Long term parathyroid function following total parathyroidectomy with autotransplantation in adult patients with MEN2A

The role of prophylactic parathyroidectomy during thyroidectomy for MTC in patients with MEN2A syndrome

AIM

To define the role of prophylactic parathyroidectomy in the surgical treatment of medullary thyroid carcinoma (MTC) in multiple endocrine neoplasia type IIa (MEN2A) syndrome through a literature review.

Primary Hyperparathyroidism in Multiple Endocrine Neoplasia Type 2A in Denmark 1930–2021: A Nationwide Population-Based Retrospective Study

Studies of primary hyperparathyroidism (PHPT) in multiple endocrine neoplasia type 2A (MEN 2A) shows divergence in frequency, disease definition, reporting of clinical characteristics and traces of selection bias. This is a nationwide population-based retrospective study of PHPT in MEN 2A, suggesting a representative frequency, with complete reporting and a strict PHPT definition. The Danish MEN 2A cohort 1930-2021 was used. Of 204 MEN 2A cases, 16 had PHPT, resulting in a frequency of 8% (CI, 5-12). Age-related penetrance at 50 years was 8% (CI, 4-15). PHPT was seen in the American Thyroid Association moderate (ATA-MOD) and high (ATA-H) risk groups in 62% and 38% of carriers, respectively. Median age at PHPT diagnosis was 45 years (range, 21-79). A total of 75% were asymptomatic and 25% were symptomatic. Thirteen underwent parathyroid surgery, resulting in a cure of 69%, persistence in 8% and recurrence in 23%. In this first study with a clear PHPT definition and no selection bias, we found a lower frequency of PHPT and age-related penetrance, but a higher age at PHPT diagnosis than often cited. This might be affected by the Danish RET p.Cys611Tyr founder effect. Our study corroborates that PHPT in MEN 2A is often mild, asymptomatic and is associated with both ATA-MOD and ATA-H variants. Likelihood of cure is high, but recurrence is not infrequent and can occur decades after surgery.

Looking beyond the thyroid: advances in the understanding of pheochromocytoma and hyperparathyroidism phenotypes in MEN2 and of non-MEN2 familial forms

Over the last years, the knowledge of MEN2 and non-MEN2 familial forms of pheochromocytoma (PHEO) has increased. In MEN2, PHEO is the second most frequent disease: the penetrance and age at diagnosis depend on the mutation of RET Given the prevalence of bilateral PHEO (50% by age 50), adrenal sparing surgery, aimed at sparing a part of the adrenal cortex to avoid adrenal insufficiency, should be systematically considered in patients with bilateral PHEO. Non-MEN2 familial forms of PHEO now include more than 20 genes: however, only small phenotypic series have been reported, suggesting that phenotypic features of isolated hereditary PHEO must be better explored, and follow-up series are needed to better understand the outcome of patients carrying mutations of these genes. The first part of this review will mainly focus on these points. In the second part, a focus will be given on MEN2 and non-MEN2 familial forms of hyperparathyroidism (HPTH). Again, the management of MEN2 HPTH should be aimed at curing the disease while preserving an optimal quality of life by a tailored parathyroidectomy. The phenotypes and outcome of MEN1-, MEN4- and HRPT2-related HPTH are briefly described, with a focus on the most recent literature data and is compared with familial hypocalciuric hypercalcemia.

Advances in risk-oriented surgery for multiple endocrine neoplasia type 2

Genetic association studies hinge on definite clinical case definitions of the disease of interest. This is why more penetrant mutations were overrepresented in early multiple endocrine neoplasia type 2 (MEN2) studies, whereas less penetrant mutations went underrepresented. Enrichment of genetic association studies with advanced disease may produce a flawed understanding of disease evolution, precipitating far-reaching surgical strategies like bilateral total adrenalectomy and 4-gland parathyroidectomy in MEN2. The insight into the natural course of the disease gleaned over the past 25 years caused a paradigm shift in MEN2: from the removal of target organs at the expense of greater operative morbidity to close biochemical surveillance and targeted resection of adrenal tumors and hyperplastic parathyroid glands. The lead time provided by early identification of asymptomatic MEN2 carriers under biochemical surveillance delimits a 'window of opportunity', within which (i) pre-emptive total thyroidectomy alone is adequate, circumventing morbidity attendant to central node dissection; (ii) subtotal 'tissue-sparing' adrenalectomy is sufficient, trading the risk of steroid dependency for the risk of a second pheochromocytoma in the adrenal remnant and (iii) parathyroidectomy is limited to enlarged glands, trading the risk of postoperative hypoparathyroidism for the risk of leaving behind hyperactive parathyroid glands. Future research should delineate further the mutation-specific, age-dependent penetrance of pheochromocytoma and primary hyperparathyroidism to refine the risk-oriented approach to MEN2. The sweeping changes in the management of MEN2 since the new millenium hold the hope that death and major morbidity from this uncommon disease can be eliminated in our lifetime.

Recurrent hyperparathyroidism due to proliferation of autotransplanted parathyroid tissue in a multiple endocrine neoplasia type 2A patient

About 20%–30% of all cases of multiple endocrine neoplasia type 2A (MEN 2A) is accompanied by primary hyperparathyroidism. These patients undergo parathyroidectomy and, if needed, autotransplantation. In rare cases, autotransplanted parathyroid tissues can cause hypoparathyroidism due to failure of transplantation or hyperparathyroidism due to proliferation of the transplanted tissue. A 68-year-old female with MEN 2A underwent left adrenalectomy for pheochromocytoma 15 years prior to presentation and total thyroidectomy, central and right lateral neck lymph node dissection, and subtotal parathyroidectomy with autotransplantation for medullary thyroid cancer and primary hyperparathyroidism 6 years previous. Recently, a doubtful parathyroid adenoma was detected in the left sternocleidomastoid muscle on ultrasonography and on an additional sestamibi scan. The mass was excised and histologically confirmed as parathyroid adenoma. This is a very rare case, and it suggests that long-term regular monitoring of serum calcium and intact parathyroid hormone levels is necessary after parathyroid autotransplantation.

Primary Hyperparathyroidism in MEN2 Syndromes

One of the components of trethe classical form of MEN2 syndromes is primary hyperparathyroidism (PHP). It occurs in 20-30% of the typical MEN2A syndrome. The prevalence is more rare in gene carriers as these frequently have familial MTC only. PHP is diagnosed more frequently in association with the exon 11, codon 634 mutation of the ret gene-so there is phenotype/genotype correlation. The clinical manifestations of PHP in MEN2 are usually mild and the peak age of diagnosis after the 3rd decade. The treatment is surgical excision of the enlarged gland(s). Although there can be multigland disease in the parathyroids, it is frequently the case that both hyperplasia and adenoma may coexist, or even a single adenoma may be found during the investigation and finally during the operation. Patients with MEN2 syndromes should be screened for PHP with serum calcium measurements. The intensity of the screening should be higher in those carrying the ret mutations most frequently associated with this manifestation.

Autotransplantation of Inferior Parathyroid glands during central neck dissection for papillary thyroid carcinoma: a retrospective cohort study

INTRODUCTION

The management of inferior parathyroid glands during central neck dissection (CND) for papillary thyroid carcinoma (PTC) remains controversial. Most surgeons preserve inferior parathyroid glands in situ. Autotransplantation is not routinely performed unless devascularization or inadvertent parathyroidectomy occurs. This retrospective study aimed to compare the incidence of postoperative hypoparathyroidism and central neck lymph node (CNLN) recurrence in patients with PTC who underwent inferior parathyroid glands autotransplantation vs preservation in situ.

METHODS

This is a retrospective study which was conducted in a tertiary referral hospital. A total of 477 patients with PTC (pN1) who underwent total thyroidectomy (TT) and bilateral CND with/without lateral neck dissection were included. Patients' demographical characteristics, tumor stage, incidence of hypoparathyroidism, CNLN recurrence and the number of resected CNLN were analyzed.

RESULTS

Three hundred and twenty-one patients underwent inferior parathyroid glands autotransplantation (autotransplantation group). Inferior parathyroid glands were preserved in situ among 156 patients (preservation group). Permanent hypoparathyroidism rate was 0.9% (3/321) versus 3.8% (6/156) respectively (p = 0.028). Mean numbers of resected CNLN were 15 ± 3 (6-23) (autotransplantation group) versus 11 ± 3 (7-21) (preservation group) (p < 0.001). CNLN recurrence rate was 0.3% (1/321) versus 3.8% (6/156) respectively (p = 0.003).

CONCLUSION

Inferior parathyroid glands autotransplantation during CND of PTC (pN1) might reduce permanent hypoparathyroidism and CNLN recurrence. Further study enrolling more patients with long-term follow-up is needed to support this conclusion.

Multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma: an update

CONTEXT

Over the last decade, our knowledge of the multiple endocrine neoplasia (MEN) type 2 syndromes MEN2A and MEN2B and familial medullary thyroid carcinoma (FMTC) has expanded greatly. In this manuscript, we summarize how recent discoveries have enhanced our understanding of the molecular basis of these diseases and led to improvements in the diagnosis and management of affected patients.

EVIDENCE ACQUISITION

We reviewed the English literature through PubMed from 2000 to the present, using the search terms medullary thyroid carcinoma, multiple endocrine neoplasia type 2, familial medullary thyroid carcinoma, RET proto-oncogene, and calcitonin.

EVIDENCE SYNTHESIS

Over 70 RET mutations are known to cause MEN2A, MEN2B, or FMTC, and recent findings from studies of large kindreds with these syndromes have clouded the relationship between genotype and phenotype, primarily because of the varied clinical presentation of different families with the same RET mutation. This clinical variability has also confounded decisions about the timing of prophylactic thyroidectomy for MTC, the dominant endocrinopathy associated with these syndromes. A distinct advance has been the demonstration through phase II and phase III clinical trials that molecular targeted therapeutics are effective in the treatment of patients with locally advanced or metastatic MTC.

CONCLUSIONS

The effective management of patients with MEN2A, MEN2A, and FMTC depends on an understanding of the variable behavior of disease expression in patients with a specific RET mutation. Information gained from molecular testing, biochemical analysis, and clinical evaluation is important in providing effective management of patients with either early or advanced-stage MTC.

Management of hyperparathyroidism (PHP) in MEN2 syndromes in Europe

Hyperparathyroidism occurs in 20-30% of MEN2A syndrome patients. It is usually associated with mild disease and is frequently asymptomatic, especially in younger age. There is genotype/phenotype association and PHP is usually associated with codon 634 mutations; however association with more “rare” mutations has also been reported. The pathology of the parathyroid glands includes hyperplasia, adenoma or a combination of the two. The optimal surgical management of this entity has not been defined yet.

Sleeping parathyroid tumor: rapid hyperfunction after removal of the dominant tumor

CONTEXT

Due to frequent multiplicity of tumors in multiple endocrine neoplasia type 1, it may be difficult to decide when to stop a parathyroid exploration. A fall of intraoperative serum PTH by a certain percentage during parathyroid surgery is often used as one criterion for ending the operation.

RESULTS

We report two patients with primary hyperparathyroidism due to multiple endocrine neoplasia type 1 who had their first parathyroidectomy at the National Institutes of Health. In both cases, two and a half glands were removed, an extensive search was done for an occult parathyroid tumor, and intraoperative PTH decreased markedly to the lower limits of normal, suggesting a successful operation. Despite this, both patients became hypercalcemic within 3 d after the operation and showed persistent primary hyperparathyroidism. Detailed findings suggest the following course: chronic hypercalcemia had caused near total suppression of PTH secretion by an undiscovered parathyroid tumor (sleeping parathyroid tumor). When the hypercalcemia decreased after surgery due to the removal of the dominant parathyroid tumor(s), the abnormal yet previously suppressed tumor rapidly began to oversecrete PTH and thus caused postoperative hypercalcemia.

CONCLUSIONS

Even a fall of the intraoperative PTH to the lower limits of the normal range cannot guarantee that removal of all parathyroid tumors has been complete in cases with multiple tumors. These findings likely reflect strikingly differing PTH secretory functions among distinct tumors in the same patient, with hypercalcemia at least from a dominant tumor suppressing PTH secretion by one or more other parathyroid tumors.