Göran Åkerström

K+ Channel Mutations in Adrenal Aldosterone-Producing Adenomas and Hereditary Hypertension

Potassium channel mutations drive both cell growth and hormone production in an adrenal tumor that causes severe hypertension. Endocrine tumors such as aldosterone-producing adrenal adenomas (APAs), a cause of severe hypertension, feature constitutive hormone production and unrestrained cell proliferation; the mechanisms linking these events are unknown. We identify two recurrent somatic mutations in and near the selectivity filter of the potassium (K+) channel KCNJ5 that are present in 8 of 22 human APAs studied. Both produce increased sodium (Na+) conductance and cell depolarization, which in adrenal glomerulosa cells produces calcium (Ca2+) entry, the signal for aldosterone production and cell proliferation. Similarly, we identify an inherited KCNJ5 mutation that produces increased Na+ conductance in a Mendelian form of severe aldosteronism and massive bilateral adrenal hyperplasia. These findings explain pathogenesis in a subset of patients with severe hypertension and implicate loss of K+ channel selectivity in constitutive cell proliferation and hormone production.

Fibroblast growth factor-23 regulates parathyroid hormone and 1alpha-hydroxylase expression in cultured bovine parathyroid cells

Fibroblast growth factor-23 (FGF23) is a circulating factor that decreases serum levels of inorganic phosphate (Pi) as well as 1,25-dihydroxyvitamin D(3). Recent studies also suggest a correlation between serum levels of FGF23 and parathyroid hormone (PTH) in patients with chronic kidney disease. It is, however, unknown whether FGF23 directly modulates PTH expression, or whether the correlation is secondary to abnormalities in Pi and vitamin D metabolism. The objective of the current study was therefore to elucidate possible direct effects of FGF23 on bovine parathyroid cells in vitro. Treatment of parathyroid cells with a stabilized form of recombinant FGF23 (FGF23(R176Q)) induced a rise in early response gene-1 mRNA transcripts, a marker of FGF23 signaling. FGF23(R176Q) potently and dose-dependently decreased the PTH mRNA level within 12 h. In agreement, FGF23(R176Q) also decreased PTH secretion into conditioned media. In contrast, FGF23(R176Q) dose-dependently increased 1alpha-hydroxylase expression within 3 h. FGF23 (R176Q) did not affect cell viability nor induce apoptosis, whereas a small but significant increase in cell proliferation was found. We conclude that FGF23 is a negative regulator of PTH mRNA expression and secretion in vitro. Our data suggest that FGF23 may be a physiologically relevant regulator of PTH. This defines a novel function of FGF23 in addition to the previously established roles in controlling vitamin D and Pi metabolism.

Somatic and germline CACNA1D calcium channel mutations in aldosterone-producing adenomas and primary aldosteronism

Adrenal aldosterone-producing adenomas (APAs) constitutively produce the salt-retaining hormone aldosterone and are a common cause of severe hypertension. Recurrent mutations in the potassium channel gene KCNJ5 that result in cell depolarization and Ca2+ influx cause ∼40% of these tumors. We identified 5 somatic mutations (4 altering Gly403 and 1 altering Ile770) in CACNA1D, encoding a voltage-gated calcium channel, among 43 APAs without mutated KCNJ5. The altered residues lie in the S6 segments that line the channel pore. Both alterations result in channel activation at less depolarized potentials; Gly403 alterations also impair channel inactivation. These effects are inferred to cause increased Ca2+ influx, which is a sufficient stimulus for aldosterone production and cell proliferation in adrenal glomerulosa. We also identified de novo germline mutations at identical positions in two children with a previously undescribed syndrome featuring primary aldosteronism and neuromuscular abnormalities. These findings implicate gain-of-function Ca2+ channel mutations in APAs and primary aldosteronism.

Population-based screening for primary hyperparathyroidism with serum calcium and parathyroid hormone values in menopausal women

BACKGROUND Population-based screenings for primary hyperparathyroidism have failed to systematically use intact parathyroid hormone (PTH) values for diagnosis, to explore prevalence and diagnostic criteria of normocalcemic hyperparathyroidism, and to attempt surgical verification of the disorder. METHODS A total of 5202 women (ages, 55 to 75 years) attending a population-based mammography screening were investigated for primary hyperparathyroidism. In women lacking a family history of hypercalcemia, significant renal impairment, or low urinary calcium excretion hyperparathyroidism was diagnosed on the basis of predetermined criteria encompassing lower intact serum PTH levels in hypercalcemia (serum PTH 25 ng/L or greater; reference range, 12 to 55 ng/L) than in two intervals of normocalcemia (serum PTH 35 or greater, greater than 55 ng/L). RESULTS Prevalence of hyperparathyroidism was 2.1% (n = 109). At diagnosis total serum calcium and serum PTH levels were 2.32 to 3.19 mmol/L and 34 to 300 ng/L, respectively, and 66% of the women exhibited normocalcemia. Repeated examination showed persistent normocalcemia in 30 patients, and all but two of them had normal ionized plasma calcium levels. Significantly higher serum calcium, serum PTH, and urine calcium--but not serum creatinine--levels were found in patients with hyperparathyroidism compared with matched control subjects from the screened population. Within an ongoing stratified treatment program, 59 of 60 patients who underwent operation exhibited pathologic parathyroid tissue (mean weight, 591 mg). CONCLUSIONS Substantial prevalence of sporadic primary hyperparathyroidism is demonstrated in a risk group. Although criteria for hyperparathyroidism recognition included patients with truly mild biochemical derangement, operative findings suggested underdiagnosis of the disorder.

ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: Towards a Standardized Approach to the Diagnosis of Gastroenteropancreatic Neuroendocrine Tumors and Their Prognostic Stratification

ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors : towards a standardized approach to the diagnosis of gastroenteropancreatic neuroendocrine tumors and their prognostic stratification

Effect of Surgery on the Outcome of Midgut Carcinoid Disease with Lymph Node and Liver Metastases

We have evaluated survival and tumor-related symptoms in the presence of mesenteric lymph node and liver metastases in relation to surgical procedures in 314 patients (148 women, mean age at diagnosis 61 years; 249 with liver metastases) treated for midgut carcinoid tumors. Of the operated patients, 46% presented with severe abdominal pain and intestinal obstruction and were operated on before the diagnosis. Medical treatment (somatostatin analogs, interferon-a) was initiated in 67% and 86%, respectively. Surgical attempts included small intestine or ileocecal/right-sided colon resection with excision of mesenteric lymph node metastases. Most of the patients (n = 286) had mesenteric lymph node metastases; 33% of them had unresectable mesenteric lymph node metastases and underwent surgery without mesenteric dissection. Patients who underwent resection for the primary tumor had a longer survival than those with no resection (median survival 7.4 vs. 4.0 years; p <0.01). Patients who underwent successful excision of mesenteric metastases had a significantly longer survival than those with remaining lymph node metastases. Patients operated on for a primary tumor but with remaining lymph nodes but no liver metastases and who subsequently received interferon and somatostatin analog treatment had a median survival of 7.4 years. Resection of the primary tumor and the mesenteric lymph node metastases led to a significant reduction in tumor-related symptoms. Surgery to remove the primary intestinal tumor including mesenteric lymph node metastases is supported by the present results, even in the presence of liver metastases. Liver metastases and significant preoperative weight loss are identified as major negative prognostic factors for survival.

Autoimmune Polyendocrine Syndrome Type 1 and NALP5, a Parathyroid Autoantigen

BACKGROUND Autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disorder caused by mutations in AIRE, the autoimmune regulator gene. Though recent studies concerning AIRE deficiency have begun to elucidate the molecular pathogenesis of organ-specific autoimmunity in patients with APS-1, the autoantigen responsible for hypoparathyroidism, a hallmark of APS-1 and its most common autoimmune endocrinopathy, has not yet been identified. METHODS We performed immunoscreening of a human parathyroid complementary DNA library, using serum samples from patients with APS-1 and hypoparathyroidism, to identify patients with reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5). Subsequently, serum samples from 87 patients with APS-1 and 293 controls, including patients with other autoimmune disorders, were used to determine the frequency and specificity of autoantibodies against NALP5. In addition, the expression of NALP5 was investigated in various tissues. RESULTS NALP5-specific autoantibodies were detected in 49% of the patients with APS-1 and hypoparathyroidism but were absent in all patients with APS-1 but without hypoparathyroidism, in all patients with other autoimmune endocrine disorders, and in all healthy controls. NALP5 was predominantly expressed in the cytoplasm of parathyroid chief cells. CONCLUSIONS NALP5 appears to be a tissue-specific autoantigen involved in hypoparathyroidism in patients with APS-1. Autoantibodies against NALP5 appear to be highly specific and may be diagnostic for this prominent component of APS-1.

Tissue Distribution of Human gp330/Megalin, a Putative Ca2+-sensing Protein

We used riboprobes and monoclonal antibodies to characterize tissue distribution of the human 550-kD homologue to gp330/megalin, primarily identified in the rat kidney. Human gp330/megalin mRNA and protein are readily identified in human parathyroid cells, placental cytotrophoblasts, kidney proximal tubule cells, and epididymal epithelial cells. The immunoreactivity is found on the surface of the cells and is heterogeneously downregulated in parathyroid hyperplasia and adenomas. Cells of the proximal kidney tubule and epididymis express the protein on their luminal aspect. Moreover, the protein is expressed in Type II pneumocytes, mammary epithelial and thyroid follicular cells, and the ciliary body of the eye. Sequence analysis of cDNA fragments, obtained by RT-PCR, revealed identical nucleotide sequences in parathyroid, kidney, placenta, epididymis, and lung. Immunohistochemistry for parathyroid hormone-related protein (PTHrP) revealed partial co-expression with human gp330/megalin in parathyroid, placenta, and mammary gland. The findings substantiate human gp330/megalin expression in a variety of human tissues expected to possess calcium-sensing functions. It may constitute a protein of utmost importance to adult and fetal calcium homeostasis, although other important functions may also be coupled to this exceptionally large protein with highly restricted tissue distribution. (J Histochem Cytochem 45:383–392, 1997)

SURVIVAL AND RENAL FUNCTION IN UNTREATED HYPERCALCAEMIA: Population-based Cohort Study with 14 Years of Follow-up

172 persons with mild to moderate hypercalcaemia were followed up for 14 years. Life-table analyses showed that, among persons aged 70 years or less at the time of detection of the hypercalcaemia, survival was lower in the hypercalcaemic group than in a normocalcaemic age and sex matched control group. No such difference was found among older persons. The lower survival was related to degree of hypercalcaemia, and this held true when systolic and diastolic blood pressure, serum glucose, serum uric acid, and serum cholesterol were taken into account in a multivariate analysis. The lower survival seemed to be due mainly to deaths from diseases of the circulatory organs. No person with normal renal function at the beginning of the study period had a more than marginally raised serum creatinine at follow-up.

Prevalence of hypercalcaemia in a health survey: a 14‐year follow‐up study of serum calcium values

Abstract. Among 16 401 subjects attending two health screenings, in 1969 and 1971, 176 showed hypercalcaemia on both occasions, i.e. serum calcium values above 2·60 mmol l‐1. The prevalence of hypercalcaemia increased in women with advancing age and occurred in close to 3% of those above the age of 60, whilst in men it was found in less than 0·7% in all age groups. The mean serum calcium concentration in women above the age of 50 was significantly higher than in men. This observation could at least partly explain why hyperparathyroidism (HPT) is more often diagnosed in females. Only nine persons were initially referred for neck exploration. Most of the others were not even notified of the biochemical disturbance and thus it was possible to study the serum calcium values in an unattended cohort until follow‐up after 14 years. In the hypercalcaemic patients there was little or no increase in serum calcium during these years. In no patient did the serum calcium level rise above 3·0 mmol l‐1. Altogether, 24 patients from the initial cohort were subsequently operated on for primary HPT but there were only two further cases of verified HPT, which developed during the follow‐up period, in those who had been clearly normocalcaemic at the health surveys. In conclusion, hypercalcaemia, presumably caused by primary HPT, is common but apparently develops slowly and with little risk of a progressive rise of serum calcium concentrations.