Frontiers of Hormone Research最新文献

A time-dependent loss of cell solute protects against lethal cerebral edema in hyponatremia. This adaptation, which makes survival possible when the serum sodium concentration is extremely low, also makes the brain vulnerable to injury if chronic (>48 hours) hyponatremia is corrected more rapidly than lost brain solutes can be recovered. Rapid correction of chronic hyponatremia results in programmed cell death of astrocytes and oligodendrocytes and presents clinically with a delayed onset of neurological findings, known as the osmotic demyelination syndrome. This iatrogenic complication can be avoided by limiting correction of hyponatremia to <8 mEq/L per day.

Exercise-associated hyponatremia (EAH) refers to below-normal serum sodium concentrations [Na+] that develop during exercise. The pathogenesis of EAH is best described as a spectrum ranging between profound polydipsia to modest sweat sodium losses with hypovolemia and relative dilution. Non-osmotic arginine vasopressin (AVP) remains the unifying pathogenic stimulus to abnormal renal water retention in acute symptomatic EAH. Cases of hyponatremia are mostly reported after endurance sports, but are also observed after shorter duration events and in team sport athletes. The signs and symptoms of EAH are vague, and include bloating, vomiting, headache, and altered mental status. A diagnosis of EAH can only be confirmed by a blood test, whereas signs/symptoms guide the most appropriate treatment strategy. Mild-to-moderate EAH (without encephalopathy) can be treated with either fluid restriction or an oral bolus of a hypertonic saline solution. Severe EAH (with encephalopathy) is a life-threatening emergency and should be urgently treated with intravenous 100 mL boluses of 3% saline until the resolution of encephalopathy symptoms. The prevention of EAH is evolutionarily rooted in preventing overdrinking during exercise. Drinking according to the dictates of thirst is the most individualized strategy to prevent life-threatening dysnatremia during exercise, regardless of sport.

The treatment of hypoparathyroidism depends on the severity of hypocalcemia, how rapidly the hypocalcemia developed, and the symptomatology. Chronic hypoparathyroidism is usually treated with oral supplementations, including calcium, calcitriol, or other active vitamin D analogs, and at times, thiazide diuretics. Although the standard therapy can adequately control patients with this disease, sometimes very high doses are required to maintain serum calcium levels in the normal range, with poor compliance and risk of long-term complications.

Individuals with a familial predisposition to the development of parathyroid tumors constitute a small minority of all patients with primary hyperparathyroidism (PHPT). These familial syndromes exhibit Mendelian inheritance patterns and the main causative genes in most families have been identified. They include multiple endocrine neoplasia (MEN; types 1, 2A, and 4), hyperparathyroidism-jaw tumor (HPT-JT) syndrome, familial isolated hyperparathyroidism, familial hypocalciuric hypercalcemia (FHH), and neonatal severe PHPT. Each MEN type is associated with the various combinations of specific tumors. MEN1 is characterized by the occurrence of parathyroid, enteropancreatic, and pituitary tumors; MEN2A is characterized by medullary thyroid carcinoma and pheochromocytoma, and MEN4 is characterized by a pathological spectrum similar to that of MEN1 in association with tumors of the adrenal, kidney, and reproductive organs. HPT-JT is characterized by PHPT, ossifying fibromas of maxillary bones, kidney disease, and uterine neoplasias. The prompt diagnosis of these diseases is of great importance for planning appropriate surveillance of the mutant carriers and correct surgical management. The search for mutation is also useful for the identification of the family members who do not carry the mutation and can avoid unnecessary biochemical and instrumental evaluations. Surgery remains the treatment of choice in all familial forms except FHH.

Asymptomatic primary hyperparathyroidism has become the most common presentation of primary hyperparathyroidism in Europe and North America, and an increasingly common presentation in other parts of the world. As many as 25% of asymptomatic patients may develop indications for parathyroidectomy when followed long-term for up to 15 years. Patients who remain asymptomatic should be monitored for the development of complications that justify surgery. Patients who become symptomatic should be referred for surgery. Surgery may improve quality of life even in patients who remain asymptomatic.