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Dr. Parag H. Mehta
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Board Review · Medicine Simplified

Endocrinology

5 high-yield topics. Open a topic to review its pearls.

Disorders of Calcium

Hyper and hypocalcemia

Hypercalcemia Workup

  • High PTH: primary hyperparathyroidism, lithium, familial hypocalciuric hypercalcemia
  • Low PTH: malignancy (PTHrP), sarcoid (high 1,25-OH vitamin D), vitamin D toxicity
  • Familial hypocalciuric hypercalcemia: family history, low 24h urine calcium

Primary Hyperparathyroidism

  • Stones, bones, moans, abdominal groans
  • High urine and serum Ca, low PO4, high PTH, high ALP
  • X-ray: subperiosteal resorption, osteitis fibrosa cystica

Parathyroidectomy Indications

  • Symptomatic (osteoporosis, T-score under -2.5)
  • Renal stones
  • Age under 50
  • Calcium over 1 mg above normal (about 11.5)
  • Urine Ca over 400 mg/d
  • Impaired renal function (CrCl reduced 30 percent)

Non-Surgical Hypercalcemia Treatment

  • Hydration with 0.9 percent NaCl first
  • Loop diuretics once euvolemic
  • Bisphosphonates (full effect 48h)
  • Calcitonin (bridge until bisphosphonates work)

MEN Syndromes

  • MEN I (PPP): hyperParathyroid, Pituitary, Pancreatic tumors
  • MEN IIa (PPM): hyperParathyroid, Pheochromocytoma, Medullary carcinoma
  • MEN IIb (PMM): Pheochromocytoma, Medullary carcinoma, Mucosal neuromas

Thyroid Disorders

Hypo, hyper, nodules, cancer

Testing Principles

  • Best screen: TSH
  • Follow hypothyroidism: TSH (unless hypopituitary use free T4)
  • Follow hyperthyroidism: free T3 or free T4

Hypothyroidism

  • Cold intolerance, coarse features, delayed reflex relaxation, elevated prolactin
  • Primary: high TSH, low T4, treat with levothyroxine
  • Subclinical: high TSH, normal T4
  • Missed doses: resume home dose (half-life 7 days), no loading needed
  • Myxedema coma: IV hydrocortisone, IV levothyroxine, antibiotics

Hyperthyroidism

  • Heat intolerance, weight loss, tremor, palpitations
  • Graves: TSI/TRAb positive, diffuse uptake, exophthalmos
  • Treatment: PTU (pregnancy), methimazole, beta blocker
  • RAIU increased (Graves, toxic nodular); decreased (thyroiditis, amiodarone, exogenous)

Thyroid Storm

  • Precipitated by surgery, infection, contrast dye, withdrawal of antithyroid drugs
  • Fever, tachycardia, AF, CHF, CNS disturbance
  • Treatment: propranolol, hydrocortisone, PTU/methimazole THEN iodine

Nodules and Cancer

  • FNA is test of choice; do when TSH under 0.1
  • Papillary: most common, lymphatic spread
  • Follicular: hematogenous spread
  • Medullary: elevated calcitonin (MEN II)
  • Thyroglobulin for follow-up of thyroid cancer

Adrenal Disorders

Cushing, Addison, Conn, pheo

Cushing Syndrome

  • Weakness, hirsutism, HTN, moon facies, buffalo hump, purple striae, easy bruising
  • Screening: 24h urine cortisol or PM salivary cortisol
  • Confirm: low-dose dexamethasone suppression test
  • Measure ACTH: high means pituitary or ectopic; low means adrenal (CT abdomen)

Primary Adrenal Insufficiency

  • Weakness, weight loss, abdominal pain, hypotension
  • Low Na, high K, low glucose, eosinophilia
  • Acute crisis: IV hydrocortisone
  • Stress dose steroids for trauma, surgery, infection

Primary Hyperaldosteronism

  • HTN, hypokalemia, metabolic alkalosis
  • Screen: aldosterone/renin ratio over 20
  • Adenoma (Conn): surgical resection
  • Bilateral hyperplasia: spironolactone

Pheochromocytoma

  • Paroxysmal HTN, triad: headache, palpitations, diaphoresis
  • Screen: plasma metanephrines
  • Localize: CT/MRI, then MIBG scan if negative
  • Alpha blockade before surgery (before beta blockade)

Pituitary Disorders

Adenomas, prolactinoma, acromegaly

Prolactinoma

  • Prolactin suppresses GnRH: impotence (male), amenorrhea/galactorrhea (female)
  • Check TSH to rule out hypothyroidism first
  • Prolactin over 200 is macroadenoma; under 200 microadenoma
  • Treatment: dopamine agonists (bromocriptine, cabergoline)

Acromegaly

  • Increased hat/shoe/ring size, coarse features, macroglossia
  • Colon polyps: screening colonoscopy; OSA; DM
  • Best screen: IGF-1 (random GH not helpful)
  • Confirm: oral glucose suppression test
  • Treatment: transsphenoidal surgery, octreotide, dopamine agonists

Pituitary Apoplexy

  • Hemorrhagic infarction of pituitary tumor
  • Severe headache, N/V, visual defects, altered MS
  • Treatment: stress dose steroids, neurosurgical decompression if visual defects
  • Sheehan syndrome: postpartum hypopituitarism from blood loss

Diabetes Mellitus

Diagnosis, treatment, complications

Diagnosis

  • Fasting BS 126 or more x2, random over 200 x2, A1C over 6.5, 2h GTT over 200
  • Impaired fasting: 100-125; impaired glucose tolerance: 140-199
  • Screen every 3 years starting age 45
  • Type 1 vs 2: check GAD antibodies and islet cell antibodies

Oral Agents

  • Metformin: weight neutral, no hypoglycemia; avoid in renal insufficiency, CHF; hold before contrast
  • Sulfonylureas: hypoglycemia, weight gain
  • GLP-1 (exenatide): weight loss, no hypoglycemia
  • SGLT2i and DPP-4 inhibitors also used
  • Most cause weight gain EXCEPT metformin, incretins, amylin analogues

Targets

  • A1C under 7
  • Preprandial 90-130, postprandial under 180
  • BP under 130/80, LDL under 70-100
  • Yearly eye exam, yearly lipid, semiannual microalbumin, quarterly A1C

Complications

  • Retinopathy: leading cause of blindness in adults
  • Nephropathy: leading cause of ESRD; ACEI/ARB
  • Neuropathy: gabapentin/TCA; gastroparesis with prokinetics
  • Dawn phenomenon: increase nighttime long-acting insulin
  • Somogyi effect: decrease nighttime long-acting insulin

Emergencies

  • DKA: pH under 7.3, HCO3 under 15, anion gap; IVF, insulin, add dextrose at glucose 250
  • Follow pH and anion gap q4h until gap closes
  • HHNK: glucose over 600, osm over 310, no ketosis; aggressive fluids
  • Give long-acting SC insulin before stopping IV insulin