Endocrine manifestations of critical illness in the child.

The stress response in humans commonly includes elevations in plasma concentrations of glucocorticoids, catecholamines, glucagon, growth hormone, aldosterone, and renin, resulting in alterations in the metabolism of glucose and other energy substrates, and in increased sodium and water retention. In severe illness, triiodothyronine and sometimes thyroxine are decreased without evidence of clinical hypothyroidism. Antidiuretic hormone may be elevated in bacterial meningitis and other central nervous system disorders, as well as in acute asthma, chronic ventilator therapy, pneumothorax, atelectasis, and postoperatively. Increased ADH concentration can lead to significant hypoosmolality and hyponatremia with adverse effects on the patient. In the setting of severe intracerebral insults, ADH may be inappropriately low, resulting in diabetes insipidus. Insulin concentrations may be inappropriately low for serum glucose concentration, or insulin may have diminished receptor responsiveness in seriously stressed patients. Either situation leads to hyperglycemia. Disturbances in calcium, phosphorus, and magnesium homeostasis may occur relatively frequently in the critically ill patient in response to therapeutic interventions, or illness-induced altered metabolism. It is not always clear when an altered metabolic or hormonal state is an appropriate response to a stress, or represents decompensation of the body's mechanisms for coping with that stress. It is important, however to recognize the common responses of the organism to severe illness, and to monitor for treatable abnormalities which occur.