Molecular and Clinical Spectrum of Primary Hyperparathyroidism

The Landmark Series: Management of Primary Hyperparathyroidism

Surgery is the only definitive treatment for primary hyperparathyroidism (PHPT). The surgical management of PHPT has evolved over the past several decades in response to the continually growing body of evidence supporting its effectiveness in both symptomatic and asymptomatic disease. As imaging modalities for localization, operative approach, and intraoperative adjuncts, such as intraoperative parathyroid hormone testing, have been optimized, careful evaluation of the timing of parathyroidectomy in relationship to the disease's natural history has been pursued to limit the detrimental end-organ effects of untreated PHPT. Herein, we review select studies examining key aspects of PHPT management fundamental to the practicing surgical oncologist and endocrine surgeon caring for patients with PHPT.

Hyperparathyroidism-Jaw Tumor Syndrome: A Case Diagnosed After the Removal of Multiple Ossifying Fibromas of the Jaws

Hyperparathyroidism-jaw tumor syndrome (HPT-JT) is a hereditary neoplastic disorder caused by a pathogenic variant in the CDC73 tumor suppressor gene. It is characterized by increased values of PTH, ossifying fibromas of the jaws, and in some cases neoplasms of the kidneys/or the uterus. We present a case of a 65-year-old male who had several jaw tumors with secondary infection requiring treatment. Previous medical history included parathyroid adenomas with a long history of increased PTH and kidney tumor. This prompted genetic testing, which confirmed a heterozygous CDC73 pathogenic variant, establishing the diagnosis of HPT-JT. The jaw tumor was excised. The patient was referred to genetic counselling but declined.

An Analysis of Primary Hyperparathyroidism in Individuals Diagnosed with Multiple Endocrine Neoplasia Type 2

Background: Primary hyperparathyroidism (PHPT) represents a multi-faced disease with a wide spectrum of manifestations. Familial forms of PHPT (affecting up to 10% of the cases) involve a particular category that encompasses a large range of hereditary syndromes, including parathyroid hyper-function, frequently in the setting of a multi-glandular disease. Objective: The aim was to analyze the most recent findings regarding PHPT in multiple endocrine neoplasia type 2 (MEN2) to a better understanding of the timing with respect to the associated ailments, MEN2-related PHPT (MEN2-PHPT) clinical and genetic particularities, optimum diagnostic, and overall management, particularly, surgical outcomes. Methods: This was a PubMed-based compressive review with regard to the latest data published in English from January 2020 until January 2025, using the following keywords: "primary hyperparathyroidism" and "multiple endocrine neoplasia", "multiple endocrine neoplasia type 2", "MEN2", or "MEN2A". We included original full-length studies of any study design that provided clinically relevant data in MEN2-PHPT and excluded reviews, meta-analysis, and case reports/series. Results: A total of 3783 individuals confirmed with MEN2 or RET pathogenic variants carriers were analyzed across 14 studies that provided data on PHPT. The prevalence of MEN2-PHPT subjects varied between 7.84% and 31.3%, with particularly low rates in non-index patients (3.8%). PHPT was the first syndrome manifestation in 0.9% of MEN2 patients. In terms of gender distribution, females represented 42.85% or 54.9% (similar rates between women and men, and only a single cohort showed a female rate up to 80%). Most subjects were diagnosed with PHPT and underwent surgery in the third or fourth decade of life. The highest median age at MEN2 diagnosis was 42 years. The youngest patients were RET pathogenic variants carriers who underwent (genetic) screening with median ages of 12 or 14 years. RET pathogenic variants analysis (n = 10/14 studies) showed that 16.67% of patients with p.Cys634Arg and 37.5% of those with p.Cys611Tyr had symptomatic PHPT, while those with p.Cys618Phe and p.Leu790Phe were asymptomatic. Timing analysis with respect to the medullary thyroid carcinoma diagnosis showed synchronous PHPT diagnosis in 80% and metachronous in 10% of MEN2 patients; with respect to MEN2-pheochromocytoma, synchronous diagnosis of PHPT was found in 56%, while pheochromocytoma was identified before PHPT in 22% of the cases and after PHPT in 22%. Studies (n = 10/14, N = 156 subjects with MEN2-PHPT) on parathyroidectomy identified that 72.7% to 100% of the individuals underwent surgery, typically performed in adulthood, at ages spanning from a mean of 34.7 to 48.5 years. The post-surgery outcomes varied (e.g., the rate for persistent PHPT was of 0%, 8% to 16.7%; recurrent PHPT of 12.5% to 23%; permanent hypoparathyroidism of 33% to 46%; permanent unilateral vocal cord palsy of 0% up to16.7%). Data regarding the number of involved glands (n = 7, N = 77): the prevalence of multi-glandular disease was pinpointed between 12.5% and 50%. Conclusions: MEN2-PHPT involved unexpected high rates of single-gland involvement (from 33.3% to 87.5%), probably due to an early detection across genetic screening. Traditional female higher prevalence in PHPT was not confirmed in most MEN2 cohorts. As expected, a younger age at PHPT diagnosis and surgery than seen in non-MEN2 patients was identified, being tidily connected with the syndromic constellation of tumors/malignancies. Overall, approximately, one out of ten patients were further confirmed with MEN2 starting with PHPT as the first clinically manifested element.

Genotype-Phenotype Correlations in the Hyperparathyroidism-Jaw Tumor Syndrome

Establishing genotype-phenotype correlations in disorders of hereditary endocrine neoplasia is important for clinical screening, genetic counseling, prognostication, surveillance, and surgical strategy, and may also provide clues about disease pathogenesis. Important genotype-phenotype correlations are recognized, for example, in pheochromocytoma/paraganglioma and multiple endocrine neoplasia type 2A. The presence of such correlations has been less clear in other familial endocrine disorders associated with primary hyperparathyroidism including multiple endocrine neoplasia type 1, and the hyperparathyroidism-jaw tumor syndrome (HPT-JT). Characteristic features of HPT-JT, apart from fibro-osseous jaw tumors and uterine lesions, include renal neoplasms, such as Wilms tumor and mixed epithelial and stromal tumor ("renal hamartomas"), and a high incidence of parathyroid cancer. Emerging evidence suggests two different genotype-phenotype correlations in HPT-JT based on the type of variant in the CDC73 tumor suppressor gene. Although multiple CDC73 genotypes can give rise to the Wilms tumor phenotype in HPT-JT, the development of mixed epithelial and stromal tumor of the kidney specifically correlates with the presence of a start-loss variant affecting the initiator methionine codon of parafibromin, the protein product encoded by CDC73. Furthermore, the risk of parathyroid cancer in HPT-JT also appears to correlate with genotype: CDC73 frameshift indel, splice-site, and stop-gain genotypes are associated with a greatly increased risk of parathyroid carcinoma compared to carriers of CDC73 missense and nonframeshift indel variants. The recognition of such genotype-phenotype correlations in HPT-JT may impact genetic counseling, patient care and disease surveillance.

Adolescent primary hyperparathyroidism

Adolescent primary hyperparathyroidism (PHPT) is a rare endocrine disorder bearing distinctions from the adult form. This review examines its unique aspects, focusing on clinical presentation, genetic etiologies, genotype-phenotype correlations, and therapeutic management. Adolescent PHPT often has a genetic basis, whether familial, syndromic, or apparently sporadic, and identifying the underlying genetic cause is important for patient care. The clinical presentation is predominantly symptomatic worldwide. Unique manifestations in this age group include rickets, short stature, and slipped capital femoral epiphysis. Genotype-specific differences are evident in the adolescent PHPT characteristics. Diagnostic evaluation requires careful interpretation of biochemical and dual-energy X-ray absorptiometry findings using age and gender-specific reference ranges, with targeted screening for syndrome-associated neoplasms. Surgery remains the cornerstone of management. Current knowledge gaps in their management include treatment protocols for multiple endocrine neoplasia type 1-associated PHPT, the efficacy and safety of nonsurgical options, and long-term post-surgical outcomes.

Molecular basis of symptomatic sporadic primary hyperparathyroidism: New frontiers in pathogenesis

Primary hyperparathyroidism is a common endocrine disorder characterized by inappropriate elevation of parathyroid hormone and hypercalcemia. While predominantly an asymptomatic disease in Western populations, symptomatic presentations are more prevalent in Eastern countries. The molecular pathogenesis of sporadic PHPT primarily involves genetic and epigenetic alterations leading to abnormal parathyroid cell proliferation and altered calcium sensing mechanism. To date, MEN1 and cyclin D1 are the only established drivers of sporadic PHPT. Somatic MEN1 gene mutations occur in 30-40 % of sporadic parathyroid adenomas (PA), with a recent study on symptomatic cases reporting germline variants.Cyclin D1 overexpression in sporadic PA has been observed in 20-40 % of cases in Western populations and 80 % of cases in Eastern populations, with an inverse association with cyclin-dependent kinase inhibitors CDKN2A and CDKN2B expression. The calcium-sensing receptor expression was significantly lower in symptomatic compared to asymptomatic PHPT, strongly supported by epigenetic deregulation (promoter hypermethylation and histone methylation). Recent studies have highlighted the potential involvement of EZH2, a histone methyltransferase, in parathyroid tumorigenesis. Additionally, parathyroid-specific transcription factors like GCM2, PAX1, and GATA3 are emerging as putative tumor suppressors, especially from the symptomatic PHPT. Next-generation sequencing has identified novel potential drivers such as PIK3CA, MTOR, and NF1 in sporadic PC, alongside CDC73. The molecular landscape of sporadic PHPT appears to differ between Eastern and Western populations. This heterogeneity underscores the need for further large-scale studies, particularly in symptomatic cases from developing nations, to comprehensively elucidate the molecular drivers of parathyroid tumorigenesis.

Heritable hyperparathyroidism: Genetic insights and clinical implications

Familial or heritable hyperparathyroidism (FHPT) is seen in approximately 10-15 % of patients with primary hyperparathyroidism (PHPT). Once the diagnosis of PHPT is established, consideration of heritable forms should be made in patients with positive family history, young onset, multi-glandular disease, and recurrent or persistent disease. FHPT encompasses both syndromic and non-syndromic forms. Syndromic forms include multiple endocrine neoplasia (MEN) types 1, 2, 3 and 4, hyperparathyroidism-jaw tumor syndrome, hereditary pheochromocytoma and paraganglioma, and the more recently reported, Birt-Hogg-Dubé (BHD) syndrome, and X-linked intellectual disability syndrome. Non-syndromic forms include familial hypocalciuric hypercalcemia (FHH)- types 1,2, and 3, neonatal severe hyperparathyroidism, GCM2-mediated hyperparathyroidism, transient neonatal hyperparathyroidism, and familial isolated hyperparathyroidism. In this review we aim to review the heritable forms of PHPT and highlight the important genetics insights and clinical implications.

Association of primary hyperparathyroidism with pituitary adenoma and management issues

The co-occurrence of primary hyperparathyroidism (PHPT) and pituitary adenomas (PAs) is often indicative of underlying genetic syndromes such as Multiple Endocrine Neoplasia type 1 (MEN1) and, less commonly, MEN4. Although both conditions can occur sporadically, their simultaneous presence warrants evaluation for genetic mutations, with MEN1 mutations being the most frequent cause. The management of concurrent PHPT and PAs, especially in MEN1 patients, presents unique challenges. Management complexities arise from the syndromic nature, involving both surgical and medical interventions tailored to each condition. PHPT often manifests earlier and more aggressively in MEN1, requiring surgical intervention. However, recurrence rates remain high due to multiglandular involvement. Pituitary adenomas in MEN1 are primarily prolactinomas, and treatment with dopamine agonists results in significant tumour control in most cases. Overall, PAs associated with MEN1 are generally responsive to medical therapy, but careful long-term monitoring is essential. The utility of genetic screening cannot be overstated, as it aids in early detection, risk stratification, and management of both the index case and affected family members by cascade screening. A multidisciplinary approach is crucial for optimizing outcomes, with ongoing surveillance to manage recurrence and associated complications. In summary, the co-occurrence of PHPT and PAs, particularly in the context of MEN1, necessitates an integrated management strategy. Genetic testing is key in confirming diagnosis and guiding treatment, while surgical and medical interventions should be tailored to the extent and nature of glandular involvement. Close monitoring for recurrence and proactive family screening are essential components of long-term care.

Chapter 10: What parathyroid imaging is required for hyperparathyroidism?

In over 80% of cases, primary hyperparathyroidism results from hypersecretion of PTH by a single parathyroid adenoma. Multi-glandular involvement, combining adenoma and/or hyperplasia in varying proportions, is also possible, although less frequent. When the diagnosis of hyperparathyroidism is certain and surgery is envisaged, imaging is useful for locating the hyperfunctioning gland or glands. First-line exploration is based on a parathyroid ultrasound and a nuclear medicine examination, which may be parathyroid scintigraphy, preferably double isotope I/12399m Tc-sestamibi, with planar and tomoscintigraphic acquisitions, or a PET-CT scan with 18F-choline. In the event of negative results, it is advisable to perform a choline PET scan if the initial examination was scintigraphy. In difficult situations, additional investigations using 4D parathyroid CT or parathyroid MRI, fine-needle aspiration cytology and determination of PTH in the flushing fluid are possible after multidisciplinary discussion in an expert center.

Chapter 6: Syndromic primary hyperparathyroidism

Syndromic primary hyperparathyroidism has several features in common: younger age at diagnosis when compared with sporadic primary hyperparathyroidism, often synchronous or metachronous multi-glandular involvement, higher possibility of recurrence, association with other endocrine or extra-endocrine disorders, and suggestive family background with autosomal dominant inheritance. Hyperparathyroidism in multiple endocrine neoplasia type 1 is the most common syndromic hyperparathyroidism. It is often asymptomatic in adolescents and young adults, but may be responsible for recurrent lithiasis and/or bone loss. Hyperparathyroidism-jaw tumor syndrome is less frequent, but often immediately symptomatic, with higher blood calcium levels, and is sometimes associated with an atypic parathyroid tumor or parathyroid carcinoma. Hyperparathyroidism in multiple endocrine neoplasia type 2A is not at the forefront of the clinical picture, rarely revealing the disease, and often manifests with few symptoms. Multiple endocrine neoplasia type 4 is a more recently described entity, in which hyperparathyroidism seems to occur later and be less severe than in previous syndromes. In all cases, the indications and modalities of surgical treatment should be discussed in an expert center. The risk of recurrence after surgery, particularly high in multiple endocrine neoplasia type 1, requires long-term monitoring.

Primary Hyperparathyroidism in MEN2 Syndromes

One of the components of the classical form of MEN2 syndromes is primary hyperparathyroidism (PHP). It occurs in 20-30% of the typical MEN2A syndrome. Recently, the prevalence in ret gene carriers is rarer possibly due to the increased recognition of cases who have familial MTC only. PHP is diagnosed more frequently in association with the exon 11, 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 is after the third 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.

Demineralization of Osseous Structures as Presentation of a Rare Genetic Disorder That Is Associated With a High Rate of Mortality

Objectives: Describe the details of the clinical presentation, diagnostic challenges, and management of a female neonate with neonatal severe hyperparathyroidism (NSHPT). Methods: This case report was developed from a retrospective chart review. The female infant was born to consanguineous parents-first cousins, with multiple prenatal concerns, including gestational diabetes, intrauterine growth restriction, polyhydramnios, and suspicion of a hypoplastic left atrium on prenatal echocardiogram (ECHO). Following a planned C-section at 37 weeks gestation, the neonate exhibited moderate respiratory distress with subcostal retractions. On physical examination, craniotabes, a bell-shaped chest, and a continuous machinery-type murmur were noted. Results: Evaluation at birth revealed a large Patent Ductus Arteriosus and significant demineralization of skeletal structures with atypical rib morphology. Lab work at 24 h of life (HOL) showed elevated serum calcium level (14.3 mg/dL), ionized calcium-iCal (2.32 mmol/L), and normal 25-OH Vitamin D (54.2 ng/mL). A comprehensive skeletal survey uncovered generalized osteopenia, metaphyseal lucencies, and evidence of healing fractures. Repeat lab work at 43 HOL, showed serum calcium of 18.0 mg/dL, iCal 2.67 mmol/L, and elevated parathyroid hormone (PTH) of 2116 pg/mL. Diagnosis of NSHPT was established based on laboratory findings. Molecular testing confirmed a homozygous variant (c.1744T >A; p.Cys582Ser) in the calcium-sensing receptor (CaSR) gene which confirmed the diagnosis of NSHPT. NSHPT, a rare genetic disorder associated with high mortality rates, is often caused by inactivating CaSR gene variants. The patient's family history revealed a strong correlation with familial hypocalciuric hypercalcemia (FHH), a benign condition associated with asymptomatic hypercalcemia, normal to minimally elevated parathyroid level, and hypocalciuria, it is caused by heterozygous inactivating mutations in the CaSR gene. Treatment of NSHPT typically involves total or subtotal parathyroidectomy; however, initial medical intervention is often necessary. In this case, the neonate underwent medical treatment with calcitonin, furosemide to help facilitate renal clearance of calcium, and intravenous fluids before a successful parathyroidectomy. Conclusions: This case accentuates the importance of considering rare genetic disorders in neonates with complex clinical presentations and affirms the need for comprehensive counseling and education, particularly in consanguineous parents, to address familial implications and guide appropriate interventions.

Somatostatin Receptor Imaging in the Diagnosis and Management of Parathyroid Neuroendocrine Neoplasia

BACKGROUND

Parathyroid tumors are classified as parathyroid neuroendocrine neoplasia (NEN) by the IARC-WHO classification. These tumors can occur with NENs from other sites, which often require total-body [68Ga]-DOTA-peptides PET/CT. This study aimed to assess the utility of [68Ga]-DOTA-peptide PET/CT in imaging parathyroid NENs and to evaluate the underlying mechanisms.

METHODS

Fifty patients with primary hyperparathyroidism (PHPT) and parathyroid NENs histologically confirmed as parathyroid adenomas (PAs) were included. PET/CT with [68Ga]-DOTA-peptide was performed in 16 patients with localized PAs, including 10 with MEN1 syndrome. Somatostatin receptor types 2 and 5 (SST2 and SST5) staining was performed on PAs from 48 patients. Somatostatin analogs (SSA) were prescribed in four patients with MEN 1 syndrome and 1 with persistent acromegaly, all with PAs and PHPT. The therapy effects on calcium and parathyroid hormone (iPTH) were evaluated.

RESULTS

[68Ga]-DOTA-peptide PET/CT detected 20 PAs with high radiopharmaceutical uptake. SST2 expression was negative on PA cell membranes in all cases and positive on endothelium in 39 (81%) PAs. Membrane SST5 expression was positive in 25 (52%) PAs and endothelial was positive in 40 (83%). Serum calcium levels decreased in patients on SSA therapy, while iPTH did not.

CONCLUSIONS

PET/CT with [68Ga]-DOTA-peptides can detect parathyroid NENs. The incidental detection of high [68Ga]-DOTA-peptide uptake in the parathyroid region during whole-body PET/CT may prompt biochemical evaluation for PHPT. We suggest that endothelial SST expression mediates high radiopharmaceutical uptake by PAs and that SSA treatment can reduce hypercalcemia in PHPT patients.

18F-Fluorocholine-Positron Emission Tomography/Computerized Tomography (FCH PET/CT) Imaging for Detecting Abnormal Parathyroid Glands: Indication, Practice, Interpretation and Diagnostic Performance

In patients with confirmed hyperparathyroidism (HPT) scheduled for surgical treatment, the preoperatory imaging permits to optimize the operatory protocol of parathyroidectomy (PTX), in particular by selecting those patients who can benefit from minimally invasive PTX (MIPTX). The MIPTX has the merit to shorten the operative time, incision length, and to reduce the operatory risks. With preoperative localization studies, the rate of PTX failure, in particular due to nonsuspected multiglandular or ectopic disease, has been profoundly decreased. The first cases of incidental localization of abnormal parathyroid glands (PTs) on FCH PET/CTs performed for another indication were reported more than one decade ago. Since then, significant amount of data from heterogeneous series of patients consistently confirmed better diagnostic performances of FCH PET/CT (sensitivity for detection of abnormal PT 97%, range 96%-98%) in comparison with other radiopharmaceuticals, ultrasonography or 4D-CeCT in localizing hyperfunctioning parathyroid glands (HFPTGs) in case of primary HPT. Utility of FCH PET/CT in case of renal HPT has been reported in fewer series. The article discusses and summarizes the bibliographic evidence on documented indications of FCH PET/CT in patients with HPT, its safety profile, the practice of FCH PET/CT and interpretation of FCH PET/CT findings, including potential interpretation pitfalls and tips to avoid them. Our real-world experience over 12 years reinforces published evidence supporting the use of FCH PET/CT as the first-line radionuclide imaging technique in patients with all types of HPT in whom surgery is an option.

Familial states of primary hyperparathyroidism: an update

BACKGROUND

Familial primary hyperparathyroidism (PHPT) includes syndromic and non-syndromic disorders. The former are characterized by the occurrence of PHPT in association with extra-parathyroid manifestations and includes multiple endocrine neoplasia (MEN) types 1, 2, and 4 syndromes, and hyperparathyroidism-jaw tumor (HPT-JT). The latter consists of familial hypocalciuric hypercalcemia (FHH) types 1, 2 and 3, neonatal severe primary hyperparathyroidism (NSHPT), and familial isolated primary hyperparathyroidism (FIHP). The familial forms of PHPT show different levels of PHPT penetrance, developing earlier and with multiglandular involvement compared to sporadic counterpart. All these diseases exhibit Mendelian inheritance patterns, and for most of them, the genes responsible have been identified. DNA testing for predisposing mutations is helpful in index cases or in individuals with a high suspicion of the disease. Early recognition of hereditary disorders of PHPT is of great importance for the best clinical and surgical approach. Genetic testing is useful in routine clinical practice because it will also involve appropriate screening for extra-parathyroidal manifestations related to the syndrome as well as the identification of asymptomatic carriers of the mutation.

PURPOSE

The aim of the review is to discuss the current knowledge on the clinical and genetic profile of these disorders along with the importance of genetic testing in clinical practice.

Navigating Diagnostic Challenges in Ectopic Parathyroid Adenomas: A Case Report

Ectopic parathyroid adenomas pose significant diagnostic and therapeutic challenges due to their atypical locations outside the usual anatomical boundaries of the parathyroid glands. These adenomas, which represent a small percentage of primary hyperparathyroidism cases, are often found in areas such as the mediastinum, thymus, or retroesophageal space. Their ectopic nature complicates diagnosis, as traditional neck imaging techniques may fail to localize these glands. We present the case of a 27-year-old female who initially presented with nausea, vomiting, severe hypercalcemia, and elevated parathyroid hormone (PTH) levels. Despite being advised to consult an endocrinologist, she experienced difficulty scheduling an appointment. Due to persistent symptoms and laboratory abnormalities, she was subsequently admitted to the hospital. Initial neck imaging failed to identify the parathyroid adenoma. However, subsequent imaging, including parathyroid scintigraphy, revealed an ectopic parathyroid adenoma located in the mediastinum. The patient underwent a successful robotically assisted thymectomy, guided by intraoperative PTH monitoring, which resulted in the resolution of hypercalcemia and normalization of PTH levels. This case underscores the importance of a comprehensive diagnostic approach when dealing with ectopic parathyroid adenomas. Parathyroid scintigraphy, in particular, proves to be a critical tool due to its high sensitivity in detecting ectopic glands. Moreover, our findings emphasize the need for a high index of suspicion for ectopic parathyroid adenomas, especially when conventional neck imaging is inconclusive in cases of hyperparathyroidism. Timely and accurate diagnosis is essential for facilitating precise surgical intervention, ultimately leading to improved patient outcomes.

"Genetic tumor syndromes of the head and neck: Update in the genomic era"

Genetic tumor syndromes are due to inherited genetic mutations, which have recently come to the attention of clinicians due to the widespread adoption of DNA sequencing, ultimately leading to imaging for surveillance. As a result, radiologists must be familiar with the clinical, genetic, and radiologic features of these syndromes. This article reviews genetic tumor syndromes of the head and neck according to the recently updated WHO's 5th edition.

A Germline ZFX Missense Variant in a Patient With Primary Hyperparathyroidism

A 51-year-old woman with a history of primary hyperparathyroidism (PHPT) with prior parathyroidectomy, osteoporosis, and learning disability was referred for hypercalcemia discovered after a fall. Family history was negative for PHPT, pituitary, enteropancreatic neuroendocrine, or jaw tumors. Dysmorphic facies, multiple cutaneous melanocytic nevi, café au lait macules, long fingers, and scoliosis were observed. Laboratory evaluation showed an elevated parathyroid hormone (PTH) level, hypercalcemia, and hypophosphatemia, all consistent with PHPT. Preoperative imaging revealed a right inferior candidate parathyroid lesion. The patient underwent right inferior parathyroidectomy with normalization of PTH, calcium, and phosphorus. Genetic testing showed a likely pathogenic de novo heterozygous germline missense variant p.R764W in the ZFX gene that encodes a zinc-finger transcription factor previously shown to harbor somatic missense variants in a subset of sporadic parathyroid tumors. Germline variants in ZFX have been reported in patients with an X-linked intellectual disability syndrome with an increased risk for congenital anomalies and PHPT. Further research may determine if genetic testing for ZFX could be of potential benefit for patients with PHPT and developmental anomalies, even in the absence of a family history of parathyroid disease.

Opportunities to improve the diagnosis and treatment of primary hyperparathyroidism: retrospective cohort study

Background

Although primary hyperparathyroidism (PHPT) is readily diagnosed biochemically and can be cured with low-risk surgery, it is often underrecognized and undertreated. Our objectives were to characterize, within our health system, how often patients with hypercalcemia were evaluated for PHPT and how often patients with PHPT underwent definitive treatment with parathyroidectomy.

Methods

Ambulatory patients aged 18 years or older seen at our health system between January 2018 and June 2023 with chronic hypercalcemia were identified from the medical record. After excluding causes of secondary hyperparathyroidism, the proportion of patients with parathyroid hormone (PTH) tests was calculated. Among patients with biochemical evidence of PHPT, the proportion of patients who underwent parathyroidectomy was calculated. Multivariable logistic regression was used to identify factors associated with an evaluation for PHPT and, separately, with parathyroidectomy.

Results

Of 7,675 patients with chronic hypercalcemia, 3,323 (43.3%) had a PTH test obtained within 6 months. An age between 40-49 vs. <30 years [(odds ratio (OR) =3.2; 95% confidence interval (CI): 1.8-5.6; P<0.001], a serum calcium level between 11.6-12.0 vs. <11.0 mg/dL (OR =3.9; 95% CI: 3.2-4.7; P<0.001), and osteoporosis (OR =3.1; 95% CI: 2.7-3.5; P<0.001) were associated with an evaluation for PHPT. Among those with PTH levels, 1,327 (39.9%) had PHPT but only 916 (69.0%) were recognized. Three hundred and forty-five (26.0%) patients with PHPT underwent parathyroidectomy. An increasing number of surgical indications was associated with parathyroidectomy (P<0.001), though overall rates remained less than 40%. Among indications for surgery, including age and serum total calcium level, only osteoporosis was associated with parathyroidectomy (OR =2.0; 95% CI: 1.4-2.8; P<0.001).

Conclusions

In this study, more than half of patients with chronic hypercalcemia were not evaluated for PHPT. Among patients with biochemical evidence of PHPT, one-third were unrecognized and only one-in-four received curative treatment. Opportunities to improve the management of PHPT exist within our large integrated health system.

TRPC3 Is Downregulated in Primary Hyperparathyroidism

Transient receptor potential canonical sub-family channel 3 (TRPC3) is considered to play a critical role in calcium homeostasis. However, there are no established findings in this respect with regard to TRPC6. Although the parathyroid gland is a crucial organ in calcium household regulation, little is known about the protein distribution of TRPC channels-especially TRPC3 and TRPC6-in this organ. Our aim was therefore to investigate the protein expression profile of TRPC3 and TRPC6 in healthy and diseased human parathyroid glands. Surgery samples from patients with healthy parathyroid glands and from patients suffering from primary hyperparathyroidism (pHPT) were investigated by immunohistochemistry using knockout-validated antibodies against TRPC3 and TRPC6. A software-based analysis similar to an H-score was performed. For the first time, to our knowledge, TRPC3 and TRPC6 protein expression is described here in the parathyroid glands. It is found in both chief and oxyphilic cells. Furthermore, the TRPC3 staining score in diseased tissue (pHPT) was statistically significantly lower than that in healthy tissue. In conclusion, TRPC3 and TRPC6 proteins are expressed in the human parathyroid gland. Furthermore, there is strong evidence indicating that TRPC3 plays a role in pHPT and subsequently in parathyroid hormone secretion regulation. These findings ultimately require further research in order to not only confirm our results but also to further investigate the relevance of these channels and, in particular, that of TRPC3 in the aforementioned physiological functions and pathophysiological conditions.

Patient-reported outcome measures for primary hyperparathyroidism: a systematic review of measurement properties

BACKGROUND

The quality of patient-reported outcome measures (PROMs) used to assess the outcomes of primary hyperparathyroidism (PHPT), a common endocrine disorder that can negatively affect patients' health-related quality of life due to chronic symptoms, has not been rigorously examined. This systematic review aimed to summarize and evaluate evidence on the measurement properties of PROMs used in adult patients with PHPT, and to provide recommendations for appropriate measure selection.

METHODS

After PROSPERO registration (CRD42023438287), Medline, EMBASE, CINAHL Complete, Web of Science, PsycINFO, and Cochrane Trials were searched for full-text articles in English investigating PROM development, pilot studies, or evaluation of at least one PROM measurement property in adult patients with any clinical form of PHPT. Two reviewers independently identified studies for inclusion and conducted the review following the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) Methodology to assess risk of bias, evaluate the quality of measurement properties, and grade the certainty of evidence.

RESULTS

From 4989 records, nine PROM development or validation studies were identified for three PROMs: the SF-36, PAS, and PHPQoL. Though the PAS demonstrated sufficient test-retest reliability and convergent validity, and the PHPQoL sufficient test-retest reliability, convergent validity, and responsiveness, the certainty of evidence was low-to-very low due to risk of bias. All three PROMs lacked sufficient evidence for content validity in patients with PHPT.

CONCLUSIONS

Based upon the available evidence, the SF-36, PAS, and PHPQoL cannot currently be recommended for use in research or clinical care, raising important questions about the conclusions of studies using these PROMs. Further validation studies or the development of more relevant PROMs with strong measurement properties for this patient population are needed.

Molecular Genetic Aspects of Sporadic Multiglandular Primary Hyperparathyroidism

Multiglandular primary hyperparathyroidism (MGD) represents a rare form of primary hyperparathyroidism (PHPT). MGD is associated with hereditary PHPT, but the sporadic MGD is more common and affects a similar patient profile as single gland parathyroid disease (SGD). The distinction between SGD and MGD is of great clinical importance, especially for the strategy of parathyroidectomy. Based on the limited knowledge available, MGD is likely to be a genetically heterogeneous disease resulting from the interaction of germline and somatic DNA mutations together with epigenetic alterations. Furthermore, these events may combine and occur independently in parathyroid tumors within the same individual with MGD. Gene expression profiling has shown that SGD and MGD may represent distinct entities in parathyroid tumorigenesis. We are waiting for studies to analyze exactly which genes are different in SGD and MGD in order to identify potential biomarkers that can distinguish between the two forms of the disease.

A Knock-In Mouse Model of the Gcm2 Variant p.Y392S Develops Normal Parathyroid Glands

Context

The glial cells missing 2 (GCM2) gene functions as a transcription factor that is essential for parathyroid gland development, and variants in this gene have been associated with 2 parathyroid diseases: isolated hypoparathyroidism in patients with homozygous germline inactivating variants and primary hyperparathyroidism in patients with heterozygous germline activating variants. A recurrent germline activating missense variant of GCM2, p.Y394S, has been reported in patients with familial primary hyperparathyroidism.

Objective

To determine whether the GCM2 p.Y394S missense variant causes overactive and enlarged parathyroid glands in a mouse model.

Methods

CRISPR/Cas9 gene editing technology was used to generate a mouse model with the germline heterozygous Gcm2 variant p.Y392S that corresponds to the human GCM2 p.Y394S variant. Wild-type (Gcm2+/+) and germline heterozygous (Gcm2+/Y392S) mice were evaluated for serum biochemistry and parathyroid gland morphology.

Results

Gcm2 +/Y392S mice did not show any change compared to Gcm2+/+ mice in serum calcium and parathyroid hormone levels, parathyroid gland histology, cell proliferation, or parathyroid gland size.

Conclusion

The mouse model of the p.Y392S variant of Gcm2 shows that this variant is tolerated in mice, as it does not increase parathyroid gland cell proliferation and circulating calcium or PTH levels. Further investigation of Gcm2+/Y392S mice to study the effect of this variant of Gcm2 on early events in parathyroid gland development will be of interest.

Genetic testing for familial hyperparathyroidism: clinical-genetic profile in a Mediterranean cohort

Background

Approximately 10% of primary hyperparathyroidism cases are hereditary, due to germline mutations in certain genes. Although clinically relevant, a systematized genetic diagnosis is missing due to a lack of firm evidence regarding individuals to test and which genes to evaluate.

Methods

A customized gene panel (AIP, AP2S1, CASR, CDC73, CDKN1A, CDKN1B, CDKN2B, CDKN2C, GCM2, GNA11, MEN1, PTH, RET, and TRPV6) was performed in 40 patients from the Mediterranean area with suspected familial hyperparathyroidism (≤45 years of age, family history, high-risk histology, associated tumour, multiglandular disease, or recurrent hyperparathyroidism). We aimed to determine the prevalence of germline variants in these patients, to clinically characterize the probands and their relatives, and to compare disease severity in carriers versus those with a negative genetic test.

Results

Germline variants were observed in 9/40 patients (22.5%): 2 previously unknown pathogenic/likely pathogenic variants of CDKN1B (related to MEN4), 1 novel variant of uncertain significance of CDKN2C, 4 variants of CASR (3 pathogenic/likely pathogenic variants and 1 variant of uncertain significance), and 2 novel variants of uncertain significance of TRPV6. Familial segregation studies allowed diagnosis and early treatment of PHPT in first-degree relatives of probands.

Conclusion

The observed prevalence of germline variants in the Mediterranean cohort under study was remarkable and slightly higher than that seen in other populations. Genetic screening for suspected familial hyperparathyroidism allows the early diagnosis and treatment of PHPT and other related comorbidities. We recommend genetic testing for patients with primary hyperparathyroidism who present with high-risk features.