Editing Anatomy and Physiology (section)

== Endocrine System ==

The endocrine system uses hormones carried in the bloodstream for slow, widespread, sustained regulation, in contrast to the fast and targeted nervous system.

* '''Hypothalamus''': controls the pituitary and links the nervous and endocrine systems.
* '''Anterior pituitary''': growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin.
* '''Posterior pituitary''': stores and releases '''antidiuretic hormone (ADH)''' and oxytocin. ADH causes water reabsorption in the collecting ducts. Too little ADH causes diabetes insipidus with large volumes of dilute urine and hypernatremia; too much causes the syndrome of inappropriate antidiuretic hormone with water retention, concentrated urine, and dilutional hyponatremia.
* '''Thyroid''': triiodothyronine and thyroxine set metabolic rate; '''calcitonin''' lowers serum calcium by moving it into bone.
* '''Parathyroid''': '''parathyroid hormone''' raises serum calcium by pulling it from bone, increasing renal reabsorption, and activating vitamin D for gut absorption. Parathyroid hormone and calcium move together; calcium and phosphorus move in opposite directions.
* '''Adrenal cortex''': '''aldosterone''' (a mineralocorticoid) retains sodium and water and excretes potassium; '''cortisol''' (a glucocorticoid) raises glucose, suppresses inflammation and immunity, and follows a diurnal rhythm.
* '''Adrenal medulla''': epinephrine and norepinephrine, the hormonal arm of the sympathetic response.
* '''Pancreas''': alpha cells secrete '''glucagon''' (raises glucose), beta cells secrete '''insulin''' (moves glucose and potassium into cells), delta cells secrete somatostatin.

'''Nursing application:'''
* Insulin drives potassium into cells, which is why insulin with dextrose is used to treat hyperkalemia and why hypokalemia can develop during treatment of diabetic ketoacidosis. Potassium must be monitored closely.
* Aldosterone's sodium-water-retention and potassium-wasting profile explains the electrolyte pattern in Addison disease (low sodium, high potassium, hypotension, hypoglycemia) versus Cushing syndrome (high sodium, low potassium, hypertension, hyperglycemia).
* Abrupt withdrawal of long-term corticosteroids can precipitate adrenal crisis because exogenous steroid suppresses the hypothalamic-pituitary-adrenal axis. Steroids must be tapered.
* Thyroid surgery risks accidental parathyroid injury, so watch for hypocalcemia and tetany, and keep calcium gluconate available.