Hypoglycemia
Hypoglycemic symptoms and manifestations can be divided into those produced by the counterregulatory hormones (epinephrine/adrenaline and glucagon) triggered by the falling glucose, and the neuroglycopenic effects produced by the reduced brain sugar.Not all of the above manifestations occur in every case of hypoglycemia. There is no consistent order to the appearance of the symptoms, if symptoms even occur. Specific manifestations may also vary by age, by severity of the hypoglycemia and the speed of the decline. In young children, vomiting can sometimes accompany morning hypoglycemia with ketosis. In older children and adults, moderately severe hypoglycemia can resemble mania, mental illness, drug intoxication, or drunkenness. In the elderly, hypoglycemia can produce focal stroke-like effects or a hard-to-define malaise. The symptoms of a single person may be similar from episode to episode, but are not necessarily so and may be influenced by the speed at which glucose levels are dropping, as well as previous incidents.
Glutamate dehydrogenase 1
Familial hyperinsulinism, linked to mutations in GLUD1, is characterized by hypoglycemia that ranges from severe neonatal-onset, difficult-to-manage disease to childhood-onset disease with mild symptoms and difficult-to-diagnose hypoglycemia. Neonatal-onset disease manifests within hours to two days after birth. Childhood-onset disease manifests during the first months or years of life. In the newborn period, presenting symptoms may be nonspecific, including seizures, hypotonia, poor feeding, and apnea. In severe cases, serum glucose concentrations are typically extremely low and thus easily recognized, whereas in milder cases, variable and mild hypoglycemia may make the diagnosis more difficult. Even within the same family, disease manifestations can range from mild to severe. Individuals with autosomal recessive familial hyperinsulinism, caused by mutations in either ABCC8 or KCNJ11 (FHI-KATP), tend to be large for gestational age and usually present with severe refractory hypoglycemia in the first 48 hours of life; affected infants usually respond only partially to diet or medical management (i.e., diazoxide therapy) and thus may require pancreatic resection. Individuals with autosomal dominant FHI-KATP tend to be appropriate for gestational age at birth, to present at approximately age one year (range: 2 days - 30 years), and to respond to diet and diazoxide therapy. Exceptions to both of these generalities have been reported. FHI-GCK, caused by mutations in GCK, may be much milder than FHI-KATP; however, some persons have severe, diazoxide-unresponsive hypoglycemia. FHI-HADH, caused by mutations in HADH, tends to be relatively mild, although severe cases have been reported. Individuals with FHI-HNF4A, caused by mutations in HNF4A, are typically born large for gestational age and have mild features that respond to diazoxide treatment. FHI-UCP2, caused by mutations in UCP2, is a rare cause of diazoxide-responsive FH1. Hyperammonemia/hyperinsulinism (HA/HI) is associated with mild-to-moderate hyperammonemia and with relatively mild, late-onset hypoglycemia; most but not all affected individuals have mutations in GLUD1.