Adrenal Steroids & CAH — USMLE Step 1 Quiz

Adrenal Cortex Zones — GFR = Salt, Sugar, Sex

Zone	Product	Regulation
Zona Glomerulosa	Aldosterone (Mineralocorticoids)	RAAS, K⁺
Zona Fasciculata	Cortisol (Glucocorticoids)	ACTH (HPA axis)
Zona Reticularis	DHEA, Androstenedione	ACTH

⚡ HIGH-YIELD: The zona glomerulosa is the ONLY zone regulated by RAAS. It LACKS 17α-hydroxylase → cannot make cortisol or androgens.

Venous Drainage

Right adrenal vein → directly into IVC.
Left adrenal vein → left renal vein (then IVC). The left gonadal vein also drains into the left renal vein.

⚡ Left adrenal vein drains into the left renal vein, not the IVC. This is frequently tested alongside left varicocele anatomy.

Medulla vs Cortex

Cortex: derived from mesoderm, produces steroid hormones (mineralocorticoids, glucocorticoids, androgens).
Medulla: derived from neural crest (ectoderm), produces catecholamines (epinephrine > norepinephrine).

Rate-Limiting Step

StAR protein transports cholesterol from outer → inner mitochondrial membrane. This is the rate-limiting step for ALL steroid hormone synthesis. CYP11A1 (desmolase) then cleaves cholesterol to pregnenolone.

⚡ StAR = rate-limiting step. Deficiency = Lipoid CAH (nothing gets made).

Key Enzymes

Enzyme	Gene	Reaction	Key Point
StAR	STAR	Cholesterol into mitochondria	Rate-limiting step
Desmolase (SCC)	CYP11A1	Cholesterol → Pregnenolone	First enzymatic step
3β-HSD	HSD3B2	Δ5 → Δ4 steroids (all zones)	Required in ALL zones
17α-hydroxylase	CYP17A1	Pregnenolone/Prog → 17-OH forms	ABSENT in glomerulosa
17,20-lyase	CYP17A1	17-OH-Preg → DHEA	Same protein as 17α-OH
21-hydroxylase	CYP21A2	Prog → DOC; 17-OH-Prog → 11-deoxycortisol	Most common CAH deficiency
11β-hydroxylase	CYP11B1	11-deoxycortisol → Cortisol; DOC → Corticosterone	2nd most common CAH
Aldosterone synthase	CYP11B2	Corticosterone → Aldosterone	Only in glomerulosa

Zone-by-Zone Pathways

Glomerulosa (Aldosterone):
Cholesterol → Pregnenolone → Progesterone → DOC → Corticosterone → Aldosterone
No 17α-hydroxylase in this zone.

Fasciculata (Cortisol):
Cholesterol → Pregnenolone → 17-OH-Pregnenolone → 17-OH-Progesterone → 11-deoxycortisol → Cortisol

Reticularis (Androgens):
Cholesterol → Pregnenolone → 17-OH-Pregnenolone → DHEA → Androstenedione
DHEA-S is the most abundant circulating adrenal androgen and the best marker of adrenal androgen production.

CAH Master Comparison Table

⚡ MEMORIZE THIS TABLE. Almost every CAH board question can be answered from it.

Feature	21-OHD	11β-OHD	17α-OHD	3β-HSD	StAR/SCC
Cortisol	↓↓	↓↓	↓↓	↓↓	↓↓↓
Aldosterone	↓↓	↓ (low)	↓ (low)	↓↓	↓↓↓
MC effect	↓ Salt wasting	↑ HTN (DOC)	↑ HTN (DOC)	↓ Salt wasting	↓ Salt wasting
Blood Pressure	Low / crisis	↑ Hypertension	↑ Hypertension	Low / crisis	Low / crisis
Androgens	↑↑	↑↑	↓↓↓	↓ T, ↑ DHEA	↓↓↓
K⁺	↑ Hyperkalemia	↓ Hypokalemia	↓ Hypokalemia	↑ Hyperkalemia	↑ Hyperkalemia
XX phenotype	Virilized	Virilized	Normal ♀, no puberty	Mildly virilized	Phenotypic ♀
XY phenotype	Normal ♂	Normal ♂	Phenotypic ♀	Undervirilized	Phenotypic ♀
Key marker	↑↑ 17-OHP	↑ 11-deoxycortisol, ↑ DOC	↑ Corticosterone, ↑ DOC	↑ DHEA	All steroids ↓
Frequency	~95%	~5-8%	Rare	Rare	Very rare

⚡ Rule of thumb: HTN-causing CAH = 11β-OHD and 17α-OHD (DOC accumulates). Salt-wasting CAH = 21-OHD, 3β-HSD, StAR.

21-Hydroxylase Deficiency (CYP21A2)

~95% of all CAH. Gene: CYP21A2, chromosome 6p21, within the HLA complex (linked to HLA-Bw47). The most commonly tested CAH on board exams.

Block Biochemistry

Cannot convert progesterone → DOC or 17-OH-progesterone → 11-deoxycortisol.
Result: ↓ Cortisol, ↓ Aldosterone, ↑↑ Androgens, ↑↑↑ 17-OHP

⚡ Diagnostic marker = 17-hydroxyprogesterone (17-OHP). Included in all US newborn screening panels.

Clinical Subtypes

Classic Salt-Wasting (~75%): Adrenal crisis in first 1–2 weeks (hyponatremia, hyperkalemia, hypotension). XX females: ambiguous genitalia (clitoromegaly, labial fusion). XY males: look normal at birth → crisis!
Classic Simple Virilizing (~25%): Partial enzyme activity. Females: ambiguous genitalia. Both sexes: precocious puberty → early epiphyseal closure → SHORT adult stature despite tall childhood.
Non-Classic (Late-Onset): Hirsutism, acne, oligomenorrhea in adolescence/adulthood. Mimics PCOS. Diagnosed by exaggerated 17-OHP response to ACTH stimulation test.

Treatment

Glucocorticoid: Hydrocortisone in children (least growth suppression; short half-life mimics physiology)
Mineralocorticoid: Fludrocortisone for salt-wasting forms
Stress dosing: Required during illness/surgery

11β-Hydroxylase Deficiency (CYP11B1)

~5–8% of CAH. Second most common form.

Block Biochemistry

Cannot convert 11-deoxycortisol → cortisol or DOC → corticosterone.
Result: ↓ Cortisol, ↑↑↑ DOC (potent mineralocorticoid), ↑↑ Androgens, ↑↑ 11-deoxycortisol

⚡ KEY DIFFERENTIATOR: 11β-OHD = Virilization + HYPERTENSION.
21-OHD = virilization + salt wasting (hypotension).
DOC accumulation drives the HTN + hypokalemia. Aldosterone is actually low (renin suppressed by DOC-mediated volume expansion).

Clinical Features

Hypertension + hypokalemia (DOC excess)
Virilization in XX females (ambiguous genitalia)
Precocious puberty in both sexes
↓ Aldosterone, ↓ Renin (suppressed by DOC)

Treatment

Glucocorticoid replacement suppresses ACTH → reduces DOC and androgen overproduction → resolves HTN. Mineralocorticoid replacement NOT needed (the problem is excess MC, not deficiency).

17α-Hydroxylase Deficiency (CYP17A1)

CYP17A1 encodes both 17α-hydroxylase and 17,20-lyase activities. It is absent in the zona glomerulosa (why aldosterone is unaffected by this enzyme).

Block Biochemistry

Cannot make cortisol (no 17-OH intermediates) or any sex steroids (no DHEA, no androstenedione).
Precursors shunt → corticosterone and DOC (mineralocorticoids).
Result: ↓ Cortisol, ↓↓↓ All sex steroids, ↑↑ DOC/Corticosterone → HTN + hypokalemia

⚡ 17α-OHD = HTN + Sexual Infantilism (no sex steroids).
XY individuals: phenotypically female (testes present, no uterus because AMH still made by Sertoli cells).
XX individuals: normal female genitalia at birth but no puberty (no estrogens).

Feature	11β-OHD	17α-OHD
Blood Pressure	↑ HTN	↑ HTN
Androgens	↑↑ (virilization)	↓↓ (undervirilization)
XX phenotype	Virilized	Normal ♀, no puberty
XY phenotype	Normal ♂	Phenotypic ♀

3β-Hydroxysteroid Dehydrogenase Deficiency

3β-HSD converts Δ5 → Δ4 steroids in ALL zones. Required for aldosterone, cortisol, and potent androgens.

Cortisol: ↓↓ | Aldosterone: ↓↓ → salt wasting
Testosterone: ↓↓ | DHEA: ↑↑↑ (accumulates)

⚡ UNIQUE: Both sexes have ambiguous genitalia.
XX females: mildly virilized (DHEA is a weak androgen).
XY males: undervirilized/hypospadias (can't make testosterone).
Plus salt wasting (no aldosterone).

Lipoid CAH (StAR Protein / CYP11A1 Deficiency)

StAR failure → cholesterol cannot enter mitochondria → no steroid hormones synthesized at all. Cholesterol esters accumulate → lipid-laden adrenals.

All steroids absent (cortisol, aldosterone, sex steroids)
All patients phenotypically female (XY: completely undervirilized)
Severe salt wasting → often fatal without treatment
Lipid-laden, enlarged adrenal glands on imaging

⚡ Lipoid CAH = most severe form. All steroids absent. All phenotypic females. Severe salt wasting. "Nothing gets made."

HPA Axis

CRH (hypothalamus) → ACTH (anterior pituitary corticotrophs) → Cortisol (zona fasciculata). Cortisol provides negative feedback on both hypothalamus and pituitary.

ACTH is derived from POMC → also cleaved to produce α-MSH. Excess ACTH = excess α-MSH → hyperpigmentation (skin creases, buccal mucosa). Occurs in primary adrenal insufficiency and ectopic ACTH.

Diurnal rhythm: Cortisol peaks ~8 AM, lowest at midnight (suprachiasmatic nucleus).

Cushing Syndrome Workup

Step 1 (confirm hypercortisolism): 24-hr urine free cortisol, late-night salivary cortisol, or 1 mg overnight dexamethasone suppression test.
Step 2 (ACTH-dependent?): Measure ACTH. Low ACTH = adrenal tumor (autonomous). High ACTH = pituitary vs. ectopic.
Step 3 (localize): High-dose dexamethasone: pituitary adenoma suppresses (partially); ectopic does NOT suppress. CRH test: pituitary responds with ↑ACTH; ectopic does not.

⚡ Low ACTH + Cushing = adrenal adenoma/carcinoma or exogenous steroids.
High ACTH + Cushing + suppresses on high-dose dex = pituitary adenoma (Cushing disease).
High ACTH + Cushing + does NOT suppress = ectopic (e.g., small cell lung Ca).

CBC Pattern with Glucocorticoids

Neutrophilia (demargination) + Lymphopenia (apoptosis/redistribution) + Eosinopenia (sequestration). Monocytes also decrease.

⚡ Mnemonic: "Cortisol makes Neutrophils Numerous, but Lymphocytes, Eosinophils, and Monocytes Low."

Glucocorticoid-Induced Osteoporosis

Mechanisms: inhibition of osteoblasts, ↓ intestinal calcium absorption, ↑ renal calcium excretion → secondary hyperparathyroidism → accelerated bone resorption. Most common cause of secondary osteoporosis.

Aldosterone — Regulation & Action

Produced exclusively in zona glomerulosa. Regulated primarily by RAAS and serum K⁺. ACTH has a minor permissive role only.

Mechanism: Binds intracellular mineralocorticoid receptor (MR) in principal cells of cortical collecting duct → ↑ ENaC and Na⁺/K⁺-ATPase → Na⁺ reabsorption, K⁺ and H⁺ secretion.

⚡ Aldosterone excess → hypokalemia + metabolic alkalosis (Na⁺ in, K⁺/H⁺ out).
Aldosterone deficiency → hyperkalemia + metabolic acidosis.

11β-HSD2 — The Cortisol Gatekeeper

11β-HSD2 in renal principal cells converts cortisol → cortisone (inactive at MR), preventing cortisol from activating MR. Without it, high-concentration cortisol activates MR → apparent mineralocorticoid excess.

⚡ Licorice (glycyrrhizic acid) inhibits 11β-HSD2 → cortisol activates MR → HTN + hypokalemia with LOW aldosterone and LOW renin. This pattern = apparent mineralocorticoid excess (AME).

Primary vs Secondary Hyperaldosteronism

Feature	Primary (Conn)	Secondary
Aldosterone	↑	↑
Renin	↓ (suppressed)	↑ (elevated)
Cause	Adrenal adenoma or bilateral hyperplasia	Renal artery stenosis, CHF, cirrhosis
Treatment	Adrenalectomy (adenoma) or Spironolactone/Eplerenone (bilateral)	Treat underlying cause

Primary vs Secondary Adrenal Insufficiency

Feature	Primary (Addison)	Secondary
Cortisol	↓↓	↓↓
ACTH	↑↑	↓↓
Aldosterone	↓ (salt wasting)	Normal (RAAS intact)
Hyperpigmentation	YES (↑ ACTH/MSH)	NO
Hyperkalemia	YES	NO

⚡ KEY: Primary = aldosterone lost (hyperkalemia, salt wasting) + ACTH high (hyperpigmentation).
Secondary = aldosterone preserved (RAAS intact). Both have hypotension, fatigue, hypoglycemia.

Causes of Primary Adrenal Insufficiency

Autoimmune adrenalitis (most common in developed world)
Tuberculosis (most common worldwide)
Waterhouse-Friderichsen syndrome (bilateral adrenal hemorrhage from N. meningitidis sepsis)
Metastatic disease

Most Common Cause of Adrenal Insufficiency Overall

Chronic exogenous glucocorticoid use → HPA axis suppression. Abrupt cessation → acute adrenal crisis. Never stop glucocorticoids abruptly — always taper.

ACTH Stimulation Test (Cosyntropin)

In primary adrenal insufficiency: adrenals are damaged → cortisol fails to rise (remains low) after cosyntropin administration.
Normal response: cortisol rises above 18–20 μg/dL at 60 minutes.

Glucocorticoid Drugs

Drug	GC Potency	MC Potency	Duration	Use
Hydrocortisone	1x	1x	Short ~8h	Adrenal insufficiency, CAH in children (least growth suppression)
Prednisone	4x	0.8x	Intermediate	Autoimmune/inflammatory
Dexamethasone	30x	0	Long ~36h	Cerebral edema, dex suppression test, prenatal CAH; zero MC activity
Fludrocortisone	10x	125x	Intermediate	Mineralocorticoid replacement (Addison, salt-wasting CAH)
Betamethasone	25x	0	Long	Fetal lung maturity (surfactant induction in preterm labor)

⚡ Dexamethasone: highest GC potency, ZERO MC activity → ideal for suppression tests and cerebral edema.
⚡ Fludrocortisone: highest MC potency → mineralocorticoid replacement.
⚡ Hydrocortisone: preferred in children (least growth suppression).

Mineralocorticoid Receptor Antagonists

Spironolactone: Non-selective MR antagonist; also blocks androgen receptors + inhibits steroidogenesis → useful for hirsutism/PCOS. Side effects: gynecomastia in males, hyperkalemia.
Eplerenone: Selective MR antagonist — no anti-androgen effects → no gynecomastia. Used post-MI with reduced EF.

Steroidogenesis Inhibitors

Ketoconazole: Inhibits multiple CYP enzymes (desmolase, 17α-OH, 11β-OH). Used in Cushing syndrome. Also inhibits fungal CYP51.
Metyrapone: Inhibits 11β-hydroxylase. Used in metyrapone stimulation test (tests ACTH reserve) and Cushing syndrome. Expect ↑ 11-deoxycortisol and ↑ ACTH if pituitary is intact.
Aminoglutethimide: Inhibits cholesterol desmolase (first step).
Mitotane: Adrenolytic — directly destroys adrenal cortical cells. Used in adrenocortical carcinoma.

Pheochromocytoma Management

⚡ Alpha-blockade FIRST (phenoxybenzamine), then beta-blockade if needed.
NEVER give beta-blockers first → unopposed alpha-adrenergic stimulation → life-threatening hypertensive crisis.

Chronic Glucocorticoid Side Effects

Cushing syndrome features (central obesity, moon facies, striae, easy bruising)
Osteoporosis (most common cause of secondary osteoporosis)
Hyperglycemia / diabetes
Avascular necrosis of femoral head
Cataracts (posterior subcapsular)
PUD (especially with NSAIDs)
Growth suppression in children
HPA suppression → must TAPER, never stop abruptly

⚡ Board Pearls — Quick-Fire Review

Newborn + ambiguous genitalia + hyponatremia + hyperkalemia → 21-hydroxylase deficiency (salt-wasting CAH). Check 17-OHP.
Newborn + ambiguous genitalia + hypertension + hypokalemia → 11β-hydroxylase deficiency. DOC excess causes HTN.
Adolescent XY + female phenotype + HTN + no secondary sex characteristics → 17α-hydroxylase deficiency.
Both XX and XY newborns with ambiguous genitalia + salt wasting → 3β-HSD deficiency. DHEA mildly virilizes XX; testosterone deficiency undervirilizes XY.
Infant + salt wasting + all phenotypically female + lipid-laden adrenals → Lipoid CAH (StAR mutation).
Woman + hirsutism + elevated 17-OHP after ACTH stim + normal BP → Non-classic (late-onset) 21-OHD.
Hyperpigmented patient + hypotension + hyperkalemia → Primary adrenal insufficiency (Addison disease). ACTH is high.
Patient on chronic prednisone suddenly stops medication → Adrenal crisis. The HPA axis is suppressed.
Licorice ingestion + HTN + hypokalemia + LOW aldosterone + LOW renin → 11β-HSD2 inhibition (Apparent Mineralocorticoid Excess). Cortisol activates MR.
Cushing + LOW ACTH → Adrenal adenoma/carcinoma (ACTH-independent). HIGH ACTH → pituitary (disease) or ectopic (small cell lung Ca).
Cushing + HIGH ACTH + does NOT suppress on high-dose dexamethasone → Ectopic ACTH (e.g., small cell lung cancer).
Cushing + HIGH ACTH + DOES suppress on high-dose dexamethasone → Pituitary adenoma (Cushing disease).
Waterhouse-Friderichsen syndrome = bilateral adrenal hemorrhage from N. meningitidis septicemia → acute adrenal insufficiency.
Most common cause of adrenal insufficiency overall = chronic exogenous glucocorticoid use.
Most common cause of PRIMARY adrenal insufficiency (developed world) = autoimmune adrenalitis.
Drug to inhibit 11β-hydroxylase to test ACTH reserve = Metyrapone. Expect ↑ 11-deoxycortisol and ↑ ACTH if pituitary is intact.
CAH gene on chromosome 6 in HLA complex = CYP21A2 (21-hydroxylase), linked to HLA-Bw47.
Rapid growth in childhood + accelerated bone age + short adult stature → Excess androgens cause premature epiphyseal closure in 21-OHD or 11β-OHD.
XY infant + all steroids absent + salt wasting + female phenotype → StAR protein deficiency (Lipoid CAH).
Spironolactone treats hirsutism in PCOS via androgen receptor antagonism and inhibition of steroidogenesis (not just MR antagonism).
Pheo preop: Alpha-block first (phenoxybenzamine), then beta-block. NEVER beta first → hypertensive crisis.
Left adrenal vein → left renal vein (not IVC). Right adrenal vein → IVC directly.
Cortisol CBC: Neutrophilia + Lymphopenia + Eosinopenia.
Rate-limiting step of steroidogenesis = StAR protein (cholesterol transport into mitochondria).
Hydrocortisone preferred in children with CAH because it causes the least growth suppression (short half-life, low potency, most physiologic).

Sodium (Na⁺)	136–146 mEq/L	136–146 mmol/L
Potassium (K⁺)	3.5–5.0 mEq/L	3.5–5.0 mmol/L
Chloride (Cl⁻)	95–105 mEq/L	95–105 mmol/L
Bicarbonate (HCO₃⁻)	22–28 mEq/L	22–28 mmol/L
Calcium	8.4–10.2 mg/dL	2.1–2.6 mmol/L
Magnesium (Mg²⁺)	1.5–2.0 mg/dL	0.75–1.0 mmol/L
Phosphorus (inorganic)	3.0–4.5 mg/dL	1.0–1.5 mmol/L

Urea nitrogen (BUN)	7–18 mg/dL	2.5–6.4 mmol/L
Creatinine	0.6–1.2 mg/dL	53–106 μmol/L
Glucose (fasting)	70–100 mg/dL	3.8–5.6 mmol/L
Glucose (random, non-fasting)	<140 mg/dL	<7.77 mmol/L
Osmolality	275–295 mOsmol/kg H₂O	275–295 mOsmol/kg H₂O
Uric acid	3.0–8.2 mg/dL	0.18–0.48 mmol/L
Creatinine clearance (male)	97–137 mL/min
Creatinine clearance (female)	88–128 mL/min

ALT (alanine aminotransferase)	10–40 U/L
AST (aspartate aminotransferase)	12–38 U/L
Alkaline phosphatase	25–100 U/L
Bilirubin, total	0.1–1.0 mg/dL	2–17 μmol/L
Bilirubin, direct	0.0–0.3 mg/dL	0–5 μmol/L
Proteins, total	6.0–7.8 g/dL	60–78 g/L
Albumin	3.5–5.5 g/dL	35–55 g/L
Globulin	2.3–3.5 g/dL	23–35 g/L

Amylase	25–125 U/L
Lipase	13–60 U/L
Creatine kinase (male)	25–90 U/L
Creatine kinase (female)	10–70 U/L
Lactate dehydrogenase	45–200 U/L
Troponin I	≤0.04 ng/mL	≤0.04 μg/L

IgA	76–390 mg/dL	0.76–3.90 g/L
IgE	0–380 IU/mL	0–380 kIU/L
IgG	650–1500 mg/dL	6.5–15.0 g/L
IgM	50–300 mg/dL	0.5–3.0 g/L

Adrenal Steroids & CAHUSMLE Step 1 — 30 Questions

Adrenal Steroids &
Congenital Adrenal Hyperplasias

Quiz Complete!

Cortisol (0800 h)	5–23 μg/dL	138–635 nmol/L
Cortisol (1600 h)	3–15 μg/dL	82–413 nmol/L
Cortisol (2000 h)	<50% of 0800 h
17-Hydroxycorticosteroids (male)	3.0–10.0 mg/24 h	8.2–27.6 μmol/24 h
17-Hydroxycorticosteroids (female)	2.0–8.0 mg/24 h	5.5–22.0 μmol/24 h
17-Ketosteroids, total (male)	8–20 mg/24 h	28–70 μmol/24 h
17-Ketosteroids, total (female)	6–15 mg/24 h	21–52 μmol/24 h

TSH	0.4–4.0 μU/mL	0.4–4.0 mIU/L
Triiodothyronine T3 (RIA)	100–200 ng/dL	1.5–3.1 nmol/L
T3 resin uptake	25%–35%	0.25–0.35
Thyroxine T4	5–12 μg/dL	64–155 nmol/L
Free T4	0.9–1.7 ng/dL	12.0–21.9 pmol/L
Thyroidal iodine (¹²³I) uptake	8%–30% / 24 h	0.08–0.30/24 h

FSH (male)	4–25 mIU/mL	4–25 IU/L
FSH (female, premenopause)	4–30 mIU/mL	4–30 IU/L
FSH (female, midcycle peak)	10–90 mIU/mL	10–90 IU/L
FSH (female, postmenopause)	40–250 mIU/mL	40–250 IU/L
LH (male)	6–23 mIU/mL	6–23 IU/L
LH (female, follicular)	5–30 mIU/mL	5–30 IU/L
LH (female, midcycle)	75–150 mIU/mL	75–150 IU/L
LH (female, postmenopause)	30–200 mIU/mL	30–200 IU/L
Prolactin (male)	<17 ng/mL	<17 μg/L
Prolactin (female)	<25 ng/mL	<25 μg/L

Intact PTH	10–60 pg/mL	10–60 ng/L
Growth hormone (fasting)	<5 ng/mL	<5 μg/L
Growth hormone (provocative stimuli)	>7 ng/mL	>7 μg/L
Hemoglobin A1c	≤6%	≤42 mmol/mol

Total cholesterol (normal)	<200 mg/dL	<5.2 mmol/L
Total cholesterol (high)	>240 mg/dL	>6.2 mmol/L
HDL	40–60 mg/dL	1.0–1.6 mmol/L
LDL	<160 mg/dL	<4.2 mmol/L
Triglycerides (normal)	<150 mg/dL	<1.70 mmol/L
Triglycerides (borderline)	151–199 mg/dL	1.71–2.25 mmol/L

Ferritin (male)	20–250 ng/mL	20–250 μg/L
Ferritin (female)	10–120 ng/mL	10–120 μg/L
Iron (male)	65–175 μg/dL	11.6–31.3 μmol/L
Iron (female)	50–170 μg/dL	9.0–30.4 μmol/L
TIBC	250–400 μg/dL	44.8–71.6 μmol/L
Transferrin	200–360 mg/dL	2.0–3.6 g/L

Hematocrit (male)	41%–53%	0.41–0.53
Hematocrit (female)	36%–46%	0.36–0.46
Hemoglobin (male)	13.5–17.5 g/dL	135–175 g/L
Hemoglobin (female)	12.0–16.0 g/dL	120–160 g/L
MCV	80–100 μm³	80–100 fL
MCH	25–35 pg/cell	0.39–0.54 fmol/cell
MCHC	31%–36% Hb/cell	4.8–5.6 mmol Hb/L
WBC (leukocyte count)	4,500–11,000/mm³	4.5–11.0 × 10⁹/L
Platelet count	150,000–400,000/mm³	150–400 × 10⁹/L
RBC (male)	4.3–5.9 million/mm³	4.3–5.9 × 10¹²/L
RBC (female)	3.5–5.5 million/mm³	3.5–5.5 × 10¹²/L

Neutrophils, segmented	54%–62%	0.54–0.62
Neutrophils, bands	3%–5%	0.03–0.05
Lymphocytes	25%–33%	0.25–0.33
Monocytes	3%–7%	0.03–0.07
Eosinophils	1%–3%	0.01–0.03
Basophils	0%–0.75%	0.00–0.0075

Reticulocyte count	0.5%–1.5%	0.005–0.015
ESR (male)	0–15 mm/h
ESR (female)	0–20 mm/h
CD4+ T-lymphocyte count	≥500/mm³	≥0.5 × 10⁹/L

aPTT (activated PTT)	25–40 seconds
PT (prothrombin time)	11–15 seconds
D-dimer	≤250 ng/mL	≤1.4 nmol/L

Plasma volume (male)	25–43 mL/kg	0.025–0.043 L/kg
Plasma volume (female)	28–45 mL/kg	0.028–0.045 L/kg
Red cell volume (male)	20–36 mL/kg	0.020–0.036 L/kg
Red cell volume (female)	19–31 mL/kg	0.019–0.031 L/kg

PO₂	75–105 mm Hg	10.0–14.0 kPa
PCO₂	33–45 mm Hg	4.4–5.9 kPa
pH	7.35–7.45	[H⁺] 36–44 nmol/L

Cell count	0–5/mm³	0–5 × 10⁶/L
Chloride	118–132 mEq/L	118–132 mmol/L
Gamma globulin	3%–12% total proteins	0.03–0.12
Glucose	40–70 mg/dL	2.2–3.9 mmol/L
Pressure	70–180 mm H₂O
Proteins, total	<40 mg/dL	<0.40 g/L

Calcium	100–300 mg/24 h	2.5–7.5 mmol/24 h
Osmolality	50–1200 mOsmol/kg H₂O
Oxalate	8–40 μg/mL	90–445 μmol/L
Proteins, total	<150 mg/24 h	<0.15 g/24 h

Adrenal Steroids &Congenital Adrenal Hyperplasias

Quiz Complete!

Laboratory Reference Values

Electrolytes

Renal / Metabolic

Hepatic

Other Serum

Immunoglobulins

Adrenal / Stress Hormones

Thyroid

Gonadotropins & Reproductive

Other Endocrine

Cholesterol & Lipids

Iron Studies

Complete Blood Count

WBC Differential

Other Hematologic

Coagulation Studies

Volume

Arterial Blood Gas (Room Air)

Cerebrospinal Fluid (CSF)

Urine

Body Mass Index

Study Reference

Adrenal Cortex Zones — GFR = Salt, Sugar, Sex

Venous Drainage

Medulla vs Cortex

Rate-Limiting Step

Key Enzymes

Zone-by-Zone Pathways

CAH Master Comparison Table

21-Hydroxylase Deficiency (CYP21A2)

Block Biochemistry

Clinical Subtypes

Treatment

11β-Hydroxylase Deficiency (CYP11B1)

Block Biochemistry

Clinical Features

Treatment

17α-Hydroxylase Deficiency (CYP17A1)

Block Biochemistry

3β-Hydroxysteroid Dehydrogenase Deficiency

Lipoid CAH (StAR Protein / CYP11A1 Deficiency)

HPA Axis

Cushing Syndrome Workup

CBC Pattern with Glucocorticoids

Glucocorticoid-Induced Osteoporosis

Aldosterone — Regulation & Action

11β-HSD2 — The Cortisol Gatekeeper

Primary vs Secondary Hyperaldosteronism

Primary vs Secondary Adrenal Insufficiency

Causes of Primary Adrenal Insufficiency

Most Common Cause of Adrenal Insufficiency Overall

ACTH Stimulation Test (Cosyntropin)

Glucocorticoid Drugs

Mineralocorticoid Receptor Antagonists

Steroidogenesis Inhibitors

Pheochromocytoma Management

Chronic Glucocorticoid Side Effects

⚡ Board Pearls — Quick-Fire Review

Adrenal Steroids &
Congenital Adrenal Hyperplasias