Predicting the successfulness of parathyroidectomy: new lessons from an old challenge

Correspondência para: Fellype Carvalho Barreto. Hospital de Clínicas da Universidade Federal do Paraná. Rua General Carneiro, 181. 12o andar. CEP: 80060-900. Curitiba Paraná Brazil. E-mail: fellype.barreto@ufpr. com O hiperparatireoidismo secundário (HPTS) é um dos principais distúrbios endócrinos da doença renal crônica (DRC). O HPTS está associado a anomalias ósseas e cardiovasculares, bem como a elevada mortalidade. Apesar dos progressos na terapia farmacológica, o HPTS ainda evolui em um número considerável de pacientes para autonomia, quando a paratireoidectomia se torna o único tratamento possível.1 No Brasil, cerca de 10% dos pacientes em terapia renal substitutiva apresentam HPTS grave, o que significa que em torno de onze mil indivíduos podem precisar de paratireoidectomia.2 Há três técnicas para tal cirurgia: paratireoidectomia subtotal; paratireoidectomia total; e paratireoidectomia total com autoimplante. Ainda não há consenso sobre qual abordagem é mais eficaz. Contudo, a paratireoidectomia total com autoimplante é atualmente o procedimento mais comumente realizado.3 A persistência e a recorrência de HPTS são importantes desvantagens da paratireoidectomia que cirurgiões e nefrologistas podem ter que enfrentar. Vários estudos avaliaram a utilidade de biomarcadores selecionados na predição de tais complicações. Em um estudo recente em que foi medido o PTH intraoperatório por ensaio imunométrico rápido, uma redução de pelo menos 80% nos níveis de PTH dez minutos após a cirurgia foi identificada como um bom preditor de sucesso da paratireoidectomia.4 O custo e a baixa disponibilidade do ensaio têm impossibilitado seu uso na prática clínica de rotina. A medição de Como predizer o sucesso da paratiroidectomia: novas lições de um velho desafio


Predicting the successfulness of parathyroidectomy: new lessons from an old challenge
Como predizer o sucesso da paratiroidectomia: novas lições de um velho desafio As so, using it to evaluate the efficacy of parathyroidectomy may be a reasonable strategy.
In this issue of the Brazilian Journal of Nephrology, Nascimento Junior et al. 5 evaluated, in a cohort of fiftyone end-stage renal disease patients submitted to total parathyroidectomy with autotransplantation, whether PTH measurement in the first days after surgery would be a helpful tool to predict the surgical success and, consequently, the risk of persistence and recurrence of the disease.
They observed that a decline of 95% of the PTH levels was associated with a high rate of sHPT resolution.Actually, neither persistence nor recurrence were detected in those patients who achieved that cut-off level of PTH after a follow-up up to sixty months.Conversely, reduction of PTH levels lower than 80% was associated with sHPT persistence even in those patients who developed postsurgical hypocalcemia, considered an indicative of hungry bone syndrome and an indirect marker of the success of the surgery.
The present study is of great relevance not only for surgeons, but also for nephrologist who are, in the majority of institutions, responsible for the follow up of theses patients.On one hand, from the surgeon perspective, sHPT persistence may be seen as a therapeutic failure, for which early surgical reintervention, before the development of tissue fibrosis, is desirable.On the other hand, from the nephrologist point of view, persistence does not necessarily mean that a new DOI: 10.5935/0101-2800.20170024surgery is required or that clinical treatment is not possible.Even when autonomous parathyroid glands are not completely removed, clinical and metabolic improvements occur, such as lower serum levels of calcium and phosphate.In this scenario, persistent sHPT may be pharmacological treated.
Other complication commonly seen after parathyroidectomy, that is post-surgical hypoparathyroidism (characterized by PTH levels persistently low), should be equally avoided.Patients with post-surgical hypoparathyroidism are more prone to low turnover bone disease, bone fractures and vascular calcification.Therefore, the evaluation of the success of parathyroidectomy should be based not only on the persistence/recurrence of sHPT, but also on the development of post-surgical hypoparathyroidism.Both complications should have been considered by the authors in order to determinate the best post-operative cut-off level of PTH.This would have strengthened their findings.One question that may be raised from the study is if adequate control of the persistent sHPT was achieved.This point deserve further investigation as it can help nephrologists to further understand how patients should be managed post-parathyroidectomy in the long term.
One take home message of the study that should be highlighted is: not achieving the proposed 95% reduction of PTH levels within the first days after parathyroidectomy should call the nephrologists attention for the possibility that early reintroduction of pharmacological therapy for sHPT may be required for precluding disease progression and necessity of a new surgical intervention.
sHPT is an old challenge for nephrologists.Multidisciplinary approach, including parathyroidectomy for the severe cases, is usually required to achieve adequate control of the disease.Clinical studies with interdisciplinary characteristics, such as the Nascimento Junior's study, must be stimulated.They have certainly more chance to gift medical community with new knowledge and strategies to improve the medical practice and, consequently, the patient care.