Genetics of Hyperparathyroidism, Including Parathyroid Cancer

Diagnosis and Management of Parathyroid Carcinoma

Parathyroid carcinoma (PC) is a rare malignancy, often characterized by the unregulated secretion of parathyroid hormone. The sequelae of severe hypercalcemia together with direct complications from tumor dissemination in patients with advanced disease are usually fatal. Due to its rarity, formal studies to guide the diagnosis and management of parathyroid carcinoma are lacking. However, recent data from case reports, case series, and registry studies suggest the emergence of new and effective treatment approaches for this understudied disease. We reviewed existing literature on the diagnosis and management of parathyroid carcinoma. Our findings suggest that traditional approaches such as surgical resection for both localized and metastatic diseases continue to play an important role in patient management. For patients with unresectable disease, newer systemic treatment approaches, including the use of temozolomide and tyrosine kinase inhibitors, may offer clinical benefit.

The Role of Demographic and Clinical Factors in Germline Mutation Testing for Patients with Primary Hyperparathyroidism

INTRODUCTION

Guidelines recommending genetic counseling in primary hyperparathyroidism (PHPT) vary. To further delineate current recommendations, this study examined genetic counseling referral patterns and rates of mutations in surgical patients with PHPT.

PATIENTS AND METHODS

A single-institution review was performed of adult patients who underwent parathyroidectomy for presumed sporadic PHPT. Genetic testing indications of hypercalcemia onset ≤ 40 years, multigland disease (MGD), family history (FHx) of PHPT, or other clinical indications suspicious for a PHPT-related endocrinopathy were examined by demographics and mutation detection rates.

RESULTS

Genetic counseling was performed in 237 (37.9%) of 625 patients. Counseling was discussed but not performed in 121 (19.4%) patients. No evidence was noted of genetic referral discussion in the remaining 267 (42.7%). Of these groups, patients who received genetic counseling were youngest, p < 0.001 [median age 55.3 (IQR 43.2, 66.7) years]. The majority of patients with indications of age ≤ 40 years (65.7%), FHx (78.0%), and other clinical indications (70.7%) underwent genetic counseling, while most with MGD (57.0%) did not. Eight mutations were detected in 227 patients (3.5%). Mutations included: MEN1 (n = 2), CDC-73 (n = 4), and CASR (n = 2). Detection was most common in patients with FHx (4/71, 5.6%), then age ≤ 40 years (3/66, 4.5%), and other clinical indications (3/80, 3.8%). No mutations were identified in 48 patients tested solely for MGD.

CONCLUSIONS

Most patients with onset of hypercalcemia age ≤ 40 years, positive FHx, or other clinical concerns underwent genetic counseling, while most with MGD did not. As no germline mutations were identified in patients with MGD alone, further investigation of MGD as a sole indication for genetic counseling may be warranted.

Generation of induced pluripotent stem cell line (MIPTi002-A) derived from a patient with a heterozygous type mutation in the CDC73 gene

CDC73-related disorders are inherited in an autosomal dominant manner. An individual with a CDC73-related disorder may have inherited the disorder from an affected parent or developed it as the result of a de novo pathogenic variant of CDC73. The iPSC line was obtained by reprogramming the PBMCs of a patient with a heterozygous type mutation of the CDC73 gene. This cell line could be useful to scrutinize and study the development of CDC73-associated parathyroid carcinoma.

Craniofacial disorders and dysplasias: Molecular, clinical, and management perspectives

There is a wide spectrum of craniofacial bone disorders and dysplasias because embryological development of the craniofacial region is complex. Classification of craniofacial bone disorders and dysplasias is also complex because they exhibit complex clinical, pathological, and molecular heterogeneity. Most craniofacial disorders and dysplasias are rare but they present an array of phenotypes that functionally impact the orofacial complex. Management of craniofacial disorders is a multidisciplinary approach that involves the collaborative efforts of multiple professionals. This review provides an overview of the complexity of craniofacial disorders and dysplasias from molecular, clinical, and management perspectives.

[Special features of the diagnostics and treatment of hereditary primary hyperparathyroidism]

Between 2% and 10% of patients with primary hyperparathyroidism (pHPT) are diagnosed with hereditary forms of primary hyperparathyroidism (hpHPT). They are more prevalent in younger patients before the age of 40 years, in patients with persistence or recurrence of pHPT and pHPT patients with multi-glandular disease (MGD). The various forms of hpHPT diseases can be classified into four syndromes, i.e., hpHPT associated with diseases of other organ systems, and four diseases that are confined to the parathyroid glands. Approximately 40% of patients with hpHPT suffer from multiple endocrine neoplasia type 1 (MEN-1) or show germline mutations of the MEN‑1 gene. Currently, germline mutations that lead to a specific diagnosis in patients with hpHPT have currently been described in 13 different genes, which enables a clear diagnosis of the disease; however, a clear genotype-phenotype correlation does not exist, even though the complete loss of a coded protein (e.g. due to frame-shift mutations in the calcium sensing receptor, CASR) often leads to more severe clinical consequences than merely a reduced function of the protein (e.g. due to point mutation). As the various hpHPT diseases require different treatment approaches, which do not correspond to that of sporadic pHPT, a clear definition of the specific form of hpHPT must always be strived for. Therefore, before surgery of a pHPT with clinical, imaging or biochemical suspicion of hpHPT, genetic proof or exclusion of hpHPT is necessary. The differentiated treatment approach for hpHTP can only be defined by taking the clinical and diagnostic results of all the abovenamed findings into account.

Rare duplication of the CDC73 gene and atypical hyperparathyroidism-jaw tumor syndrome: A case report and review of the literature

BACKGROUND

Hyperparathyroidism jaw-tumor syndrome (HPT-JT) is the rarest familial cause of primary hyperparathyroidism, with an incidence <1/1000000, caused by a pathogenic variant in the CDC73 (or HRPT2) gene that encodes parafibromin, a protein involved in many cellular mechanisms. Patients with HPT-JT have a 15-20% of risk of developing parathyroid carcinoma, whereas it accounts for only 1% of all cases of primary hyperparathyroidism. Patients also develop jaw tumors in 30% of cases, kidney abnormalities in 15% of cases, and uterine tumors in 50% of patients.

CASE REPORT

Here are report two atypical cases of HPT-JT with variable expressivity in the same family. In front of an isolated primary hyperparathyroidism at 28 years of age of incidental discovery following a weight gain, the propositus benefited a first-line panel by Next-Generation Sequencing of the genes involved in familial hyperparathyroidism: CaSR, CDC73, MEN1, and RET. Genetic testing revealed the presence of a pathogenic germline variation CDC73: c.687_688dup; p.Val230Glufs*28, found only in nine families in the literature and allowing the diagnosis of HPT-JT. Given a history of primary hyperparathyroidism at 52 years and adenomyosis, the patient's mother also underwent a genetic analysis that found her daughter's variation and established her inherited trait.

CONCLUSION

In view of the clinical and genotypic heterogeneity, we confirm the interest of using an extended gene panel for the diagnosis of familial primary hyperparathyroidism. CDC73 variations could be more frequent than described in the literature. The association of primary hyperparathyroidism with uterine involvement could be a new indication for analysis.

Multiple endocrine neoplasia type 2 (MEN2) and RET specific modifications of the ACMG/AMP variant classification guidelines and impact on the MEN2 RET database

The Multiple Endocrine Neoplasia type 2 (MEN2) RET proto-oncogene database, originally published in 2008, is a comprehensive repository of all publicly available RET gene variations associated with MEN2 syndromes. The variant-specific genotype/phenotype information, age of earliest reported medullary thyroid carcinoma (MTC) onset, and relevant references with a brief summary of findings are cataloged. The ACMG/AMP 2015 consensus statement on variant classification was modified specifically for MEN2 syndromes and RET variants using ClinGen sequence variant interpretation working group recommendations and ClinGen expert panel manuscripts, as well as manuscripts from the American Thyroid Association Guidelines Task Force on Medullary Thyroid Carcinoma and other MEN2 RET literature. The classifications for the 166 single unique variants in the MEN2 RET database were reanalyzed using the MEN2 RET specifically modified ACMG/AMP classification guidelines (version 1). Applying these guidelines added two new variant classifications to the database (likely benign and likely pathogenic) and resulted in clinically significant classification changes (e.g., from pathogenic to uncertain) in 15.7% (26/166) of the original variants. Of those clinically significant changes, the highest percentage of changes, 46.2% (12/26), were changes from uncertain to benign or likely benign. The modified ACMG/AMP criteria with MEN2 RET specifications will optimize and standardize RET variant classifications.

Identification of 4 New Loci Associated With Primary Hyperparathyroidism (PHPT) and a Polygenic Risk Score for PHPT

CONTEXT

A hypothesis-free genetic association analysis has not been reported for patients with primary hyperparathyroidism (PHPT).

OBJECTIVE

We aimed to investigate genetic associations with PHPT using both genome-wide association study (GWAS) and candidate gene approaches.

METHODS

A cross-sectional study was conducted among patients of European White ethnicity recruited in Tayside (Scotland, UK). Electronic medical records were used to identify PHPT cases and controls, and linked to genetic biobank data. Genetic associations were performed by logistic regression models and odds ratios (ORs). The combined effect of the genotypes was researched by genetic risk score (GRS) analysis.

RESULTS

We identified 15 622 individuals for the GWAS that yielded 34 top single-nucleotide variations (formerly single-nucleotide polymorphisms), and LPAR3-rs147672681 reached genome-wide statistical significance (P = 1.2e-08). Using a more restricted PHPT definition, 8722 individuals with data on the GWAS-identified loci were found. Age- and sex-adjusted ORs for the effect alleles of SOX9-rs11656269, SLITRK5-rs185436526, and BCDIN3D-AS1-rs2045094 showed statistically significant increased risks (P < 1.5e-03). GRS analysis of 5482 individuals showed an OR of 2.51 (P = 1.6e-04), 3.78 (P = 4.0e-08), and 7.71 (P = 5.3e-17) for the second, third, and fourth quartiles, respectively, compared to the first, and there was a statistically significant linear trend across quartiles (P < 1.0e-04). Results were similar when stratifying by sex.

CONCLUSION

Using genetic loci discovered in a GWAS of PHPT carried out in a Scottish population, this study suggests new evidence for the involvement of genetic variants at SOX9, SLITRK5, LPAR3, and BCDIN3D-AS1. It also suggests that male and female carriers of greater numbers of PHPT-risk alleles both have a statistically significant increased risk of PHPT.

Parathyroid carcinoma presenting with ventricular bigeminy in pregnancy

Parathyroid carcinoma is very rare in pregnancy. Clinical features are similar to primary hyperparathyroidism. A 38-year-old pregnant woman had repeated hospital admissions for palpitations, headaches, dizziness and polydipsia. Blood investigations showed severe hypercalcaemia with raised parathyroid hormone and 24-hour ECG showed ventricular bigeminy and premature ventricular contractions. Neck ultrasound showed a lesion in the right thyroid lobe. Consequently, she underwent an en bloc resection of the right parathyroid and thyroid lobe at 23 weeks gestation. Histology results confirmed parathyroid cancer. This case highlights the complexities of identifying hypercalcaemia in pregnancy due to the overlapping features with common disorders of pregnancy. Early recognition and timely surgical management can prevent maternal and fetal complications. Also, the case demonstrates the value of interprofessional collaboration between different specialities in providing quality care and improving outcomes. An abridged version of this case was presented at European Congress of Endocrinology 2021.

Mathematical model for preoperative differential diagnosis for the parathyroid neoplasms

Background and objective

Methods

Results

Conclusions

Hereditary Endocrine Tumors and Associated Syndromes: A Narrative Review for Endocrinologists and Endocrine Surgeons

OBJECTIVE

Hereditary endocrine tumors (HET) were among the first group of tumors where predisposition syndromes were recognized. The utility of genetic awareness is having the capacity to treat at an earlier stage, screen for other manifestations and initiate family cascade testing. The aim of this narrative review is to describe the most common hereditary syndromes associated with frequently encountered endocrine tumors, with an emphasis on screening and surveillance.

METHODS

A MEDLINE search of articles for relevance to endocrine tumors and hereditary syndromes was performed.

RESULTS

The most common hereditary syndromes associated with frequently encountered endocrine tumors are described in terms of prevalence, genotype, phenotype, penetrance of malignancy, surgical management, screening and surveillance.

CONCLUSION

Medical practitioners involved in the care of patients with endocrine tumors, should have an index of suspicion for an underlying hereditary syndrome. Interdisciplinary care is integral to successful, long-term management of these patients and affected family members.

RET Regulates Human Medullary Thyroid Cancer Cell Proliferation through CDK5 and STAT3 Activation

Medullary thyroid cancer (MTC) is a neuroendocrine tumor that arises from the parafollicular C-cells, which produces the hormone calcitonin. RET is a transmembrane receptor protein-tyrosine kinase, which is highly expressed in MTC. Our previous studies reported that cyclin-dependent kinase 5 (CDK5) plays a crucial role in cancer progression, including MTC. However, the role of CDK5 in GDNF-induced RET signaling in medullary thyroid cancer proliferation remains unknown. Here, we investigated RET activation and its biochemically interaction with CDK5 in GDNF-induced medullary thyroid cancer proliferation. Our results demonstrated that GDNF stimulated RET phosphorylation and thus subsequently resulted in CDK5 activation by its phosphorylation. Activated CDK5 further caused STAT3 activation by its specific phosphorylation at Ser727. Moreover, we also found that GDNF treatment enhanced ERK1/2 and EGR1 activity, which is involved in p35 activation. Interestingly, we identified for the first time that CDK5 physically interacted with RET protein in MTC. Overall, our results provide a new mechanism for medullary thyroid cancer cell proliferation, suggesting that targeting CDK5 may be a promising therapeutic candidate for human medullary thyroid cancer in the near future.

Hyperparathyroidism-Jaw Tumor Syndrome

Primary hyperparathyroidism is a relatively common endocrine disorder, affecting 7 out of 1,000 adults. The median age at onset is the 6th decade of life. Our objective was to present a young patient with primary hyperparathyroidism who has a positive CDC73 mutation. A 23-year-old woman was evaluated for hypercalcemia that was found after surgery for bilateral ovarian cyst removal. Her family history included multiple family members with nephrolithiasis. The physical examination revealed a well-appearing Caucasian woman with no palpable neck mass. The laboratory results showed serum calcium at 11.7 mg/dL (ref. 8.4–10.2), ionized calcium at 1.44 mmol/L (ref. 1.12–1.32), and serum PTH at 192 pg/mL (ref. 11–65). A technetium-99 sestamibi scan revealed focal uptake inferior to the left thyroid lobe. Thyroid ultrasound showed a left parathyroid adenoma. The patient subsequently underwent left inferior parathyroidectomy, which confirmed parathyroid adenoma, with resultant normalization of serum calcium and PTH levels. Due to her young age at diagnosis, genetic testing was performed, which revealed a mutation of CDC73. Although penetrance and expression are variable, the CDC73 mutation is associated primarily with hyperparathyroidism-jaw tumor syndrome, familial isolated hyperparathyroidism, and sporadic parathyroid carcinoma. This patient currently has no evidence of jaw, uterine or renal tumors on screening imaging. Given the potential impact of inheritable neoplasia, all young patients with unexplained hyperparathyroidism should be considered for genetic screening.

Overview of Genetically Determined Diseases/Multiple Endocrine Neoplasia Syndromes Predisposing to Endocrine Tumors

In this chapter, we present an overview of multiple endocrine neoplasia syndromes including their most important clinical and molecular features. Multiple endocrine neoplasia type 1 and 2 syndromes (MEN1 and MEN2) are discussed in detail. Syndromes that are presented in other chapters are only briefly mentioned. We discuss the relevance of germline gene alterations in apparently sporadic endocrine tumors, e.g., medullary thyroid cancer, primary hyperparathyroidism, and neuroendocrine tumors. McCune-Albright syndrome that only exists in non-hereditary, sporadic forms is also discussed in detail, as tumors of several endocrine organs can develop in the same individual.

Genetische Nierensteinerkrankungen

Die Inzidenz und Prävalenz von Steinerkrankungen haben in den letzten Jahren deutlich zugenommen. Es ist von entscheidender Bedeutung, möglichst frühzeitig eine richtige Diagnose der zugrunde liegenden Erkrankung zu stellen, um die richtige Therapie einzuleiten und damit möglicherweise schwerwiegende Folgen, wie terminales Nierenversagen, zu verhindern. Bei Kindern lassen sich in ca. 75 % der Fälle genetische oder anatomische Ursachen identifizieren. Die verschiedenen zugrunde liegenden Erkrankungen für die jeweiligen lithogenen Risikofaktoren werden hier präsentiert und die entsprechenden Therapieoptionen, sofern vorhanden, erläutert.

Genetics of parathyroids disorders: Overview

Several familial forms of primary hyperparathyroidism (PHTP) have been discovered over the past 25 years, and molecular test for their risk assessment has been widely increasing. These syndromic and non-syndromic forms have received benefits from the identification of the responsible genes whose mutations account for the genetic susceptibility to develop parathyroid tumours as also other endocrine and nonendocrine tumours. In recent years, care options have been made available to patients and families with hereditary PHPT, and the process of systematically assessing the genetic risk has been becoming increasingly important. The aim of this review is to help health providers not frequently dealing with genetic testing use, introducing general concepts with regard to genetic diagnosis issues. The role and the practical usefulness of DNA-based diagnosis in patients affected by different forms of "congenital" PHPT is described, closely looking on why, when and how genetic testing should be performed in these subjects and their relatives. Moreover, this review will provide some practical suggestions and recommendations concerning on how to deal with a suspected or known case of familial PHPT.

CDC73-Related Disorders: Clinical Manifestations and Case Detection in Primary Hyperparathyroidism

CONTEXT

Heterozygous pathogenic germline variants in CDC73 predispose to the development of primary hyperparathyroidism (pHPT) and, less frequently, ossifying fibroma of the jaw and renal and uterine tumors. Clinical information on CDC73-related disorders has so far been limited to small case series.

OBJECTIVE

To assess the clinical manifestations and penetrance in CDC73-related disorders and to improve case detection in pHPT.

DESIGN

Nationwide retrospective Dutch cohort study.

SETTING

Tertiary referral center.

PATIENTS

We studied 89 patients with pHPT referred for germline CDC73 analysis and 43 subsequently tested relatives who proved to be mutation carriers.

INVESTIGATION

Germline CDC73 mutation analysis.

MEAN OUTCOME

CDC73 mutation detection yield, referral rate, and CDC73-related disease penetrance.

RESULTS

Pathogenic germline CDC73 variants were identified in 11 of the 89 referred pHPT patients (12.4%), with (suspected) hyperparathyroidism-jaw tumor (HPT-JT) syndrome (n = 3), familial isolated pHPT (n = 5), apparently sporadic parathyroid carcinoma (n = 2), and apparently sporadic parathyroid adenoma (n = 1). The estimated penetrance of CDC73-related disorders was 65% at age 50 years (95% confidence interval, 48% to 82%) in 43 nonindex mutation carriers.

CONCLUSIONS

Germline CDC73 analysis is recommended in individuals with (suspected) HPT-JT syndrome, familial isolated pHPT, atypical or malignant parathyroid histology, and young individuals with pHPT. These criteria would increase germline CDC73 mutation detection, enabling optimal clinical management of pHPT as well as genetic counseling and surveillance for family members at risk for developing CDC73-related disorders.