16. Congenital Adrenal Hyperplasia (CAH) | 21-Hydroxylase, Lifelong Management | USMLE Step 1 скачать в хорошем качестве

16. Congenital Adrenal Hyperplasia (CAH) | 21-Hydroxylase, Lifelong Management | USMLE Step 1

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊 𝐘𝐨𝐮𝐭𝐮𝐛𝐞 :    / @draishwaryakelkar   📌𝗙𝗮𝗰𝗲𝗯𝗼𝗼𝗸 :   / draishwaryakelkar   📌𝗧𝘄𝗶𝘁𝘁𝗲𝗿:   / aishwayadr   📌𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 :   / clinical.learning   🧬 Congenital Adrenal Hyperplasia (CAH) | USMLE Step 1/2 CK | 21-Hydroxylase, Newborn Crisis, Labs & Lifelong Management Conquer Congenital Adrenal Hyperplasia (CAH) with a clean, exam-ready pathway that links enzyme blocks to hormones, phenotypes, and treatment. CAH is an autosomal recessive adrenal steroidogenesis defect; 21-hydroxylase (CYP21A2) deficiency causes ≈90–95% of cases. Loss of 21-OH → ↓cortisol ± ↓aldosterone, ↑ACTH (adrenal hyperplasia), shunting to androgens. Clinical patterns fall on a spectrum: salt-wasting (severe; vomiting, dehydration, hypotension, hyperkalemia, hyponatremia in the first 1–3 weeks), simple virilizing (no crisis but early virilization), and nonclassical (milder hyperandrogenism later with acne/hirsutism/oligo-ovulation). 46,XX infants may have ambiguous/virilized external genitalia with normal internal Müllerian organs; 46,XY infants can look normal at birth and crash with a salt-wasting crisis. High-yield labs: ↑17-hydroxyprogesterone, ↓cortisol, ↑ACTH, ±↓aldosterone/↑renin; newborn screens measure 17-OHP and are confirmed by ACTH stimulation testing. Know the enzyme triad for vignettes: “21 = salt-wasting & virilization”, “11β-hydroxylase = HTN/hypokalemia from excess DOC + virilization (↑11-deoxycortisol)”, “17α-hydroxylase = HTN/hypokalemia + sexual infantilism (↓androgens; 46,XY undervirilized, 46,XX primary amenorrhea)”; 3β-HSD deficiency lowers all steroids with ambiguous genitalia in both sexes and possible salt-wasting. Imaging is rarely first-line; prioritize electrolytes, glucose, acid–base, and endocrine labs in unstable neonates. Management is mechanism-driven and time-sensitive. In adrenal crisis, give rapid isotonic fluids, dextrose if hypoglycemic, correct electrolytes (treat hyperkalemia), and start stress-dose IV hydrocortisone immediately. Chronic therapy for 21-OH deficiency centers on physiologic glucocorticoid replacement (hydrocortisone in children; titrate to suppress excess ACTH/androgens without growth suppression), plus mineralocorticoid (fludrocortisone) and salt supplementation for salt-wasting forms. Teach sick-day steroid rules, provide an emergency hydrocortisone kit, and track growth, bone age, BP, renin, androstenedione/testosterone, and 17-OHP for dose calibration. Adolescents/adults may transition to longer-acting glucocorticoids (with caution), and females with significant virilization can consider multidisciplinary genital reconstructive options with shared decision-making. Address fertility (optimize hormonal control; counsel 46,XX on ovulatory function; screen 46,XY for testicular adrenal rest tumors), bone health, and psychosocial support. Exam pearls that always pay: newborn shock + hyperkalemia + hyponatremia = salt-wasting CAH until proven otherwise (treat first, confirm later); 17-OHP is the screening anchor; HTN + virilization → think 11β; HTN + undervirilized 46,XY → think 17α. This animation turns CAH into fast pattern recognition you can deploy on USMLE Step 1/2 CK and in Western pediatrics/EM/endocrine practice. SEO-Optimized Hashtags: #CongenitalAdrenalHyperplasia #CAH #USMLEStep1 #USMLEStep2CK #21HydroxylaseDeficiency #AdrenalCrisis #17OHP #PediatricEndocrinology #SaltWasting #Hyperkalemia #NewbornScreening #11BetaHydroxylase #17AlphaHydroxylase #Hirsutism #Virilization #Hydrocortisone #Fludrocortisone #MedicalEducationUSA #USMLEPreparation #Step2CKPrep