Endocrine System
Core concepts
Diabetes emergencies: diabetic ketoacidosis shows glucose above 250, arterial pH below 7.3, bicarbonate below 18, an elevated anion gap, and ketones; total body potassium is depleted even when the serum value looks normal, so replace potassium once it falls below 5.3 and add dextrose when glucose reaches roughly 200 to 250. Hyperosmolar hyperglycemic state shows glucose above 600 with minimal ketosis and profound dehydration.
Thyroid: Graves disease causes a diffuse goiter, ophthalmopathy, and a suppressed TSH with elevated free T4. Thyroid storm is fever, tachycardia, altered mentation, and gastrointestinal symptoms; treat with a beta blocker, thioamide first, iodine only after the thioamide, glucocorticoid, and supportive care. Myxedema coma is hypothermia, bradycardia, hyponatremia, and hypoventilation; give levothyroxine together with hydrocortisone so you do not precipitate adrenal crisis.
Adrenal: primary adrenal insufficiency causes hyperkalemia, hyponatremia, hypotension, and hyperpigmentation with elevated ACTH. Primary hyperaldosteronism causes hypertension with hypokalemia and suppressed renin. Pheochromocytoma gives episodic headache, sweating, and palpitations; block alpha receptors before beta receptors.
Calcium: primary hyperparathyroidism, with high calcium, low phosphate, and high parathyroid hormone, is the most common outpatient cause of hypercalcemia. Hypocalcemia produces Chvostek and Trousseau signs and a prolonged QT interval.
Traps
- Giving iodine before a thioamide in thyroid storm.
- Giving levothyroxine before glucocorticoid in suspected myxedema with adrenal insufficiency.
- Attributing hyperkalemia and hyponatremia to kidney disease while missing adrenal insufficiency.
Rule of thumb
Hyperkalemia plus hyponatremia plus hypotension equals adrenal insufficiency; draw cortisol and give dexamethasone before thyroid hormone in any hypothyroid patient who is shocky.