The Ca2+-sensing receptor (CaSR) is a dimeric family C G protein-coupled receptor that is expressed in calcitropic tissues such as the parathyroid glands and the kidneys and signals via G proteins and β-arrestin. The CaSR has a pivotal role in bone and mineral metabolism, as it regulates parathyroid hormone secretion, urinary Ca2+ excretion, skeletal development and lactation. The importance of the CaSR for these calcitropic processes is highlighted by loss-of-function and gain-of-function CaSR mutations that cause familial hypocalciuric hypercalcaemia and autosomal dominant hypocalcaemia, respectively, and also by the fact that alterations in parathyroid CaSR expression contribute to the pathogenesis of primary and secondary hyperparathyroidism. Moreover, the CaSR is an established therapeutic target for hyperparathyroid disorders. The CaSR is also expressed in organs not involved in Ca2+ homeostasis: it has noncalcitropic roles in lung and neuronal development, vascular tone, gastrointestinal nutrient sensing, wound healing and secretion of insulin and enteroendocrine hormones. Furthermore, the abnormal expression or function of the CaSR is implicated in cardiovascular and neurological diseases, as well as in asthma, and the CaSR is reported to protect against colorectal cancer and neuroblastoma but increase the malignant potential of prostate and breast cancers.

The calcium-sensing receptor in physiology and in calcitropic and noncalcitropic diseases.

Autoimmune forms of hypoglycemia are a rare cause of low blood sugar levels among Caucasians, and often go misdiagnosed, exposing patients to lengthy series of pointless, potentially harmful and expensive tests. There are two types of autoimmune hypoglycemia. One is insulin autoimmune syndrome (IAS), which is characterized by hyperinsulinemic hypoglycemia, elevated insulin autoantibody (IAA) titers, no prior exposure to exogenous insulin, and no of pathological abnormalities of the pancreatic islets. This condition is also known as “Hirata’s disease”. The other is type B insulin resistance syndrome (TBIRS), a rare autoimmune disorder resulting in a broad array of abnormalities in glucose homeostasis—from hypoglycemia to extremely insulin-resistant hyperglycemia—caused by the presence of insulin receptor autoantibodies (IRAbs). This review focuses on these two syndromes, describing their epidemiology, possible genetic background, clinical presentation, pathophysiology, diagnosis and treatment.

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Insulin autoimmune syndrome: from diagnosis to clinical management.

Insulin autoimmune syndrome (IAS) is considered to be very rare in Caucasians. Understanding its pathophysiology is paramount in (a) appreciating its potential impact on analyses of pancreatic hormones and (b) explaining its highly variable clinical manifestations in non-diabetic, non-acutely ill patients with indeterminate hypoglycaemia. The underlying aetiology of IAS is the presence of variable affinity/avidity endogenous insulin antibodies in significant amounts. The two types of insulin antibodies namely antibodies which bind insulin and/or proinsulin(s) and receptor antibodies (insulin mimetic) will be discussed. Their biochemical and immunological roles in causing hypoglycaemia will be highlighted. Clinical manifestations of IAS can vary from mild and transient to spontaneous, severe and protracted hypoglycaemia necessitating in extreme cases plasmapheresis for glycaemic control. Antibodies of IAS can interfere in pancreatic immunoassay tests causing erroneous and potentially misleading results. Thorough testing for endogenous insulin antibodies must be considered in the investigations of non-diabetic, non-acutely ill patients with indeterminate and/or unexplained hypoglycaemia.

The insulin autoimmune syndrome (IAS) as a cause of hypoglycaemia: an update on the pathophysiology, biochemical investigations and diagnosis

Insulin autoimmune syndrome (IAS), also named Hirata's disease, is a rare condition characterized by hypoglycemic episodes due to the presence of high titers of insulin autoantibodies (IAA). IAS is a form of immune-mediated hypoglycemia, which develops when a triggering factor (ie, a medication or a viral infection) acts on an underlying predisposing genetic background. IAS pathogenesis involves the formation of insulin-IAA complexes that induce glycemic alterations with a double-phase mechanism: IAA prevent insulin to bind its receptor in the postprandial phase, possibly resulting in mild hyperglycemia; thereafter, insulin is released from the complexes irrespective of blood glucose concentrations, thus inducing hypoglycemia. The diagnosis of IAS is challenging, requiring a careful workup aimed at excluding other causes of hyperinsulinemic hypoglycemia. The gold standard for the definitive diagnosis is the finding of IAA in a blood sample. Because IAS is frequently a self-remitting disease, its management mostly consists of supportive measures, such as dietary modifications, aimed at preventing the development of hypoglycemia. Pharmacological therapies may occasionally be necessary for patients presenting with severe manifestations of IAS. Available therapies may include drugs that reduce pancreatic insulin secretion (somatostatin analogues and diazoxide, for instance) and immunosuppressive agents (glucocorticoids, azathioprine and rituximab). The purpose of this review is to provide a comprehensive analysis of the disease, by describing the burden of knowledge that has been obtained in the 50 years following its first description, took in 1970, and by highlighting the points that are still unclear in its pathogenesis and management.

https://www.dovepress.com/getfile.php?fileID=57175

Insulin Autoimmune Syndrome (Hirata Disease): A Comprehensive Review Fifty Years After Its First Description.

Subclinical hypothyroidism (SH) is biochemically defined as serum TSH levels above the upper limit of the reference range in the presence of normal free T4 (FT4) concentrations While there is a general agreement to treat subjects with serum TSH levels above 10 mU/L, the management of mild form (TSH concentrations between 45 and 10 mU/L) is still a matter of debate In children, mild SH is often a benign and remitting condition and the risk of progression to overt thyroid dysfunction depends on the underlying condition, being higher in the autoimmune forms The major concern is to establish whether SH in children should always be considered an expression of mild thyroid dysfunction and may deserve treatment Current data indicate that children with mild SH have normal linear growth, bone health and intellectual outcome However, slight metabolic abnormalities and subtle deficits in specific cognitive domains have been reported in children with modest elevation of TSH concentration Although these findings are not sufficient to recommend levothyroxine treatment for all children with mild SH, they indicate the need for regular monitoring to ensure early identification of children who may benefit from treatment In the meanwhile, the decision to initiate therapy in children with mild SH should be based on individual factors

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MANAGEMENT OF ENDOCRINE DISEASE Subclinical hypothyroidism in children

The calcium sensing receptor (CASR) is expressed most abundantly in the parathyroid glands and the kidney. CASR regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. Inactivating mutations in the CASR gene may result in disorders of calcium homeostasis manifesting as familial benign hypocalciuric hypercalcemia (FBHH) and neonatal severe hyperparathyroidsm (NSHPT). Two cases were referred with severe hypercalcemia in the neonatal period. Laboratory evaluation revealed severe hypercalcemia and elevated PTH. The parents also had mild hypercalcemia. The serum calcium level did not normalize with conventional hypercalcemia treatment and there was also no response to cinacalcet in case 1. Total parathyroidectomy was performed when the patient was 70 days old. Genetic analysis revealed a novel homozygous p.Arg544* mutation in the CASR gene. Case 2 underwent total parathyroidectomy and autoimplantation when she was 97 days old, but the parathyroid gland implanted into the forearm was removed 27 days later because the hypercalcemia continued. Genetic evaluation revealed a novel homozygous p.Pro682Leu mutation with normal anthropometric measurements. The neurological development is consistent with age in both cases while case 2 has mild mental retardation. No bone deformity or fracture is present in either case and normocalcemia is ensured with calcitriol in both cases.

Treatment experience and long-term follow-up data in two severe neonatal hyperparathyroidism cases.

Background: Insulin autoimmune syndrome (IAS) is a condition characterized by hypoglycemia associated with the presence of autoantibodies to insulin in patients who have not been injected with insulin. Case Report: A female patient (aged 16 years and 3 months) presented with the complaint of being overweight. Physical examination revealed a body weight of 78.2 kg (+2.6 SD) and a height of 167 cm (+0.73 SD). While the patient's fasting blood glucose level was found to be 40 mg/dl, blood ketone was negative and the serum insulin level was determined as 379 mIU/ml. The patient was diagnosed with hyperinsulinemic hypoglycemia. Abdominal ultrasound, pancreas MRI and endoscopic ultrasound were normal. The daily blood glucose profile revealed postprandial hyperglycemia and reactive hypoglycemia in addition to fasting hypoglycemia. The results of anti-insulin antibody measurements were as high as 41.8% (normal range 0-7%). A 1,600-calorie diet containing 40% carbohydrate and divided into 6 meals a day was given to the patient. Simple sugars were excluded from the diet. Hypoglycemic episodes were not observed, but during 2 years of observation, serum levels of insulin and anti-insulin antibodies remained elevated. Conclusion: In all hyperinsulinemic hypoglycemia cases, IAS should be considered in the differential diagnosis and insulin antibody measurements should be carried out.

An uncommon cause of hypoglycemia: insulin autoimmune syndrome.

Background The aim of our study was to evaluate clinical, laboratory and imaging findings and to have an idea about the clinical course of subclinical hypothyroidism in children. Methods Our study included 25 patients who were diagnosed with non-autoimmune subclinical hypothyroidism without goitre, between the ages of 3 and 18 and with body mass index (BMI) below the 85th percentile. Results The mean thyroid-stimulating hormone (TSH) level was 6.92±0.92 μIU/mL at diagnosis, 4.77±1.57 μIU/mL in the third month and 4.51±1.79 μIU/mL in the first year of follow-up. About 73.7% of subclinical hypothyroidism was recovered. There was no statistically significant difference between heart rate, diastolic blood pressure, lipid profile, fasting blood glucose (FBG), fasting insulin level, homeostatic model assessment of insulin resistance (HOMA-IR), hemoglobin, white blood cell, platelet, C-reactive protein (CRP) levels and thyroid volume at diagnosis and in the first year of follow-up. In the first year of follow-up, systolic blood pressure and high-sensitivity CRP value were significantly higher than at diagnosis. However, it was observed that these values were similar in the present group with subclinical hypothyroidism. Conclusions We concluded that there was no progression to overt hypothyroidism during 1-year follow-up and that subclinical hypothyroidism had no effect on height standard deviation score (SDS), BMI SDS, blood pressure, glucose and lipid metabolism during follow-up without treatment.

Follow-up in children with non-obese and non-autoimmune subclinical hypothyroidism

Treatment Experience and Long-Term Follow-Up Data in Two Severe Neonatal Hyperparathyroidism Cases

Objective The onset of puberty in children is occurring at an increasingly earlier ages. During the coronavirus 2019 pandemic, children experienced epidemic-related changes such as stress, sedentary lifestyle, and weight gain. Materials and Methods Auxological, clinical, endocrinological, and radiological data in the files of 57 patients who were given gonadotropin-releasing hormone analog therapy with the diagnosis of central precocious puberty between April 1 and July 1, 2019 (group 1) and April 1 and July 1, 2020 (group 2) were analyzed retrospectively. Results A total of 27 patients (26 girls, 1 boy) in group 1 and 30 patients (28 girls, 2 boys) in group 2 were diagnosed with central precocious puberty. Mean ages at diagnosis for groups 1 and 2 were 28.54 ± 0.94 and 7.92 ± 0.96 years, respectively (P = .018). Mean bone age at diagnosis for group 1 was 9.78 ± 1.48 (6.8-12), and for group 2 it was 8.78 ± 1.11 (6.5-12) years (P = .013). The mean age of starting treatment in groups 1 and 2 was 8.94 ± 0.17 (6.8-9.8) and 8.07 ± 0.02 (5.8-10) years, respectively (P = .002). Average birth weights for groups 1 and 2 were 950 ± 1100 (2300-3400) and 3180 ± 717 (870-3820) g, respectively (P = .012). Treatment was started when breast stage was T3 in 57.69% of group 1 and T2 in 75% of group 2, and a statistical difference was found between them (P = .006) and uterine length was higher in group 2 (P = .144). Conclusion: During the coronavirus 2019 pandemic, patients who start central precocious puberty therapy were of younger age. In our single-center experience, coronavirus 2019 was not seen to have a significant impact on central precocious puberty.

Senay Savas-Erdeve

Papers

Treatment experience and long-term follow-up data in two severe neonatal hyperparathyroidism cases.

An uncommon cause of hypoglycemia: insulin autoimmune syndrome.

Follow-up in children with non-obese and non-autoimmune subclinical hypothyroidism

Treatment Experience and Long-Term Follow-Up Data in Two Severe Neonatal Hyperparathyroidism Cases

Status of Central Precocious Puberty Cases at the Onset of Coronavirus Disease 2019 Pandemic: A Single-Center Experience