectious and immunological risks (HLA matching). A history of hyperparathyroidism (primary, secondary or tertiary) will also be screened for in the donor as the presence of hyperparathyroidism would be an exclusion criteria to procure their parathyroid glands for this study. If the donor is a match for a study participant, the participant will be contacted and timing of retrieval and patient arrival at TGH will be coordinated. The procurement team will then, with appropriate timing, procure all parathyroid tissue using standard surgical techniques and the tissue will be kept in organ preservation solution in a sterile specimen cup with a cold ischemic time of less than 2 hours.