8.1 Medical Disorders Overview

Endocrine Emergencies: The Core of Medical Disorders

The Medical Disorders domain is roughly 10% of the CEN blueprint, and endocrine crises are its highest-yield content because they hinge on exact lab numbers and a fixed treatment order. The two hyperglycemic emergencies—diabetic ketoacidosis (DKA) and the hyperosmolar hyperglycemic state (HHS)—sit on the same spectrum of insulin deficiency but diverge sharply on acidosis, ketones, and osmolality.

Under the 2024 ADA/AACE consensus, DKA requires three things at once: a D criterion (glucose ≥200 mg/dL or a known diabetes history—note this is lower than the older 250 mg/dL cutoff, and recognizes euglycemic DKA from SGLT2 inhibitors), a K criterion (beta-hydroxybutyrate ≥3.0 mmol/L or moderate-to-large ketonuria), and an A criterion of acidosis (venous pH <7.3 and/or bicarbonate <18 mEq/L).

DKA and HHS: Treatment Sequence and the Potassium Trap

Management of both crises is fluids first, then potassium check, then insulin. Begin with isotonic 0.9% normal saline, often 15–20 mL/kg in the first hour, because the average DKA fluid deficit is 6 L and HHS deficits reach 9–12 L. The single most tested safety rule: do not start insulin until serum potassium is ≥3.3 mEq/L. Total-body potassium is always depleted, but acidosis shifts it extracellularly, so the measured serum value looks normal or high. Insulin and correction of acidosis drive potassium back into cells, and starting insulin into a low-normal potassium can trigger lethal hypokalemia and arrhythmia.

Start a regular insulin infusion at ~0.1 unit/kg/hr (an initial bolus is optional and often omitted). When glucose falls to about 200 mg/dL in DKA (250–300 in HHS), add dextrose to the fluids and continue insulin—you treat ketoacidosis and osmolality, not just the glucose number. DKA resolves when glucose <200 mg/dL plus two of: bicarbonate ≥15 mEq/L, venous pH >7.3, or anion gap ≤12 mEq/L. Bicarbonate therapy is reserved for pH <6.9. Watch for cerebral edema, especially in younger patients with too-rapid correction.

Hypoglycemia is the mirror image: glucose <70 mg/dL with adrenergic (diaphoresis, tremor, tachycardia) or neuroglycopenic (confusion, seizure) signs. If the patient can swallow, give 15–20 g oral fast carbohydrate and recheck in 15 minutes. If unconscious or NPO, give IV D50 (25 g dextrose), or IM/SC glucagon 1 mg when no IV access exists.

Thyroid, Myxedema, and Adrenal Crises

Thyroid storm is decompensated thyrotoxicosis: high fever, tachycardia or atrial fibrillation, agitation or delirium, and GI or hepatic dysfunction. The Burch-Wartofsky Point Scale quantifies likelihood—≥45 strongly suggests storm, 25–44 is impending. The treatment order matters on the exam:

1. Beta-blocker (propranolol) for adrenergic control; propranolol also blocks peripheral T4→T3 conversion.
2. Thionamide—PTU (propylthiouracil) is preferred in storm because it blocks peripheral conversion.
3. Iodine (SSKI/Lugol’s) given at least 1 hour AFTER the thionamide—give iodine first and you fuel new hormone synthesis.
4. Glucocorticoids (hydrocortisone) and active cooling.

Myxedema coma is the opposite extreme: severe hypothyroidism producing hypothermia, bradycardia, hypotension, hyponatremia, and altered mentation, often in an elderly patient in winter. Treatment is IV levothyroxine, IV hydrocortisone (give steroids before/with thyroid hormone to avoid precipitating adrenal crisis), passive rewarming, and ventilatory support.

Adrenal (Addisonian) crisis is acute cortisol deficiency: hypotension refractory to fluids, hyponatremia, hyperkalemia, hypoglycemia, and weakness, often triggered by infection or abrupt steroid withdrawal. Treat with IV hydrocortisone 100 mg stat plus rapid 0.9% saline; do not delay steroids waiting on a cortisol level. Memorizing the low-sodium/high-potassium pairing separates adrenal crisis from other shock states on the exam.

Precipitants, Pitfalls, and Quick Differentiation

Knowing what triggers each crisis helps you choose the right answer when a stem buries the diagnosis in a history. DKA in a known diabetic is most often precipitated by infection or insulin noncompliance, while a first presentation may be new-onset type 1 diabetes. HHS classically strikes an older type 2 diabetic with limited access to water, often during an infection or after a new medication such as a steroid or diuretic.

Thyroid storm is precipitated by infection, surgery, trauma, iodine load, or abrupt antithyroid-drug discontinuation; adrenal crisis follows infection, surgery, or—most commonly tested—abrupt withdrawal of chronic steroids.

Several exam pitfalls recur. First, in hyperglycemic crises the glucose number is not the treatment endpoint—closing the anion gap (DKA) and correcting osmolality and dehydration (HHS) are. Second, hypoglycemia can mimic stroke or intoxication; a fingerstick glucose is mandatory on any patient with altered mental status, and you never withhold dextrose from an unresponsive patient waiting on labs. Third, the steroid-before-thyroid-hormone rule in myxedema and the thionamide-before-iodine rule in thyroid storm are sequence questions that reward memorizing order, not just drugs.

When two endocrine answers look plausible, anchor on the discriminating lab: ketones and a low pH point to DKA; a sky-high glucose with osmolality >320 and a near-normal pH points to HHS; low sodium with high potassium points to adrenal crisis; hypothermia with bradycardia points to myxedema; fever with tachyarrhythmia and agitation points to thyroid storm. These five lab-and-vital signatures resolve most of the look-alike traps in this domain.