A coordinated cross-disciplinary research initiative to address an increased incidence of narcolepsy following the 2009-2010 Pandemrix vaccination programme in Sweden.

In response to the 2009-2010 influenza A(H1N1)pdm09 pandemic, a mass vaccination programme with the AS03-adjuvanted influenza A(H1N1) vaccine Pandemrix was initiated in Sweden. Unexpectedly, there were a number of narcolepsy cases amongst vaccinated children and adolescents reported. In this review, we summarize the results of a joint cross-disciplinary national research effort to investigate the adverse reaction signal from the spontaneous reporting system and to better understand possible causative mechanisms. A three- to fourfold increased risk of narcolepsy in vaccinated children and adolescents was verified by epidemiological studies. Of importance, no risk increase was observed for the other neurological and autoimmune diseases studied. Genetic studies confirmed the association with the allele HLA-DQB1*06:02, which is known to be related to sporadic narcolepsy. Furthermore, a number of studies using cellular and molecular experimental models investigated possible links between influenza vaccination and narcolepsy. Serum analysis, using a peptide microarray platform, showed that individuals who received Pandemrix exhibited a different epitope reactivity pattern to neuraminidase and haemagglutinin, as compared to individuals who were infected with H1N1. Patients with narcolepsy were also found to have increased levels of interferon-gamma production in response to streptococcus-associated antigens. The chain of patient-related events and the study results emerging over time were subjected to intense nationwide media attention. The importance of transparent communication and collaboration with patient representatives to maintain public trust in vaccination programmes is also discussed in the review. Organizational challenges due to this unexpected event delayed the initiation of some of the research projects, still the main objectives of this joint, cross-disciplinary research effort were reached, and important insights were acquired for future, similar situations in which a fast and effective task force may be required to evaluate vaccination-related adverse events.

Vitamin D receptor genotypes in primary hyperparathyroidism.

Vitamin D and parathyroid hormone (PTH) constitute the main regulators of systemic calcium homeostasis. As well as its calcaemic effects, active vitamin D3(1,25(OH)2D3) has a direct regulatory role on parathyroid cells. Active vitamin D3 acts via its receptor (VDR), and binding of the ligand-receptor complex to specific promoter regions of the PTH gene inhibits transcription. Active vitamin D3 constitutes a principal regulator of parathyroid cell growth, and polymorphism in the VDR gene has recently been related to bone mineral density and suggested as predisposing to osteoporosis. Impaired effects of active vitamin D3 may contribute to the relatively enhanced secretion and cell proliferation seen in hyperparathyroidism (HPT). Indeed, VDR dysfunction, of essentially unknown character, has been demonstrated in the pathological parathyroid tissue of primary HPT as well as HPT secondary to uraemia. Consistent with the essential role of active vitamin D3 in parathyroid regulation, the VDR gene polymorphism was studied in 90 postmenopausal women with primary hyperparathyroidism. The VDR genotype bb was found in 60.0% of HPT patients and in 33.3% of the postmenopausal female controls (P < 0.001). As the b allele has been linked to decreased transcriptional activity or messenger RNA stability, reduced VDR expression may impede regulatory actions of vitamin D and may contribute to parathyroid tumorigenesis in these patients.

Mutation of the multiple endocrine neoplasia type 1 gene in nonfamilial, malignant tumors of the endocrine pancreas.

Endocrine pancreatic tumors are rare neoplasms that occur sporadically or as part of a multiple endocrine neoplasia type 1 (MEN1) syndrome. Germ-line mutations of the MEN1 gene, located at 11q13, have been demonstrated in MEN1 kindreds, and loss of heterozygosity (LOH) on 11q13 together with somatic MEN1 mutations have been detected in 20% of nonfamilial parathyroid tumors. Here, we examine 11 non-MEN1 malignant tumors of the endocrine pancreas, 9 nonfunctioning tumors, and 2 glucagonomas. LOH of at least one informative locus on 11q13 was found in 70% of the tumors. Three tumors displayed somatic mutations of the MEN1 gene together with LOH on 11q13, whereas the corresponding germ-line DNA was normal. These findings support the hypothesis that MEN1 gene mutations contribute to the tumorigenesis of nonfamilial, malignant endocrine pancreatic tumors.

Expression of platelet-derived growth factor beta-receptors on stromal tissue cells in human carcinoid tumors.

Carcinoid tumors of the midgut type are slowly growing neoplasms which often present clinically and histologically pronounced fibrosis around the tumors. Cryosections from 41 neuroendocrine tumors (31 midgut carcinoid tumors, 8 endocrine pancreatic carcinomas, 1 parathyroid carcinoma, and 1 pheochromocytoma) and 22 nonneuroendocrine carcinomas were examined for the presence of platelet-derived growth factor (PDGF) beta-receptor by immunohistochemistry using the monoclonal antibody PDGFR-B2. Twenty midgut carcinoid tumor tissues (66%) and 4 endocrine pancreatic carcinomas (50%) and the parathyroid carcinoma stained positively with the antibody. In contrast, only 2 nonneuroendocrine tumor tissues (10%) were stained, and the staining in these cases was weak. The immunoreaction in the carcinoid tumors was observed in connective tissue cells adjacent to tumor cell clusters but not in the tumor cells themselves. The degree of positive PDGF beta-receptor expression in the carcinoid tissues seems to correlate positively with the presence of macrophages as determined by the monoclonal antibody anti-Leu-M5, but not with other infiltrated lymphocytes identified with the monoclonal antibody anti-Leu-4, or with anti-HLA-DR antibodies. Stromal cells adjacent to tumor cells, including small capillaries, stained more strongly than the stromal cells which were distant from tumor cell clusters. Furthermore, carcinoid tumor metastases from lymph nodes as well as from liver showed stronger immunoreactivity in the stromal cells with the PDGF beta-receptor antibody than the corresponding primary tumors. Our data suggest that carcinoid tumor cells may directly or indirectly induce expression of PDGF beta-receptor on adjacent stromal cells in the tumor tissue, which may contribute to the fibrosis that is often seen around carcinoid tumors.

Human biodistribution of [111In]diethylenetriaminepentaacetic acid-(DTPA)-D-[Phe1]-octreotide and peroperative detection of endocrine tumors.

Requisites for preoperative and intraoperative tumor localization with [111In]diethylenetriaminepentaacetic acid-D-[Phe1]-octreotide scanning were explored in 23 patients with endocrine tumors (15 carcinoids, 4 insulinomas, and single cases of gastrinoma, medullary thyroid carcinoma, aldosteronoma, and paraganglioma). The patients were subjected to Octreoscan single photon emission computed tomographic examination prior to surgery and well counter investigation of nuclide uptake in tumors and normal tissues sampled at surgery. Somatostatin receptor-positive tumors demonstrated efficient nuclide accumulation with mean tumor:blood radioactivity ratios of 180-370 (for carcinoids and insulinoma), compared with tissue:blood ratios of 302 for spleen, 42 for liver, and < 10-15 in other normal tissues (pancreas, small intestine, and mesenteric fat). Inefficient preoperative visualization of lesions was related to inconspicuous size, as for primary intestinal carcinoids, tiny liver metastases, and a single small insulinoma. High background activity, pronounced tumor fibrosis, and meager accumulation of tracer also interfered with visualization. Tumor deposits in organs with low background activity (such as carcinoid mesenteric metastases and endocrine pancreatic tumors) were generally most readily detected. Intraoperative investigations with hand-held gamma detector probes were disturbed by obvious high background activity. These investigations revealed two preoperatively unrecognized primary intestinal carcinoids, which, however, were both palpable during surgery. These studies, therefore, had little impact on the surgical strategy.

Dimethyl sulfoxide increases cytoplasmic Ca2+ concentration and inhibits parathyroid hormone release in normal bovine and pathological human parathyroid cells.

The acute effects of dimethyl sulfoxide (DMSO) on parathyroid hormone (PTH) release and the cytoplasmic Ca2+ concentration (Ca2+i) were studied in dispersed bovine cells and cells isolated from human parathyroid adenomas. At extracellular Ca2+ concentrations in the 0.5-3.0 mM range, but not at less than 25 nM, addition of 2% DMSO caused a rapid rise of Ca2+i. This effect corresponded to an inhibition of PTH release and there was a strong negative correlation between Ca2+i and secretion. The actions of DMSO on Ca2+i and PTH release were less pronounced in the pathological human cells. The data are consistent with a DMSO effect on the Ca2+-sensor function of the parathyroid cell, possibly mediated by an altered plasma membrane fluidity.

Modulation of the Ca2+-sensing function of parathyroid cells in vitro and in hyperparathyroidism.

When raising the extracellular Ca2+ concentration stepwise from 0.5 to 3.0 mM, bovine parathyroid cells reacted with initial transient and sustained elevations of the cytoplasmic Ca2+ concentration (Ca2+i), as well as more than 50% inhibition of parathyroid hormone (PTH) release. Human parathyroid adenoma cells and bovine cells cultured for 1 day or exposed to a low concentration of a monoclonal antiparathyroid antibody exhibited right-shifted dependencies of PTH release and Ca2+i on extracellular Ca2+ and reduced Ca2+i transients. The protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA) further right-shifted the dose response relationship for Ca2+ regulated Ca2+i of the adenoma cells, whereas the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) tended to normalize it, without affecting Ca2+i of normal bovine cells. In cells from an oxyphil adenoma and a parathyroid carcinoma as well as in bovine cells cultured 4 days or exposed to a high concentration of the antiparathyroid antibody, there were no Ca2+i transients, very small increases in steady-state Ca2+i and nonsuppressible PTH release. The results suggest that reduced availability of a putative Ca2+-receptor and increased protein kinase C activity may be important factors in the decreased Ca2+ sensitivity of abnormal parathyroid cells.

Kinetic evidence for cytoplasmic calcium as an inhibitory messenger in parathyroid hormone release.

A sudden change of extracellular Ca2+ from 0.5 to 3.0 mM resulted in a transient rise of the cytoplasmic Ca2+ concentration (Ca2+i) followed by a sustained increase in parathyroid cells loaded with the Ca2+-indicator fura-2. The initial transient could be eliminated by increasing the Ca2+ buffering capacity of the cytoplasm. Under such conditions the rise of Ca2+i exhibited kinetics reminiscent of those for 45Ca uptake and cell depolarization. Addition of 0.5 mM Mn2+ mimicked the effect of raising the extracellular Ca2+ concentration, since there was an initial Ca2+i transient followed by a slower entry of Mn2+ into the cells. This reaction pattern was different from that of pancreatic alpha 2-cells in which there was no substantial influx of Mn2+ before depolarization with arginine. When measuring the kinetics of parathyroid hormone (PTH) release it was apparent that Ca2+ inhibition of secretion followed Ca2+i and thus became substantially delayed after eliminating the initial transient. The results support the concept of a depolarizing Ca2+ permeability in the parathyroid cell membrane which can be activated by external Ca2+, and indicate that Ca2+i is an inhibitory messenger of importance for the physiological regulation of PTH release.

Paradoxical effects of K+ and D-600 on parathyroid hormone secretion and cytoplasmic Ca2+ in normal bovine and pathological human parathyroid cells.

The effects of K+ and the Ca2+ channel blocker D-600 on parathyroid hormone (PTH) release and cytoplasmic Ca2+ activity (Ca2+i) were measured at different Ca2+ concentrations in dispersed parathyroid cells from normal cattle and from patients with hyperparathyroidism. When the extracellular Ca2+ concentration was raised within the 0.5-3.0 mM range Ca2+i increased and PTH secretion was inhibited. There was also a stimulatory effect of Ca2+ on secretion as indicated by a parallel decrease of Ca2+i and PTH release when extracellular Ca2+ was reduced to less than 25 nM. Addition of 30-50 mM K+ stimulated PTH release and lowered Ca2+i. The effect of K+ was less pronounced in the human cells with a decreased suppressability of PTH release. The Ca2+ channel blocker D-600 had no effect on Ca2+i and PTH release in the absence of extracellular Ca2+. However, at 0.5-1.0 mM Ca2+, D-600 increased Ca2+i and inhibited PTH release, whereas the opposite effects were obtained at 3.0 mM Ca2+. The transition from inhibition to stimulation occurred at a higher Ca2+ concentration in the human cells and the right-shift in the dose-effect relationship for Ca2+-inhibited PTH release tended to be normalized by D-600. It is suggested that K+ stimulates PTH release by increasing the intracellular sequestration of Ca2+ and that the reduced response in the parathyroid human cells is due to the fact that Ca2+i already is lowered. D-600 appears to have both Ca2+ agonistic and antagonistic actions in facilitating and inhibiting Ca2+ influx into the parathyroid cells at low and high concentrations of extracellular Ca2+, respectively. D-600 and related drugs are considered potentially important for the treatment of hyperparathyroidism.

Graves' disease with moderate-severe endocrine ophthalmopathy-long term results of a prospective, randomized study of total or subtotal thyroid resection.

The optimal thyroid surgery to be performed in patients with Graves' disease and concomitant endocrine ophthalmopathy is a matter of debate. We randomly assigned 44 patients with moderate-severe eye signs in a trial of treatment with subtotal, leaving a small (approximately 2 g) thyroid remnant, or total thyroidectomy. At inclusion, the patients had been treated with antithyroid drugs, and corticosteroids been given to 12 (27%). All received postoperative thyroxine supplementation and were followed for 3 years at regular examinations. The eye disease improved in all cases, and throughout the study, the two groups did not differ with regard to subjective and objective eye symptoms and laboratory findings. At the study start, motility disturbances were present in 8 and 11 of the cases in the subtotal and total resection group and proptosis in 16 and 17, respectively. After 3 years, the corresponding data were 3 and 6 cases with motility defects and 16 and 15 cases with proptosis. Thyrotropin (TSH)-receptor antibody levels gradually fell and became nondetectable in 21 (49%). The surgical complication rate (permanent recurrent laryngeal nerve paresis and permanent hypoparathyroidism) was significantly higher in the total thyroidectomy group. The data indicate that in patients with Graves' disease and active endocrine ophthalmopathy, subtotal thyroidectomy, leaving a small thyroid remnant, will reduce the risk of surgical complications but not the beneficial effect of surgery.

Longitudinal studies of mild primary hyperparathyroidism.

In 1969, a health survey was offered to all inhabitants of a town district in Sweden. A clinical examination was carried out, and among other variables, a measurement was made of serum calcium. The same procedure was repeated in 1971. From these two investigations a cohort of 176 individuals (1.1%) with sustained hypercalcemia was identified who could be followed during the subsequent 15 years. Comparisons were made with an age- and sex-matched control group from the same health survey. Survival was significantly lower in the hypercalcemic cohort than in the control group. This reduction was related to the degree of hypercalcemia and apparently mainly due to diseases of the circulatory organs. There was no marked deterioration of renal function, and although there was in some patients a moderate progression of the hypercalcemia, none developed a hypercalcemic crisis during 15 years of follow-up. In consecutively referred patients with primary hyperparathyroidism, psychiatric disturbances of mainly a depressive character were found upon detailed analysis within a majority of the patients, and parathyroid surgery resulted in a clear improvement in mental health.

Interaction of monoclonal antiparathyroid antibody with Ca2+ agonistic actions of Mn2+ in normal human parathyroid cells.

Effects of the monoclonal antiparathyroid antibodies G11 and E11 on Mn2+ interaction with individual normal human parathyroid cells were studied. At 0.5mM Ca2+, 3mM Mn2+ induced a rapid transient increase in cytoplasmic Ca2+ [Ca2+i] followed by quenching of the fluorescence from the Ca2+ indicator fura-2 as Mn2+ entered into the cells. Whereas the antibody E11 had no effects, treatment with G11 abolished the Ca2+i transient and considerably delayed the entry of Mn2+. The results support the presence of a cation-sensitive receptor mechanism on parathyroid cells and indicate that the antibody G11 not only blocks the interaction between Ca2+ and this receptor mechanism but also that of Mn2+.

Hyperparathyroidism is associated with reduced expression of a parathyroid calcium receptor mechanism defined by monoclonal antiparathyroid antibodies.

Parathyroid tissue from patients with hyperparathyroidism (HPT) exhibited reduced immunohistochemical reactivity with monoclonal antiparathyroid antibodies, previously shown to stain intensely the surface of normal human parathyroid cells and to interfere with a receptor mechanism of these cells which is involved in the sensing and gating of Ca2+. Parathyroid hormone (PTH) release and cytoplasmic Ca2+ concentrations (Ca2+i) of dispersed cells from the pathological parathyroid glands had right-shifted dependencies on extracellular Ca2+, and exposure to the antibodies rendered both Ca2+i and PTH release almost completely insensitive to changes in ambient Ca2+. The results suggest that reduced expression of a parathyroid calcium receptor mechanism may be an important cause for the aberrant PTH release in HPT.

Vitamin D receptor (VDR) and parathyroid hormone messenger ribonucleic acid levels correspond to polymorphic VDR alleles in human parathyroid tumors.

Calcitriol, via its receptor (VDR) is a main regulator of PTH secretion and parathyroid cell proliferation. Recently, marked overrepresentation of the polymorphic VDR alleles b, a, and T was found in patients with primary hyperparathyroidism (pHPT), which suggests pathogenic importance in the disease. Using the ribonuclease protection assay, relative VDR and PTH messenger ribonucleic acid (mRNA) levels of parathyroid adenomas from 42 patients with sporadic pHPT were related to these VDR polymorphisms. The tumors of patients homozygous for the b, a, or T alleles demonstrated significantly lower VDR and higher PTH mRNA levels than those exhibiting the BB, AA, or tt genotypes (P < 0.0001-0.02), whereas heterozygotes had intermediate values. A similar discrepancy was found when comparing the baT and non-baT haplotypes (0.042 +/- 0.005 vs. 0.064 +/- 0.004 for VDR; 34.4 +/- 3.7 vs. 21.6 +/- 2.2 for PTH; both P < 0.005). The lower VDR mRNA levels associated with the b, a, and T alleles may affect the calcitriol-mediated control of parathyroid function and thereby contribute to the development of sporadic pHPT.

Vitamin D receptor polymorphisms correlate to parathyroid cell function in primary hyperparathyroidism.

Calcitriol acts via its receptor (VDR) and inhibits PTH secretion and parathyroid cell proliferation. Increased prevalence of the polymorphic VDR alleles b, a, and T has been demonstrated in sporadic primary hyperparathyroidism. Sixty-two patients with primary hyperparathyroidism due to parathyroid adenoma (mean age, 69.5 +/- 1.4 yr) were genotyped for these VDR polymorphisms. Dispersed cells of the adenomas were exposed to increasing concentrations of extracellular Ca2+ and analyzed for PTH release and cytoplasmic Ca2+ concentrations. Ca2+-mediated PTH inhibition exhibited higher ED50 and less suppression in the cells of patients who were homozygous for the b, a, and T alleles (P < 0.05-0.10). When analyzing haplotypes, the patients with baT demonstrated a ED50 of 1.81 +/- 0.15 vs. 1.29 +/- 0.10 for BAt (P < 0.05). As VDR alleles were unrelated to parathyroid intracellular Ca2+, influences of polymorphic VDR alleles on PTH secretion seem to involve mechanisms other than the Ca2+-sensing protein of the parathyroid cell surface.

Reduced parathyroid vitamin D receptor messenger ribonucleic acid levels in primary and secondary hyperparathyroidism.

Vitamin D, via its receptor (VDR), inhibits the hormone secretion and proliferation of parathyroid cells. Vitamin D deficiency and reduced parathyroid VDR expression has been associated with development of hyperparathyroidism (HPT) secondary to uremia. VDR polymorphisms may influence VDR messenger RNA (mRNA) levels and have been coupled to an increased risk of parathyroid adenoma of primary HPT. VDR mRNA relative to glyceraldehyde-3-phosphate dehydrogenase mRNA levels were determined by RNase protection assay in 42 single parathyroid adenomas of patients with primary HPT, 23 hyperplastic glands of eight patients with uremic HPT, and 15 normal human parathyroid glands. The adenomas and hyperplasias demonstrated similar VDR mRNA levels, which were reduced (42 +/- 2.8% and 44 +/- 4.0%) compared with the normal glands (P < 0.0001). Comparison of parathyroid adenoma with a normal-sized parathyroid gland of the same individual (n = 3 pairs) showed a 20-58% reduction in the tumor. Nodularly enlarged glands represent a more advanced form of secondary HPT and showed greater reduction in the VDR mRNA levels than the diffusely enlarged glands (P < 0.005). The reduced VDR expression is likely to impair the 1,25(OH)2D3-mediated control of parathyroid functions, and to be of importance for the pathogenesis of not only uremic but also primary HPT. Circulating factors like calcium, PTH, and 1,25(OH)2D3 seem to be less likely candidates mediating the decreased VDR gene expression in HPT.

The vitamin D receptor (VDR) start codon polymorphism in primary hyperparathyroidism and parathyroid VDR messenger ribonucleic acid levels.

Vitamin D regulates parathyroid cell proliferation and secretion of PTH. Increased prevalence of the polymorphic vitamin D receptor (VDR) alleles b, a, and T has been reported in sporadic primary hyperparathyroidism (PHPT), suggesting that these genetic variants may predispose to the disease. Recently, another polymorphism in the VDR gene was related to bone mineral density, and this VDR-FokI polymorphism causes different lengths of the VDR, implying possible functional consequences. The VDR-FokI polymorphism was studied in 182 postmenopausal women with sporadic PHPT and in matched controls. No significant differences in distribution of the VDR-FokI genotypes could be detected between the groups, although there was a tendency toward overrepresentation of the F allele in the PHPT patients (P = 0.05). There were no significant associations with age, serum calcium, serum PTH, bone mineral density, or parathyroid tumor weight. The VDR genotypes were unrelated to VDR and PTH messenger ribonucleic acid levels in the parathyroid adenomas of 42 PHPT patients. In 23 PHPT patients, the Ca2+-PTH set-points were determined in vivo and were unrelated to the VDR alleles. We suggest that the VDR-FokI polymorphism has at most a minor pathogenic importance in the development of PHPT.

Clinical and genetic features of adrenocortical lesions in multiple endocrine neoplasia type 1.

In multiple endocrine neoplasia type 1 (MEN-1), benign enlargement of the adrenal cortex has been found in about one third of necropsy cases. To elucidate the clinical and genetic characteristics of the MEN-1 adrenal lesion, we have investigated 33 MEN-1 patients. Twelve individuals (37%) demonstrated adrenal enlargement, which was bilateral in 7 of them. Histopathology revealed diffuse and nodular cortical hyperplasia, adenomas, and a single case of adrenocortical carcinoma. The apparently benign adrenal enlargements were not associated with presently ascertainable biochemical disturbances in the hypothalamic-pituitary-adrenocortical axis, and they were without radiological signs of progression during follow-up. The individual developing unilateral adrenocortical carcinoma showed rapid adrenal expansion, feminization, and an abnormal urinary steroid profile after 4 yr of observation for bilateral minor adrenal enlargements. Pancreatic endocrine tumors were significantly overrepresented and present in all MEN-1 individuals with adrenal involvement. In agreement with findings in sporadic cases, the MEN-1 adrenocortical carcinoma genome showed loss of constitutional heterozygosity for alleles at 17p, 13q, 11p, and 11q. The benign adrenal lesions retained heterozygosity for the MEN-1 locus at chromosome 11 q 13. Despite its prevalence and malignant potential, the pituitary-independent adrenocortical proliferation does not appear to be a primary lesion in MEN-1, but might represent a secondary phenomenon, perhaps related to the pancreatic endocrine tumor.

Familial hypercalcemia and hypercalciuria caused by a novel mutation in the cytoplasmic tail of the calcium receptor.

Familial hyperparathyroidism (HPT), characterized by hypercalcemia and hypercalciuria, and familial benign hypocalciuric hypercalcemia (FHH) are the most common causes of hereditary hypercalcemia. The calcium-sensing receptor (CaR) regulates PTH secretion and renal calcium excretion. Heterozygous inactivating mutations of the gene cause FHH, whereas CaR gene mutations have not been demonstrated in HPT. In a kindred with 20 affected individuals, the hypercalcemic disorder segregated with inappropriately higher serum PTH and magnesium levels and urinary calcium levels than in unaffected members. Subtotal parathyroidectomy revealed parathyroid gland hyperplasia/adenoma and corrected the biochemical signs of the disorder in seven of nine individuals. Linkage analysis mapped the condition to markers flanking the CaR gene on chromosome 3q. Sequence analysis revealed a mutation changing phenylalanine to leucine at codon 881 of the CaR gene, representing the first identified point mutation located within the cytoplasmic tail of the CaR. A construct of the mutant receptor (F881L) was expressed in human embryonic kidney cells (HEK 293), and demonstrated a right-shifted dose-response relationship between the extracellular and intracellular calcium concentrations. The hypercalcemic disorder of the present family is caused by an inactivating point mutation in the cytoplasmic tail of the CaR and displays clinical characteristics atypical of FHH and primary HPT.

Parathyroid MEN1 gene mutations in relation to clinical characteristics of nonfamilial primary hyperparathyroidism.

Biochemical signs and severity of symptoms of primary hyperparathyroidism (pHPT) differ among patients, and little is known of any coupling of clinical characteristics of nonfamilial pHPT to genetic abnormalities in the parathyroid tumors. Mutations in the recently identified MEN1 gene at chromosome 11q13 have been found in parathyroid tumors of nonfamilial pHPT. Using microsatellite analysis for loss of heterozygosity (LOH) at 11q13 and DNA sequencing of coding exons, the MEN1 gene was studied in 49 parathyroid lesions of patients with divergent symptoms, operative findings, histopathological diagnosis, and biochemical signs of nonfamilial pHPT. Allelic loss at 11q13 was detected in 13 tumors, and 6 of them demonstrated previously unrecognized somatic missense and frameshift deletion mutations of the MEN1 gene. Many of the detected mutations would most likely result in a nonfunctional menin protein, consistent with a tumor suppressor mechanism. Clinical and biochemical characteristics of HPT were apparently unrelated to the presence or absence of LOH and the MEN1 gene mutations. However, the demonstration of LOH at 11q13 and MEN1 gene mutations in small parathyroid adenomas of patients with slight hypercalcemia and normal serum PTH levels suggest that altered MEN1 gene function may also be important for the development of mild sporadic pHPT.