Endocrinologic Emergencies

The endocrine system is a complex, coordinated, and highly regulated system that helps the body adapt to its constantly changing metabolic needs. One major endocrine-related disease, diabetes mellitus, is frequently seen in the emergency department (ED) and will be reviewed in some detail.

Basic Structure of the Endocrine System

The endocrine system is an interrelated network that enables the body to regulate a series of parameters to maintain a constant internal milieu (homeostasis) ( Fig. 12.1 ). The endocrine system relies on a series of glands . Glands are organized collections of cells located throughout the body that can both sense the levels of specific metabolites and secrete proteins, called hormones , into the bloodstream. Once released into the bloodstream, hormones circulate throughout the body and act on a variety of target organs. Under normal circumstances, the endocrine glands will either increase or decrease hormone secretion according to their own sensing mechanisms. By doing so, the endocrine system attempts to maintain specific set points for each regulated parameter. Disease occurs when the glands either secrete too much or too little hormone for the body’s circumstances at that time.

Signaling

The underlying concept of the endocrine system, autoregulation, is centered on feedback response loops as depicted in Fig. 12.2 . Regulation occurs via both positive and negative feedback loops that help maintain homeostasis. For many hormones, an area of the brain called the hypothalamus can sense the level of a given hormone. It can then up- or downregulate its secretion of a “releasing hormone” that acts on the pituitary, which in turn produces another series of hormones that directly regulates the hormone production of many of the endocrine glands scattered throughout the body. Having an elevated serum level of any hormone will generally inhibit its own secretion through a negative feedback loop to avoid an adverse response in peripheral tissues to excessively high hormone levels. Similarly, when levels of that hormone fall, the hypothalamus is triggered to stimulate the pituitary, which in turn secretes a hormone to stimulate the production of the target hormone, creating a positive feedback loop.

Another example of endocrinologic system regulation is when a pair of hormones exists that act in opposite ways. The best example of this is how the body regulates serum glucose levels. When the serum glucose starts to rise, as would happen after a meal, the pancreas will secrete insulin that facilitates the entry of glucose into muscles and fat cells and lowers the blood glucose level. During periods of fasting, blood sugar is maintained by the pancreatic secretion of a different hormone, glucagon, that stimulates release of glucose from storage sites in the liver and other organs.

Some common hormones and their functions are outlined in Table 12.1 . The table displays common signs and symptoms of hormone imbalances that can be recognized in the ED. When viewing patients in the ED, some common features listed below require prompt recognition of classic features to allow for expedient management and to ensure these patients are on monitoring early with proper escalation of care.

Table 12.1

Common Hormones Involved in Emergency Department Presentations and the Consequences of High and Low Levels

Gland	Hormone	Main Functions	Too Much?	Too Little?
Adrenal	Aldosterone Corticosteroids	Regulates salt, water balance, and blood pressure	Hypertension Confusion Hyperglycemia Obesity	Hypotension Confusion Hypoglycemia
Pancreas	Insulin Glucagon	Regulates glucose levels	Hypoglycemia	Hyperglycemia
Parathyroid	Parathyroid hormone	Maintain calcium homeostasis	Kidney stones Abdominal pain Lethargy Confusion	Tingling Muscle aches Seizures Tetany
Pituitary	Multiple	Helps regulate the function of most of the endocrine glands
Thyroid	Thyroid hormones (T3 and T4)	Regulates cellular metabolism	Tachycardia Tremors Confusion Hypertension Weight loss	Bradycardia Weight gain Lethargy