Endocrine System
The endocrine domain tests diabetes, thyroid disease, adrenal disorders, calcium metabolism, and pituitary disease, with emphasis on recognizing emergencies and avoiding overtreatment.
Core rules
- Type 2 diabetes: metformin remains initial therapy unless contraindicated. Add a GLP-1 receptor agonist or SGLT2 inhibitor when there is atherosclerotic cardiovascular disease, heart failure, or CKD. Check A1c and renal function regularly.
- Diabetic ketoacidosis: hyperglycemia, ketosis, and anion-gap metabolic acidosis. Treat with isotonic fluids, insulin infusion, and potassium replacement. Total-body potassium is depleted even when serum potassium is normal or high.
- Primary hypothyroidism: elevated TSH with low free T4. Treat with levothyroxine; recheck TSH in six to eight weeks. Do not treat subclinical hypothyroidism routinely unless TSH is persistently above 10 or the patient is symptomatic.
- Adrenal crisis: hypotension, hyponatremia, hyperkalemia, and shock. Give hydrocortisone immediately after drawing cortisol if there is clinical suspicion; do not wait for results.
Worked example
A 34-year-old woman has weight loss, heat intolerance, palpitations, a suppressed TSH, and elevated free T4. This is Graves disease. Start a beta blocker for symptoms and methimazole for thyroid hormone synthesis. Assess for thyroid storm if fever, agitation, or heart failure is present.
Traps
- Missing adrenal crisis because the cortisol result is pending.
- Using only sliding-scale insulin in DKA instead of fluids, insulin, and potassium management.
- Treating subclinical hypothyroidism without indication.
- Missing thyroid storm in a febrile, agitated patient with thyrotoxicosis.