Update on genetic and clinical aspects of primary hyperparathyroidism

Excessive proliferation and apoptosis of parathyroid cells contribute to primary hyperparathyroidism in rabbit model

To explore the molecular pathogenesis of primary hyperparathyroidism (PHPT), we investigated the proliferation and apoptosis of parathyroid cells in a rabbit model of diet-induced PHPT. A total of 120 adult Chinese rabbits were randomly divided into normal diet (Ca:P, 1:0.7) group (control group) or a high-phosphate diet (Ca:P, 1:7) group (experimental group). The thyroid and parathyroid complexes were harvested for 1-month interval from month 1 to month 6. The expression of proliferation markers, including proliferating cell nuclear antigen (PCNA) and cyclin-D1, and B cell lymphoma-2 (Bcl-2), were evaluated by immunohistochemistry in thyroid and parathyroid tissues. Apoptosis was quantified by DNA-fragment terminal labeling. Our results demonstrated that parathyroid cells in the experimental group started proliferating from the end of the 2nd month, the expression of PCNA, Bcl-2, and cyclin-D1 were significantly higher in the PHPT group than those of the control group (p<0.05). Furthermore, the apoptosis index (AI) was positively correlated with the glandular cell count and expression of PCNA in the 6th month in the PHPT group. Overall, our results suggested that excessive proliferation and apoptosis of parathyroid cells may contribute to the pathogenesis of PHPT through PCNA-related, Bcl-2-related, and cyclin-D1-related pathways.

Primary Hyperparathyroidism in the Common Orthopaedic Practice

An extensive review of the publications on primary hyperparathyroidism (pHPT) is presented in this report. It has strongly been emphasized in the literature that patients with pHPT may present either with the classical symptomatology or with asymptomatic disease, emerged due to biochemical screening. The clinical and epidemiological presentation of pHPT in western countries has changed profoundly during the past few decades, and bone disease is nowadays a distinct rarity. The introduction of serum calcium screening for osteoporosis and the technological advances in the laboratory assessment of parathyroid hormone have played important roles in early diagnosis. Subsequently, the disease is increasingly being detected as asymptomatic hypercalcaemia without guiding signs or symptoms. A third type of disease, the normocalcaemic variant, has been recently described in the literature. However, the potential diagnosis of pHPT should always be on the orthopaedics’ list of differential diagnoses in female or elderly patients with vertebral fractures and nephrolithiasis, either symptomatic or asymptomatic, as well as when solitary or multiple osteolytic lesions are encountered on the radiographs.

Additionally, a middle aged woman with parathyroid adenoma and subsequent brown tumors detected on the pelvic radiographs is reported. Her initial laboratory findings indicated a minimal increase of the serum calcium, a mild increase of the erythrocyte sedimentation rate, and a significant increase in total serum alkaline phosphatase. Finally, the detection of elevated parathyroid hormone levels indicated the diagnosis of pHPT and necessitated imaging studies of the parathyroid glands, which indicated a parathyroid adenoma. Following successful excision of the parathyroid adenoma, the patient suffered from the hungry bone syndrome. After a follow-up of 20 years, the patient had normal calcium, vitamin D, and parathyroid hormone serum levels, while a pelvic radiograph indicated no significant changes in the appearance of the brown tumors.

Primary Hyperparathyroidism in the Common Orthopaedic Practice

An extensive review of the publications on primary hyperparathyroidism (pHPT) is presented in this report. It has strongly been emphasized in the literature that patients with pHPT may present either with the classical symptomatology or with asymptomatic disease, emerged due to biochemical screening. The clinical and epidemiological presentation of pHPT in western countries has changed profoundly during the past few decades, and bone disease is nowadays a distinct rarity. The introduction of serum calcium screening for osteoporosis and the technological advances in the laboratory assessment of parathyroid hormone have played important roles in early diagnosis. Subsequently, the disease is increasingly being detected as asymptomatic hypercalcaemia without guiding signs or symptoms. A third type of disease, the normocalcaemic variant, has been recently described in the literature. However, the potential diagnosis of pHPT should always be on the orthopaedics’ list of differential diagnoses in female or elderly patients with vertebral fractures and nephrolithiasis, either symptomatic or asymptomatic, as well as when solitary or multiple osteolytic lesions are encountered on the radiographs.

Additionally, a middle aged woman with parathyroid adenoma and subsequent brown tumors detected on the pelvic radiographs is reported. Her initial laboratory findings indicated a minimal increase of the serum calcium, a mild increase of the erythrocyte sedimentation rate, and a significant increase in total serum alkaline phosphatase. Finally, the detection of elevated parathyroid hormone levels indicated the diagnosis of pHPT and necessitated imaging studies of the parathyroid glands, which indicated a parathyroid adenoma. Following successful excision of the parathyroid adenoma, the patient suffered from the hungry bone syndrome. After a follow-up of 20 years, the patient had normal calcium, vitamin D, and parathyroid hormone serum levels, while a pelvic radiograph indicated no significant changes in the appearance of the brown tumors.

Proteomics Analysis of Tissue Samples Reveals Changes in Mitochondrial Protein Levels in Parathyroid Hyperplasia over Adenoma

BACKGROUND/AIM

To unveil the pathophysiology of primary hyperparathyroidism, molecular details of parathyroid hyperplasia and adenoma have to be revealed. Such details will provide the tools necessary for differentiation of these two look-alike diseases. Therefore, in the present study, a comparative proteomic study using postoperative tissue samples from the parathyroid adenoma and parathyroid hyperplasia patients was performed.

MATERIALS AND METHODS

Protein extracts were prepared from tissue samples (n=8 per group). Protein pools were created for each group and subjected to DIGE and conventional 2DE. Following image analysis, spots representing the differentially regulated proteins were excised from the and used for identification via MALDI-TOF/TOF analysis.

RESULTS

The identities of 40 differentially-expressed proteins were revealed. Fourteen of these proteins were over-expressed in the hyperplasia while 26 of them were over-expressed in the adenoma.

CONCLUSION

Most proteins found to be over-expressed in the hyperplasia samples were mitochondrial, underlying the importance of the mitochondrial activity as a potential biomarker for differentiation of parathyroid hyperplasia from adenoma.

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.

Genetic basis of familial isolated hyperparathyroidism: a case series and a narrative review of the literature

Primary hyperparathyroidism is a heterogeneous clinical entity. In the clinical setting, the diagnosis and management of familial isolated hyperparathyroidism (FIHP) and other familial hyperparathyroidism (FHPT) forms continue to rely on clinical, laboratory, and histological findings, with careful examination of the family. In this article, we report a case series of FIHP in a four-generation Greek family, with no identifiable gene mutations. Clinical approach and long-term follow-up are discussed and a narrative review of the genetic basis of this entity has been performed.

Calcium intake and risk of primary hyperparathyroidism in women: prospective cohort study

OBJECTIVE

To examine the association between calcium intake and risk of primary hyperparathyroidism in women.

DESIGN

Prospective cohort study.

SETTING

Nurses' Health Study I, which originally recruited participants from the 11 most populous states in the United States.

PARTICIPANTS

58,354 female registered nurses enrolled in the Nurses' Health Study I aged 39-66 years in 1986 and with no history of primary hyperparathyroidism. Calcium intake was assessed every four years using semiquantitative questionnaires on food frequency.

MAIN OUTCOME MEASURE

Incident primary hyperparathyroidism, confirmed by medical record review.

RESULTS

During 22 years of follow-up, we recorded 277 incident cases of primary hyperparathyroidism. Women were divided into five equal groups, according to intake of dietary calcium. After adjusting for age, body mass index, race, and other factors, the relative risk of primary hyperparathyroidism for women in the group with the highest intake of dietary calcium was 0.56 (95% confidence interval 0.37 to 0.86, P=0.009 for trend), compared with the group with the lowest intake. The multivariable relative risk of primary hyperparathyroidism for women taking more than 500 mg/day of calcium supplements compared with no calcium supplements was 0.41 (95% confidence interval 0.29 to 0.60, P<0.001 for trend). Analyses restricted to participants with regular physical exams did not significantly change the association between calcium intake and risk of primary hyperparathyroidism.

CONCLUSION

Increased calcium intake is independently associated with a reduced risk of primary hyperparathyroidism in women.

Familial hypocalciuric hypercalcaemia: a review

PURPOSE OF REVIEW

Hypercalcaemia is a potentially life-threatening condition. Familial hypocalciuric hypercalcaemia (FHH) is a rare, lifelong, benign condition. It is important to separate this condition from other hypercalcaemic states such as hypercalcaemia of malignancy and primary hyperparathyroidism (PHPT).

RECENT FINDINGS

FHH is caused by inactivating mutations in the calcium sensing receptor (CASR) gene leading to a general calcium-hyposensitivity, compensatory hypercalcaemia and hypocalciuria. The inheritance of FHH is autosomal dominant. Similar to PHPT, FHH is characterized by hypercalcaemia, unsuppressed or elevated plasma parathyroid hormone, and typically normal renal function. The phenotype is normal, and hypercalcaemic symptoms are generally absent. The hallmark is a relatively low urine calcium excretion in contrast to PHPT, in which urine calcium excretion is increased. The vitamin D status as measured by plasma 25-hydroxyvitamin D has been reported to be normal with normal seasonal variations, whereas plasma 1,25-dihydroxyvitamin D has been found slightly increased compared to normal. Bone mineral density Z-scores are normal in spite of a slightly increased bone turnover. Differential diagnoses include mainly PHPT, but in some cases also hypercalcaemia of malignancy and use of thiazide diuretics.

SUMMARY

In general, FHH does not require treatment. We recommend a two-step diagnostic procedure. First, the calcium/creatinine clearance ratio is measured from a 24-h urine. Second, all patients with calcium/creatinine clearance ratio of 0.020 or less are tested for mutations in the CASR gene. The diagnostic sensitivity of this setup is 98%.

Molecular alterations in sporadic primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a frequent endocrine disorder characterized by an excessive autonomous production and release of parathyroid hormone (PTH) by the parathyroid glands. This endocrinopathy may result from the development of a benign lesion (adenoma or hyperplasia) or from a carcinoma. Most of the PHPT cases occur sporadically; however, approximately 10% of the patients present a familial form of the disease. The molecular mechanisms underlying the pathogenesis of sporadic PHPT are incompletely understood, even though somatic alterations in MEN1 gene and CCND1 protein overexpression are frequently observed. The MEN1 gene is mutated in about 30% of the parathyroid tumours and the protooncogene CCND1 is implicated in parathyroid neoplasia by rearrangements, leading to an overexpression of CCND1 protein in parathyroid cells. The aim of this work is to briefly update the molecular alterations underlying sporadic primary hyperparathyroidism.

HRPT2-related familial isolated hyperparathyroidism: could molecular studies direct the surgical approach?

It is still debatable which is the best management to familial forms of hyperparathyroidism. Conservative, minimally invasive or aggressive surgical approaches have been proposed from different groups around the world. Our objective was to study the gene mutation, expression of HRPT2 and the clinical outcome after 32 years of follow-up in one Brazilian kindred with familial isolated hyperparathyroidism (FIHP). Clinical and biochemical data, direct sequencing of the HRPT2 gene, analysis of parafibromin expression using RT-PCR, and immunohistochemistry were done. A nonsense mutation was found in exon 1 (c.96G>A)(p.Trp32X) in all affected members studied. Using RT-PCR, mRNA transcription was altered with complete absence of both transcripts in tumor tissue. Immunohistochemical analysis of tumors showed loss of parafibromin immunoreactivity. In this kindred there was a high prevalence of recurrence (75%), or persistence after less than subtotal parathyroidectomy that led us to consider a more aggressive surgical approach should be discussed among the affected family members, once surgical criteria was met. We concluded that it is necessary to individualize the surgical approach for HRPT2-related hyperparathyroidism until we can gather a better phenotype-genotype correlation in larger series, to best define their treatment.

Primary hyperparathyroidism and the skeleton

Today, primary hyperparathyroidism (PHPT) in the developed countries is typically a disease with few or no obvious clinical symptoms. However, even in the asymptomatic cases the endogenous excess of PTH increases bone turnover leading to an insidious reversible loss of cortical and trabecular bone because of an expansion of the remodelling space and an irreversible loss of cortical bone due to increased endocortical resorption. In contrast trabecular bone structure and integrity to a large extent is maintained and there may be a slight periosteal expansion. Most studies have reported decreased bone mineral density (BMD) in PHPT mainly located at cortical sites, whereas sites rich in trabecular bone only show a modest reduction or even a slight increase in BMD. The frequent occurrence of vitamin D insufficiency and deficiency in PHPT and increased plasma FGF23 levels may also contribute to the decrease in BMD. The effect of smoking is unsolved. Epidemiological studies have shown that the relative risk of spine and nonspine fractures is increased in untreated PHPT starting up to 10 years before the diagnosis is made. Successful surgery for PHPT normalizes bone turnover, increases BMD and decreases fracture risk based on larger epidemiological studies. However, 10 years after surgery fracture risk appears to increase again due to an increase in forearm fractures. There are no randomized controlled studies (RCTs) demonstrating a protective effect of medical treatment on fracture risk in PHPT. Less conclusive studies suggest that vitamin D supplementation may have a beneficial effect on plasma PTH and BMD in vitamin D deficient PHPT patients. Hormone replacement therapy (HRT) and maybe SERM appear to reduce bone turnover and increase BMD. However, their nonskeletal side-effects preclude their use for this purpose. Bisphosphonates reduce bone turnover and increase BMD in PHPT as in osteoporosis and may be a therapeutical option in selected patients with low BMD. Obviously, there is a need for larger RCTs with fractures as end-points that appraise this possibility. Calcimimetics reduce plasma calcium and PTH in PHPT but has no beneficial effect on bone turnover or BMD. In symptomatic hypercalcaemic PHPT with low BMD where curative surgery is impossible or contraindicated a combination of a calcimimetic and a bisphosphonate may be an undocumented therapeutical option that needs further evaluation.

Corpus callosum aplasia in a young patient with a parathyroid adenoma

A young man with primary hyperparathyroidism due to a parathyroid adenoma and aplasia of the corpus callosum is presented. We hypothesize a possible genetic association of the two pathologies: a proportion of the sporadic parathyroid adenomas are associated with genetic abnormalities of chromosome 11 and in some cases of corpus callosum aplasia, aneuploidy or polyploidy of this chromosome has been described.

Analysis of the diagnostic presentation profile, parathyroidectomy indication and bone mineral density follow-up of Brazilian patients with primary hyperparathyroidism

Primary hyperparathyroidism is an endocrine disorder with variable clinical expression, frequently presenting as asymptomatic hypercalcemia in Western countries but still predominantly as a symptomatic disease in developing countries. The objective of this retrospective study was to describe the diagnostic presentation profile, parathyroidectomy indication and post-surgical bone mineral density follow-up of patients with primary hyperparathyroidism seen at a university hospital. We found 115 patients (92 women, median age 56 years) with primary hyperparathyroidism diagnosed during the last 20 years. We defined symptomatic patients based on the presence of any classical symptom affecting bone, kidney or the neuromuscular system. Surgical criteria followed the guidelines of the National Institutes of Health regarding asymptomatic primary hyperparathyroidism. Symptomatic patients and patients meeting surgical criteria for parathyroidectomy were 66 and 93% of the sample, respectively. Median calcium and parathyroid hormone values were 11.9 mg/dL and 189 pg/mL, respectively. After surgical treatment, 97% of patients were cured, with increases in bone mineral density of 19.4% in the lumbar spine and 15.7% in the femoral neck 3 years after surgery. Greater bone mass increases were detected in pre-menopausal women, men, and in symptomatic and younger patients, both in the lumbar spine and femoral neck. Our results support the previous findings of a predominantly symptomatic disease with a presentation profile that could be mainly related to a delayed diagnosis. Nevertheless, genetic and racial backgrounds, and nutritional factors such as calcium and vitamin D deficiency may play a role in the clinical presentation of primary hyperparathyroidism of Brazilian patients.

A vacuolar ATPase inhibitor, FR167356, prevents bone resorption in ovariectomized rats with high potency and specificity: potential for clinical application

FR167356, a novel inhibitor of vacuolar ATPase, has high potency against osteoclast V-ATPase and low potency against lysosomal V-ATPase. FR167356 is the first compound of this nature to be tested. It has the potential to be useful for clinical application.

INTRODUCTION

It has been suggested that the key issue regarding the therapeutic usefulness of V-ATPase inhibitors is their selectivity.

MATERIALS AND METHODS

In in vitro and in vivo studies, we compared FR167356 with other vacuolar ATPase (V-ATPase) inhibitors, bafilomycin A1 and SB242784. H+ transport by various membrane vesicles was assayed by measuring uptake of acridine orange. Inhibitory activity against in vitro bone resorption was examined by measuring the Ca2+ release from cultured calvariae. In vivo, hypercalcemia was induced by retinoic acid in thyroparathyroidectomized-ovariectomized rats, and the effect on serum Ca2+ level was assessed. Ovariectomized rats were treated with FR167356 or SB242784. One week after surgery, free deoxypyridinoline levels in 24-h urine samples, which were collected from 6 h after administration of FR167356, were measured by ELISA. After 4 weeks of treatment, plasma biochemical parameters were analyzed. BMD of the distal femur metaphysis was measured with pQCT. Histomorphometric analysis of the proximal tibias was performed. Blood gases of rats treated with FR167356 were measured with a blood gas analyzer for estimating the effect of FR167356 on in vivo function of renal V-ATPase.

RESULTS

FR167356, which is distinctly different from other V-ATPase inhibitors, has a high potency against osteoclast V-ATPase and low potency against lysosomal V-ATPase. Similarly, FR167356 inhibited bone resorption in vitro when stimulated by PTH, IL-1, and IL-6. FR167356 reduced retinoic acid-induced hypercalcemia in thyroparathyroidectomized-ovariectomized rats in a dose-dependent manner. Moreover, FR167356 was shown to restore BMD of ovariectomized rats caused by the inhibition of bone resorption. Ovariectomized rats treated with FR167356 did not show adverse symptoms, whereas SB242784 caused a decrease in body weight gain and significant changes in two plasma biochemical parameters. Interestingly, FR167356 treatment did not affect blood acid-base balance; however, FR167356 inhibited renal V-ATPase with a similar potency as for osteoclast V-ATPase inhibition.

CONCLUSION

Comparison of FR167356 with SB242784 implies that the characteristics of FR167356 may be more appropriate for clinical application as a V-ATPase inhibitor.

Vitamin D repletion in patients with primary hyperparathyroidism and coexistent vitamin D insufficiency

Vitamin D insufficiency is common in patients with primary hyperparathyroidism (PHPT) and may be associated with more severe and progressive disease. Uncertainty exists, however, as to whether repletion of vitamin D should be undertaken in patients with PHPT. Here we report the effects of vitamin D repletion on biochemical outcomes over 1 yr in a group of 21 patients with mild PHPT [serum calcium <12 mg/dl (3 mmol/liter)] and coexistent vitamin D insufficiency [serum 25 hydroxyvitamin D [25(OH)D] <20 microg/liter (50 nmol/liter)]. In response to vitamin D repletion to a serum 25(OH)D level greater than 20 microg/liter (50 nmol/liter), mean levels of serum calcium and phosphate did not change, and serum calcium did not exceed 12 mg/dl (3 mmol/liter) in any patient. Levels of intact PTH fell by 24% at 6 months (P < 0.01) and 26% at 12 months (P < 0.01). There was an inverse relationship between the change in serum 25(OH)D and that in intact PTH (r = -0.43, P = 0.056). At 12 months, total serum alkaline phosphatase was significantly lower, and urine N-telopeptides tended to be lower than baseline values (P = 0.02 and 0.13, respectively). In two patients, 24-h urinary calcium excretion rose to exceed 400 mg/d, but the group mean 24-h urinary calcium excretion did not change. These preliminary data suggest that vitamin D repletion in patients with PHPT does not exacerbate hypercalcemia and may decrease levels of PTH and bone turnover. Some patients with PHPT may experience an increase in urinary calcium excretion after vitamin D repletion.

Gland size is associated with changes in gene expression profiles in sporadic parathyroid adenomas

BACKGROUND

Sporadic parathyroid adenomas (SPAs) are benign neoplasms responsible for most cases of primary hyperparathyroidism (pHPT). The molecular pathways responsible for the variations in clinical severity of pHPT are unknown. We studied gene expression profiles in patients with SPAs and pHPT to determine associations between these changes and clinical parameters.

METHODS

We selected 10 patients with solitary SPAs and nonfamilial, non-MEN1 pHPT treated with surgery from 2001 to 2003. Pathologic and clinical data were reviewed. At operation, tissues from SPAs were frozen in liquid nitrogen; total RNA was obtained from sections, and the diagnosis was confirmed with hematoxylin and eosin staining. Control normal parathyroid RNA was age- and sex-matched. RNA was amplified, labeled, and hybridized to a microarray of 22,272 human oligonucleotides. Cluster analysis of gene expression, analysis of expression ratios, and comparison of clinical parameters were performed.

RESULTS

All patients were cured; all specimens were consistent with SPAs. K means clustering divided the 10 patients into 2 distinct 5-patient gene expression groups by using uncentered correlation based on gene subgrouping. Of the clinical parameters, only the mean gland volume was significantly different between group 1 (390 +/- 160 mm(3)) and group 2 (1080 +/- 615 mm(3); P = .032 by Mann-Whitney test). Seventy-five genes were significantly upregulated or downregulated (with a ratio of <.33 or >3) compared with controls. These genes included the v-fos viral oncogene homolog and six calcium ion-binding signaling proteins.

CONCLUSIONS

Differential expression of a few critical genes may contribute to differences in gland volume in SPAs. A better understanding of these pathways may help to define the pathophysiology of pHPT.

The effect of vitamin D status on the severity of bone disease and on the other features of primary hyperparathyroidism (pHPT) in a vitamin D deficient region

A clear relationship between vitamin D status and the clinical indices of primary hyperparathyroidism (pHPT) severity has not been convincingly established. We proposed that such a relationship might exist, in so far as vitamin D deficiency could contribute to the severity of metabolic bone disease and promote the growth of the parathyroid tumor. Accordingly, we undertook a retrospective study and analyzed the clinical, biochemical, radiological and histopathological findings in a group of 49 patients who underwent parathyroidectomy at our center. Patients who had skeletal X-rays were grouped, according to their X-ray findings, in group A (19 patients; 45%) if they had severe bone changes, or group B (23 patients; 55%) if they had mild or no bone changes. Patients were also stratified according to their 25-hydroxyvitamin D (25-OHD) levels in tertiles. The 2 groups were compared using Fisher's exact test or analysis of variance as appropriate. Group A patients were younger (p=0.001), had more musculoskeletal symptoms (p=0.0003), and complained more frequently of fatigue (p=0.02). They had higher alkaline phosphatase (AP; p=0.0002), PTH index (p=0.0007), and serum Ca level (p=0.006). There were more patients from the lower and middle vitamin D tertiles and fewer patients from the upper vitamin D tertile in group A (p=0.02). Post-operative severe hypo-calcemia was more prevalent in group A patients (p<0.0001). Resected parathyroid tumors were larger in size in group A patients (p=0.01), and weighed more (p=0.01). There was a positive correlation between the weight of the parathyroid tumor and the PTH index (p=0.002), and AP level (p=0.0007). We concluded that vitamin D deficiency is a contributing factor to both the severity of bone disease and the high activity of parathyroid tumors seen in many patients with pHPT in vitamin D deficient regions.

Hyperparathyroidism and multiple endocrine neoplasia

Multiple endocrine neoplasia (MEN) syndromes comprise the group of heritable endocrinopathies, MEN 1, MEN 2A, and MEN 2B. Primary hyperparathyroidism caused by multiglandular involvement is usually the initial manifestation in MEN 1, occurring in more than 90% of patients. In patients with MEN 2A, hyperparathyroidism develops less commonly and is usually milder than in MEN 1. Advances in genetics and molecular biology aid in confirming the diagnosis and screening relatives who are carriers or at risk for the disease. Surgery plays an important role in the management of hyperparathyroidism in both MEN 1 and MEN 2A,although the timing and extent of surgery are areas of controversy.Long-term follow-up reveals a high rate of recurrent hyperparathyroidism in MEN 1 despite surgical intervention.